As Many Exceptions As Rules

Water, Water Everywhere, But….

2012-02-22T07:00:00.022-05:00

Biology concepts – symbiosis, mutualism, water storage

“Gobi” means desert in Ural-Altaic,

so when you say, “Gobi Desert,” you

are really being redundant.

Sometimes the places with the most water are the most lifeless areas. Everyone thinks of sand and heat, but Lawrence of Arabia wouldn’t even recognize most biological deserts.

The term biological desert is misleading, since places like the Gobi Desert in Asia support over 600 species of plants and hundreds of animal species, vertebrate and invertebrate. Death Valley in the USA has over 100 plants species; it could hardly be called dead! A biological desert has less to do with the climate and more to do with the adaptability of organisms to adverse conditions of oxygen, salt, water, light, or too often - pollution.

Take for instance the South Pacific Gyre. This area of about 34 million square kilometers (10 million sq. miles) has very little life in the pelagic zone (the below the surface waters to just above the sea floor). In the last posts we learned why water and salts are crucial for life, and the extreme evolutionary adaptations that have occurred in many organisms in order to conserve body water and maintain safe salt levels. But here we are in the ocean – water everywhere, salt everywhere, but almost nothing lives in the gyre.

The north and south Pacific gyres represent

a huge portion of the Earth’s surface, and

these are relatively life free areas, the largest

deserts on Earth.

The reason for this paucity of life has more to do with nutrients than with water or salt. Because the current moves counter-clockwise, the center of the gyre is isolated from the upwelling of nutrients from the ocean floor, and the winds can’t help to churn the waters. Even if they could, it would help little. The waters of the gyre are rigidly layered due to salt and temperature differences (stratification, I Am Your Density), so nutrients find it difficult to travel to the surface from below. Adding to the problem, there is little landmass in the South Pacific, so windblown organic material and terrestrial runoff are limited. Nutrients are coming from neither above nor from below.

With limited nutrients, there is a ceiling to the amount of primary productivity of phytoplankton (phyto = plant, and planktos = wandering in Greek) that can take place. Fewer producers means that few primary consumers can be supported, and so forth up the food chain. Little life on the surface means few nutrients drop to the ocean floor (waste and dead organisms), and so on.

The ocean gyres have little upwelling if nutrients

and therefore little plankton production. The bad

news - with global climate change, the gyre-related

low productivity zones are growing in size.

Strangely enough, the lack of producers in the gyre has benefited humans in at least one aspect. The chlorophyll of the producers changes the color of the ocean, and this affects the trapping of heat and the wind currents. With a loss of living things in the North pacific gyre, a 2010 study states that typhoon formation has decreased in this region by more than 70%............Don’t get too excited, global surveying also says that the biological deserts of the gyres are growing much faster than global warming models would predict. As they grow, global productivity will be reduced, and that can’t be good for any of us.

We don’t make things any easier by letting chemicals run into the oceans either. Man made dead zones from increased nitrogen and phosphorous. These nutrients are needed for growing phytoplankton, but you can have too much of a good thing. The overgrowth of phytoplankton and algae in these areas, along with the decomposers they support, deplete O₂. The result is that there is no oxygen left for succession organisms, so larger animals cannot live there (neither can the plankton or algae after a while).

Man made dead zones correspond to areas of

runoff from sprayed fields. For instance, the estuary

of the Mississippi River in the Gulf of Mexico forms

the second largest man made dead zone in the world

each summer. Not to be outdone, the Baltic Sea dead

zone in Northern Europe is the largest, and it is

present all year round.

So the gyres are “almost dead” zones, and some polluted estuaries are considered dead zones. What about a body of water with dead in its name, the Dead Sea? At 423 meters (1388 feet) below sea level, the Dead Sea is officially the lowest body of water on Earth. Water flows into it, but not out of it, so all the salts and minerals just accumulate.

The temperature of the desert surrounding the Dead Sea is warm enough that evaporation plays a factor in increasing the salinity and mineral content of the remaining water. Only certain types of bacteria and algae can survive in the 33.7% saline waters (~8.6 x the salinity of the Mediterranean Sea).

Dunaliella salina algae are particularly abundant in the Dead Sea after the rainy season. These green algae produce antioxidant carotenoids to protect themselves from the intense sun exposure of the Jordan Rift Valley as well as huge amounts of glycerol (a three carbon carbohydrate) to counteract the osmotic pressure which would otherwise move all the freshwater out of the algal cells.

The algae is a good food source for halophilic (salt-loving) bacteria. However, during dry years, both the alga and bacteria are present in much lower numbers. But isn’t just the high salt that prevents larger plants and animals from living in the Dead Sea. The minerals that accumulate, such as magnesium chloride, calcium chloride, magnesium bromide, and calcium sulfate, are toxic to animals that drink the water. Fish from the freshwater feeders of the Dead Sea sometimes swim into the mineral-laden waters and are killed almost instantly.

The Dead Sea has receded a mile in the past twenty

years, and environmentalists warn it could be

completely gone by 2050. As it recedes, it leaves

salt on the rocks after the water evaporates.

The exception to this is the recently discovered freshwater springs that also feed the Dead Sea. Along the sea bottom near these vents lives a multitude of Archaea (often called extremophiles) that used to be classified as bacteria, but are now known to be a different kingdom of life. Spreading along the seafloor, mats of Archaea form biofilms, previously unknown in the Dead Sea.

The Great Salt Lake in Utah is similar to the Dead Sea biologically, but the lower salinity (some places are 5% salt, while others are 25 %; a railroad causeway has separated it into a more saline north arm and less saline south arm) allows more types of organisms to thrive in the water. Still no fish, but more types of algae, as well as some brine shrimp and brine flies.

Surprisingly, there is abundant flora and fauna around both the Great Salt Lake and the Dead Sea. The Jordan Rift Valley boasts camels, leopards, and ibexes, as well as fig trees and the rose of Jericho. In the western hemisphere, the Great Salt Lake has millions of shore birds, mostly fed by the 100 billion brine flies that hatch each summer. It is just the exception that here you have to move away from the water to find the life.

The above two examples indicate areas that have a lot of water, but too much salt for it to be useful. There is another place on Earth that has plenty of H₂O, but not enough liquid water to support much life – does that make sense?

Antarctica. It is hard to believe that with all that ice, miles thick in some places, there is not enough free water to keep plants and animals alive, but in many parts of the continent, that is the case.

McMurdo Station is the largest community on

Antarctica, if you don’t count the penguins. It is

located near the McMurdo Dry Valleys, the driest

places on Earth. This is due to the katabatic winds.

Cold air is more dense, and is pulled downhill. The

wind can reach speeds of 200 mph, and as it warms,

it evaporates all the moisture on the ground and in the air.

Some areas of Antarctica do support a little life; two vascular plants exist on the frozen continent, hair grass (Deschampsia antarctica) and the pearlwort (Colobanthus quitensis). These plants only grow on the west coast peninsula.

In the McMurdo Dry Valleys, east of McMurdo Station and the Ross ice sheet, almost nothing grows. There are hypersaline lakes here that put the Dead Sea to shame, including the Don Juan Pond that is 18x the salinity of the ocean.

There are no vertebrate animals in the valleys; microbes make up all the biology there. In all of Antarctica, only 67 species of insect are found, and most of these live as parasites on penguins.

The exception is the wingless midge (Belgica antarctica). At an average of 6 mm long, this fly is the largest purely terrestrial and year-round animal on the entire continent (penguins only live on the continent for part of the year). This flightless fly relative lives in algae mats, on rocks, and in the mud… just about anywhere it wants to. There are no competitors on Antarctica; this walking fly reigns supreme!

Belagica is well adapted to life in Antarctica. It is

black to absorb heat, and it is wingless so it won’t

be blown out to sea by the strong winds. It has a

short egg laying time and adult life span so that it

can complete its life cycle in the highly variable

summer season.

Other adaptations allow B. antarctica to thrive in this harsh environment. While the vast majority of plants and animals die with a relatively low level of dehydration (5-25%), these midges can survive a 70% water loss event - I suspect they can’t expectorate! In the winter…… WINTER? Isn’t it always winter there? Well, no; there is a colder season....the midge can react to winter by dehydrating and then coming back to life in the spring. Something like having a piece of beef jerky moo after you start salivating on it. Amazing.

The dry valley temperatures (-10˚C to -51˚C) could easily cause havoc with the midge’s protein function. Heat shock proteins help to stabilize protein function in temperature extremes, usually they are expressed (transcribed from DNA and translated from mRNA) for short periods of time, only when there is an abnormal event. But Belgica’s heat shock proteins are expressed all the time. This is a huge energy investment, and an investment that few animals are willing to make. But in areas with too much salt or too little water, sacrifices must be made.

Next time we will talk about one of the greatest exceptions in biology, an organism that can live in the Atacama Desert, the Jordan Rift Valley, the Great Salt Lake, and even at Antarctica. It's not a bacteria, not a fungus, not a plant, not an animal – this is one heck of an exception.

For more information or classroom activities on biological deserts, life in the Dead Sea, and life on Antarctica, see:

Biological deserts and gyres –

http://oceanservice.noaa.gov/facts/deadzone.html

http://news.sciencemag.org/sciencenow/2008/01/25-01.html

http://www.coas.oregonstate.edu/index.cfm?fuseaction=content.display&pageID=589

http://oceanmotion.org/html/background/wind-driven-surface.htm

http://marinedebris.noaa.gov/info/patch.html

http://www.wiserearth.org/article/bea19ef898eca1e2c820690bf8d22640

http://www.sciencedaily.com/releases/2011/02/110208142041.htm

http://disc.sci.gsfc.nasa.gov/oceancolor/additional/science-focus/ocean-color/dead_zones.shtml

http://serc.carleton.edu/microbelife/topics/deadzone/index.html

http://www.msnbc.msn.com/id/4624359/ns/us_news-environment/t/dead-zones-counted-oceans/

http://news.nationalgeographic.com/news/2010/02/100305-baltic-sea-algae-dead-zones-water/

http://www.livescience.com/15341-dead-zone-gulf-mexico-hypoxia-floodsdead-zone-gulf-mexico-hypoxia-floods.html

http://www.ewg.org/reports/deadzone

http://www.physorg.com/news199376811.html

Life around the Dead Sea –

http://news.nationalgeographic.com/news/2011/09/110928-new-life-dead-sea-bacteria-underwater-craters-science/

http://www.sciencedaily.com/releases/2011/09/110921120331.htm

http://adsabs.harvard.edu/abs/1998SPIE.3441...44O

http://www.wysinfo.com/Dead_Sea/dead_sea_flora.htm

Life in Antarctica -

http://library.thinkquest.org/26442/html/life/

http://www.marinebio.net/marinescience/04benthon/AAlife.htm

http://www.coolantarctica.com/Antarctica%20fact%20file/antarctica_animal.htm

http://schaechter.asmblog.org/schaechter/2010/01/cr.html

http://soundwaves.usgs.gov/2004/04/fieldwork.html

http://www.mobio.com/pages/wiw-antarctica.html

http://www.mcmurdodryvalleys.aq/activities/directory/11-2F12-Science/11-2F12-Biology-and-ecology

I Am Your Density

2012-02-15T07:00:00.000-05:00

Biology concepts – density of water, latent heat, stratification

Ernest Rutherford showed that atoms were

mostly space by shooting alpha particles at

a sheet of gold foil. Only a few particles struck

something solid, most just passed straight

through – because the atom is mostly the

absence of matter.

It is amazing to know that atoms are mostly empty space. Atoms make up everything around us, including the stuff that hurts when it hits me in the head, but even those things are mostly empty space... or maybe its my head that's empty.

When atoms fit together to form molecules and molecules fit together to form solids and liquids there is also space. How massive the molecules are and how much space is between them determines a substance’s density.

Density (mass per unit volume) has a big impact on biology, and we have been talking about water for a few weeks, so let’s talk about the density of water. Simply put, without water’s unique density properties, life as we know it on Earth would not be possible.

Pure liquid water has a density of 1 g/cm³ (or 1 g/ml). This is 800x times the density of air, so moving around in water is much harder and requires more energy than moving around on a land. Try running in the pool – we just aren’t built for moving in water.

Gram for gram, fish have more muscle than

any other vertebrate animal. Notice how the

muscle fibers are arranged in different

directions to provide forward movement as

the skeleton changes orientation.

But fish have adapted streamlined shapes and big muscles in order to move through water a little easier. The skeleton of a fish is the most complex of all vertebrates. The skull anchors the waving of the vertebral column and the attached muscles. The muscle fibers (myomeres) are arranged so that the muscles can contract in several different directions as the swaying motion passes down the fish body. In all, a fish is about 80% muscle. If you are a marine fish, you’d better be even stronger, since ocean water is slightly more dense (between 1.02 and 1.03 g/cm³, depending on the salinity).

But here is the amazing part - when water freezes, its density goes down. Most substances are denser as solids than as liquids, but water is the exception. As ice crystals form, the water molecules arrange themselves in a very particular order, and this order places slightly more space between them as compared to when they are in liquid form. More space means less mass per unit volume, ie. lower density (0.92 g/ml)….. and this is a key to life on Earth.

Water will form ice crystals in a definite structure,

with more space between the molecules than when

in liquid form. Snow crystals form from water vapor,

not liquid water, and retain a more hexagonal lattice

shape that may stack on one another.

Imagine for a moment that ice was denser than water. Then as the winter came, the winds would blow, the surface water in the pond behind your house would start to cool down, but the deeper water would be a little warmer (remember that water has a high specific heat, it likes to retain its heat. As the surface water arranged itself into a crystal form, ie. turned to ice, it would sink. The warmer water would then be pushed up higher and exposed to the colder temperatures, freeze, and fall to the bottom. Eventually the pond would fill with ice, and be completely frozen.

Few animals or plants could survive in a solid block of ice, so life would cease to exist in the pond. What is more, when spring came, the sun’s energy and warmer temperatures would have to penetrate to bottom of the pond in order to melt all the ice, and this would take longer than a spring summer and fall to occur. Most bodies of water would stay somewhat frozen all year long.

Our food webs (who eats who) depend so much on the growth in water, and half of the Earth’s oxygen’s production oxygen depends so much on phytoplankton, the one celled plants that float on the water’s surface and release oxygen as a by product of photosynthesis. So we couldn't survive for long with completely frozen bodies of water. What is more, frozen lakes and bays would eliminate huge heat sinks that normally keep the surface of the earth warm, so we would plunge into another ice age.

Can you imagine if the massive number of aquatic organisms died as a result of their environment being frozen year round? The animals that feed on them would then die, and the animals that feed on them would die, etc. Eventually the animals on the land that feed on the amphibians and fish would die, and so on. What’s more, we humans would be looking for more warm clothing while we gasped for enough oxygen to survive! Relax, we are all just fine, and it is because ice floats. Surface water freezes, trapping heat below and keeping the aquatic organisms comfy and cozy until spring.

The North American wood frog can freeze

solid in a long Arctic winter, but once it thaws,

it has work to do. It must find a find a mate and

then fertilize the eggs. The fertilized eggs have

to develop from to tadpoles and then to adults

during the short warm period. Then they can

freeze next winter.

You might have noticed that above I mentioned that MOST organisms can’t survive being frozen, but there is an exception. The wood frog (Rana sylvatica) winters in shallow burrows that are not protected from the cold. To survive, the frog actually freezes solid!

Nucleating proteins in the frog’s blood act as point for ice to form as soon as the frost touches the amphibian’s porous skin. Since the frog is still above 0˚C at this point, the freezing is slower, and the frog can control it. As the liquids freeze, the water is pulled out of the frog’s cells. It replaces the water with glucose and sugar alcohols, that keep the cells from forming ice crystals (they are sharp and would puncture the cells causing permanent damage and death). Eventually, the frog is 65% frozen and the internal organs are surrounded by a pool of ice until spring, when it takes about 10 hours for the frog to thaw and hop away. Scientists are now using this process to freeze and thaw rat hearts and livers without damage, in hopes to use to the process in human organs for transplant.

So the wood frog takes advantage of freezing in order to survive. Humans can also take advantage of freezing water (other than keeping your drink cold); in fact, your orange juice may depend on it. Freezing of oranges or grapes ruins them for the same reason it kills animals, it causes frostbite. Ice crystals stab through the cell membrane and cell contents spill out. This isn’t conducive to continued function.

To prevent oranges and grapes from freezing, farmers will spray them with water when their frost warning systems sound the alarm. Does that make sense, spraying with water to keep something from freezing? It has to do with a property of freezing called latent heat. This is an amount of energy taken up or given off when a substance changes phase (solid to liquid to gas). The energy goes to changing the arrangement of molecules with no change in temperature.

Oranges can be protected from freezing by

spraying them with water which then freezes!

In a controversial use of genetic modification,

bacteria that do not permit ice crystal formation

can be sprayed on the oranges to compete with

the normal bacteria there. These "ice-minus"

Pseudomonas syringae can reduce frost damage

on oranges, but have not been used commercially.

As water surrounding the orange or grape changes from liquid to solid, the formation of crystals gives off heat (539.4 gram-calories per gram of water frozen). The latent heat of the freezing mist is enough to keep the fruit above 0˚C. This technique doesn’t work if the temperature falls much below 0˚C or stays at 0˚C for an extended time, but it does work well enough to save millions of dollars per year in freezing damage.

Thermal changes have more to do with differences in water density than salt concentration does, so seasonal changes can alter density in both freshwater and salt water. Even if the changes are not enough to form ice or boil the water, differences in temperature can result in different layers of water within a freshwater body or an ocean.

Both salt water and freshwater are affected by the sunlight that strikes their surfaces. As water warms, it’s density decreases, and the nutrients in the water stay close to the surface. This supplies phytoplankton and algae with lots of food, and blooms can occur.

As winter approaches, the surface water cools and becomes more dense (down to 4˚C). The dense water drops to the bottom and taking nutrients down to the benthic organisms. When all the water reaches 4˚C, the surface can begin to freeze.

In the spring, the process is reversed, and the temperature layers (stratification) can churn again. In salt water, the differences in salinity are added to the differences in density to bring complex stratifications, both in salt content and temperature.

Stratification shows how temperature can set up

layers of water of different density (least dense is

the epilimnion). In the winter, the water is churned,

and then churned again in spring. These churnings

based on changing density move the nutrients around

so everyone gets fed.

Different organisms thrive in different temperature and salinity layers. In order to stay put, some floating organisms (planktonic) and swimming organisms (nektonic) can adjust their buoyancies. Fish can use swim bladders, which are air filled cavities to help them stay buoyant. The size of the bladder is regulated by the CO₂ and O₂ in the blood that can remain dissolved or leave the blood as a gas.

Bladderwort plants also use air filled cavities to keep part of themselves afloat. Sharks, on the other hand, produce large amounts of oil in their livers to reduce their density; oil is less dense than water, just look at your salad dressing layers.

Plankton can also slightly adjust their densities, but floating is easier for very small things. To them, water is thick, the polar charges have a larger effect on their small bodies. It would be like us trying to swim in molasses. They still have to adapt to seasonal changes in density, but they do it in more subtle (and harder to explain) ways.

Just because there is water around, it doesn’t mean that life will be easy. Next week we will look at a continent-sized exception to idea of water availability.

For more information, classroom activities and laboratories on the density of water, latent heat, North American wood frog, or stratification, see:

Density of water –

http://www.elmhurst.edu/~chm/vchembook/122Adensityice.html

http://aquarius.nasa.gov/seawater_mix_sink.html

http://www.cleanet.org/clean/community/activities/oceans.html

www.uas.alaska.edu/attac/ampdf/activity3.pdf\

latent heat –

http://www.splung.com/content/sid/6/page/latentheat

http://www.ucblueash.edu/koehler/biophys/8c.html

http://www.3dplumbing.net/ontplumbing/latent_heat.htm

www.cbu.edu/~jholmes/P201/Part42.ppt

http://apollo.lsc.vsc.edu/classes/met130/notes/chapter2/lat_heat2.html

http://www.hk-phy.org/contextual/heat/cha/act_boiler_lf_e.html

North American wood frog –

http://www.fcps.edu/islandcreekes/ecology/wood_frog.htm

http://www.dnr.state.mn.us/reptiles_amphibians/frogs_toads/truefrogs/wood.html

http://www.units.muohio.edu/CRYOLAB/projects/woodfrogfreezing.htm

http://www.naturenorth.com/winter/frozen/frozen3.html

http://www.pbs.org/wgbh/nova/nature/costanzo-cryobiology.html

http://news.nationalgeographic.com/news/2007/02/070220-frog-antifreeze.html

stratification –

http://www.waterontheweb.org/under/lakeecology/05_stratification.html

http://www.maine.gov/doc/nrimc/mgs/education/lessons/act37.htm

http://www.windows2universe.org/php/teacher_resources/activity.php

http://pubs.acs.org/doi/abs/10.1021/ed081p1312A

www.schoolship.org/files/inlandseas/649.pdf

http://www.ehow.com/how_7374642_create-stratified-water-graduated-cylinder.html

http://centerforoceansolutions.org/climate/impacts/ocean-warming/water-column-stratafi/

http://faculty.gvsu.edu/videticp/stratification.htm

http://eesc.columbia.edu/courses/ees/climate/lectures/o_strat.html

http://www.lmvp.org/Waterline/spring2002/stratification.htm

Do You Drink Like A Fish?

2012-02-08T07:37:00.000-05:00

Biology concepts – fish osmoregulation, shark osmoregulation, semelparity, iteroparity

The irony of fish drinking is not lost on this café in

the Hotel Portofino at Universal Orlando. What I

really like is the eye patch.

You’d think that fish would never be thirsty; if he needs a drink, he just opens his mouth. But some fish don’t drink a drop! Wouldn’t that be similar to some birds never breathing? Ridiculous.

Fish are good examples of the problems of maintaining proper water and salt concentrations. Some fish live in freshwater, and some in saltwater. These are opposite sides of the same coin when dealing with osmoregulation.

Freshwater fish live in a hypotonic (low salt) environment. The flesh of the fish contains more salt than does the water. Diffusion and osmosis work to equalize salt concentrations in different compartments. Therefore, water will move from the lake or river into the fish’s tissues in order to balance the salt concentrations by osmosis. Salt will not move out of the tissues, since there are molecular mechanisms that work to keep the inside.

Like the kangaroo rat, freshwater fish don’t drink. They do take in water when they eat and move water across their gills, but they don’t take in water just for the water. Even without drinking specifically, freshwater fish take in way more water than they need. Anywhere freshwater contacts a fish cell, water will move inward; this includes the gills, the mouth and gut, and the skin.

In a situation like this, kidney-mediated concentration of urine would be counterproductive; why retain water when water is exactly what you have too much of? Therefore, freshwater fish excrete large amounts of urine. Their kidneys have large glomeruli, which move lots of water into the collecting tubules for excretion.

Saltwater and freshwater fish have different ways of

dealing with salt and water loss and conservation.

Freshwater fish must conserve salt, while saltwater

fish must conserve water. The kidneys play a role,

but so do the chloride cells in the gills.

But if the freshwater fish aren’t drinking, how do they get their salt, which is present in low concentrations in the water? You’d think they would have to be drinking all the time just to collect enough salt. To get around this, they conserve the salt they ingest through the food they eat. They also take in salts through their gill chloride cells, actively pumping sodium and chloride out of the freshwater and into cells that have a lot of mitochondria (to provide energy to pump the salts). The relatively short collecting tubules of the freshwater fish kidney allow for reuptake of a lot of salt, while excluding almost all the water.

Marine (saltwater) fish have the opposite problem. Their tissues are of much lower salt than they surrounding hypertonic ocean, so osmosis wants to dry them out, sending water out of their bodies. The amount of available drinking water is extremely low - can you imagine dying of dehydration while surrounded by water. Just ask anyone who has survived a shipwreck and prolonged float in the ocean; drinking seawater can be lethal.

However, marine fish must drink all the time in order to keep enough water in their body. Retaining water would be an essential function of marine fish kidneys. They are all fish, but their kidneys work in exactly opposite ways. Marine kidneys have small or absent glomeruli, so little water is taken out of the blood, but long collecting tubules in order to excrete as much salt as possible.

Drinking a lot of saltwater leaves marine fish with way too much salt; more than their kidneys can get rid of. To aid in salt excretion, they also have chloride cells in their gills. In the opposite fashion of the specialized gill cells of freshwater fish, the chloride cells of saltwater fish actively sequester salts from the blood, and then pump the sodium and chloride out into the seawater.

Sharks have unique ways of maintaining

salt and water. I have no idea of their

mechanisms for pepper regulation.

But sharks are an exception among marine fish. They have a different way to combat high salt concentrations. Remember that osmosis means that water moves from areas of low solute (high water concentration) to areas of high solute (lower water concentration). For many marine fish, this would mean a constant loss of body water to the ocean and quick death by dehydration; much like pouring salt on a slug.

To overcome this movement, sharks produce and retain a huge amount of a chemical called urea; it is one of the soluble wastes that animals normally get rid of. This molecule doesn’t affect the electrical potential that salts create, but increases the solute concentration in the shark’s tissues at levels higher than in the seawater, so water (without the salt) will diffuse into the shark’s body. This is its source of fresh water.

Therefore, sharks are osmoconformers; they maintain an osmotic balance with their environment. If the shark becomes too salty and salt needs to be excreted, it has a salt gland, much like that of birds and reptiles, but the shark’s gland is located in it anus, not near its eyes or nose – that’s a big difference! Taken together, there is no force for movement of water in or out of the shark’s tissues, and the shark remains shark-shaped instead of shriveling or swelling up.

Here is a bullshark caught in the Potomac River.

And you thought that sharks in Washington D.C.

were just in the federal buildings.

An exception to this rule for sharks is the bull shark; it can live in both saltwater and freshwater. Most sharks put into in freshwater would absorb too much water and die of water toxicity. However, the bull shark’s kidneys can adjust to the salinity of the water within a short period of time. Their kidneys will remove less salt and more urea from their blood and tissues and into their urine. They move from being osmoconformers to osmoregulators.

A shark that can live in freshwater; this can present a real problem. There have been many bull shark attacks in rivers and estuaries (video), where people don’t expect to encounter sharks. It is suggested that this behavior and physiology is an adaptation that gives the bull shark a protected nursery for their young, away from predators.

Most fish are stenohaline (Greek, steno = narrow and haline = salt), which means they are restricted to either salt or fresh water and cannot survive in water with a different salt concentration than to that which they are adapted. However, there are exceptions- like the bull shark mentioned just a second ago.

Some salmon species are born in freshwater, then move to saltwater for several years, and then return to freshwater to spawn. Other fish, like some eels, are born in a marine environment, move to freshwater, and then go back out to sea to reproduce. If freshwater and saltwater fish kidneys work opposite of one another, how can there be fish that can do both?

Salmon returning upstream to spawn have many obstacles

to overcome. Their spawning grounds are usually a thousand

feet or more above sea level so they must leap up many

waterfalls. Oh, there are hungry bears too.

Salmon are famous for migrating to and from the sea. Almost all the species are semelparous (in Latin, semel = once and parous = breeding); this means that they return to their freshwater streams to spawn only once, and the trip and the reproduction kills them. The one exception is the Atlantic Salmon (Salmo salar). This species is spawned in, and returns to, the calm streams along the Atlantic coast several times in its life to spawn. This reproductive strategy is call iteroparity (itero = repeated). Iteroparous species lay fewer eggs at a time, the advantage is that survival chance is increased by repeated spawning – one bad year doesn’t destroy a big proportion of the population.

The migratory species of salmon are osmoregulators, as are most freshwater fish; their physiology demands a certain salinity level, and use energy to produce that level in their tissues. However, they can also adapt to various salinity levels. As such, these salmon as well as bull sharks are known as euryhaline (eu = good, haline = salt). Their physiology changes with the salt concentration.

While in freshwater the salmon will not drink, and will produce copious amounts of urine to get rid of the excess water it absorbs through osmosis. But when it migrates to the ocean, it drinks all the time, and its kidneys work hard to remove the excess salts.

Chloride cells in euryhaline fish can sequester or

excrete salt, based on the hormone signals they receive.

This helps some fish move from aquatic to marine

environments and back again.

But the gills are the key to survival in the both the freshwater and saltwater environments. Energy consuming reactions will transport both Na⁺ and Cl^- against their gradients, so they pump Na⁺ and Cl^- into the fish’s tissues in freshwater and out of the fish’s tissues in saltwater. It is an adaptation of the marine fish’s chloride cells to work in both directions. This switch, as well as the kidney’s change in urine concentration, takes time. Therefore, salmon will spend days or weeks in intermediate zones, or estuaries, before going out to the ocean, and before returning to the rivers.

These are difficult lifestyle choices for salmon, the trips and the spawning kills them. So what is the advantage? The movement to oceans provides the growing salmon with readily available sources of food, so competition is reduced. The return to where they were spawned is just a good bet; if the stream was good enough to spawn them, then it is still probably a good place to lay eggs. Finally, working so hard to get to the spawning ground just a single time allows for selection of strong individuals, allows for huge numbers of eggs to be laid (the chance that some survive goes up), and the death and decomposition of the adults provides nutrients for the hatched fry (baby salmon). But these are human interpretations, I bet there are other advantages and disadvantages. However, one thing is for sure, the balance sheet for these species comes out in favor of these adaptations – if it did not, nature would adapt further.

The eggs that don’t hatch and the carcasses of the mated

Adults create nutrient rich waters for the fry to develop in

before they head out to sea.

How about one more exception for today? Some individuals in semelparous species of salmon (Chinook, Coho, Pink, Steelhead, etc.) will not die after spawning, and will return again to the ocean. These individuals are often females, and are often smaller than average. These gals reverse their salt and water conservation strategies several times in their lives, making them prize winners for osmoregulatory exceptionality.

Next week, let’s tackle how the properties of hard water affect all life on Earth.

For more information and classroom activities on osmoregulation in fish and sharks, chloride cells, and reproduction strategies, see:

Osmoregulation in fish –

http://www.angelsplus.com/ArticleOsmosis.htm

http://www.ca.uky.edu/wkrec/RedDrumPhysiology.htm

http://www.raingarden.us/osmoregulation.htm

http://www.drjohnson.com/expanded/water/osmoregulation.html

http://www.marietta.edu/~mcshaffd/aquatic/sextant/excrete.htm

http://marinediscovery.arizona.edu/lessonsS01/blennies/2.html

www.omsi.edu/sites/all/FTP/Files/.../NH.../NH-C1-BendCarrot.pdf

Chloride cells –

http://www.bio.umass.edu/biology/mccormick/Cl_cell.html

http://www.fishmartinc.com/hc-osmoregulation.htm

www.cnr.uidaho.edu/fish511/Readings/Gill%20morphology.pdf

Osmoregulation in sharks –

http://www.sharks.org.za/osmoregulation.html

http://www.sharksavers.org/en/education/shark-biology-behavior/385-how-bull-sharks-can-live-in-fresh-water-through-clever-osmoregulation.html

http://meganbioblog.blogspot.com/2010/11/osmoregulation-in-sharks.html

http://www.sharksavers.org/en/education/shark-biology-behavior/395-differences-between-sharks-and-bony-fish-more-than-just-the-skeleton.html

http://users.tamuk.edu/kfjab02/Biology/Vertebrate%20Zoology/b3405_ch04.htm

semelparity and iteroparity –

http://www.nature.com/scitable/knowledge/library/semelparity-and-iteroparity-13260334

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=15&ved=0CE4QFjAEOAo&url=http%3A%2F%2Fib.berkeley.edu%2Flabs%2Fslatkin%2Feriq%2Fclasses%2Fbiol472%2Flectnotes%2Flect7_15.pdf&ei=yRMsT7zxB8GQsALxhPitDg&usg=AFQjCNG8SK-33EBWcuipxsTSnty9JEP9hw

http://dictionary.sensagent.com/semelparity+and+iteroparity/en-en/

www.csun.edu/~msteele/classes/Ich530/lectures/14_reproduction.pdf

http://web2.uwindsor.ca/courses/biology/weis/55-324/lecture9.htm

Don’t Eat The Yellow Snow

2012-02-01T08:00:00.061-05:00

Biology concepts – osmoregulation, tonicity, phytohormones, avian kidney, pinnieds, cetaceans

African elephants are larger than asian elephants, but their

urine production is similar. A 2007 study found that

African elephants can differentiate family members

based on their urine. It is similar to marking territory,

but they use urine to keep track of family members who

may be out of sight.

The asian elephant can urinate as much as 55 liters/day. That's about 3/4 of the volume of the average size bathtub! By comparison, the vaunted racehorse can only manage about 6 liters/day. Maybe we should rethink that old saying.

We know from the posts of the last few weeks that both salts and water are necessary for life, and that they work together to keep their concentrations within safe limits; a process called osmoregulation. You suspect correctly that kidneys and urination is involved, but what about plants – they don’t use the restroom.

For many animals, the kidney is the major organ of osmoregulation. The average adult human voids 1-2 liters of urine each day, but an uncontrolled diabetic with polyuria (poly=much and uria=urine) might expel 5-6 liters. Maybe we should bet on diabetics at the racetrack.

We get rid of water and soluble wastes via our kidneys. The kidneys filter the blood; nearly 800 liters of the red stuff each day. The basic filtering unit of the kidney is the nephron, who we met previously (Sorry, I Don’t Drink), made up of the Bowman’s capsule and sets of tubules.

Solutions of different tonicity have similar effects on plant

and animal cells, but plant cells can handle it better because

they have a rigid cell wall.

If the body is low on water, more water is reabsorbed in the tubules. Likewise, if the body has too much salt, few of the salt ions are reabsorbed in the tubules. In this way, our kidneys are basically concentrating our wastes in a small amount of water for excretion from the body. The amount of water depends on many factors, including the need to keep the cells at the right level of tonicity (concentration of salt relative to outside the cells).

Solutions can be hypertonic, meaning they have more salt than the cytoplasm, and water will flow out of cells by osmosis. Solutions can also be hypotonic, with less salt than in the cells (water will flow in to the cells) or isotonic, with the same osmotic pressure inside the cells as outside.

We all know that we don’t urinate the same amount all the time – drink more, go more. However, you don’t urinate the same amount you drink; your urine is concentrated by your kidneys in order to conserve water. Therefore, there must be some control mechanism. The answer is hormones. A hormone (“to set in motion” in Greek) is a small protein that is released from one cell and then acts as a chemical signal on other cells, either through the bloodstream (endocrine hormones) or through a duct (exocrine hormones) to the bloodstream or directly to other cells.

The angiotensin system. 1. The body senses that water

is low. 2. The kidney releases renin. 3. Renin and

angiotensin converting enzyme produce angiotensin II

from angiotensin I in the lung. 4. Angiotensin II stimulates

aldosterone in the adrenal glands. 5. Aldosterone causes

more water and salt to be reabsorbed in the Loop of Henle;

this increases the blood volume and solves the problem.

Aldosterone is produced by the adrenal glands and acts on the distal collecting tubules of the kidneys. This endocrine hormone acts to conserve sodium and water and secrete postassium, thereby reducing urine volume but increasing the loss of potassium. Aldosterone is released in response to angiotensin levels in the plasma, which in turn are controlled by sodium and water levels in the blood.

Arginine vasopressin (AVP, also called antidiuretic hormone) is another endocrine hormone that reduces the amount of water to be lost in the urine. This hormone is produced in the pituitary gland of the brain and also works to conserve water. By reducing the amount of water lost, the blood volume (which is mostly water) is increased, so blood pressure increases. This is why people are given intravenous fluids when they have lost a lot of blood.

The exceptions to this mechanism of kidney function are the mammals that live in hypertonic (saltwater) environments, like whales and dolphins (cetaceans) and seals or walruses (pinnipeds, latin for feather- or fin-footed). It is hard to study the urination in these animals in their native environment; they urinate in the ocean. Are you going to measure their individual contribution to the ocean – I think not.

Water wants to flow out of the cells and into the sea (hypertonic as compared to the cells), trying to balance the salt concentrations in both places. Therefore, the marine mammals must conserve freshwater or they become dehydrated. Both pinnipeds and cetaceans have large kidneys with enough renal tubule length to produce very concentrated urine, thereby conserving water. However, it appears cetaceans don’t really take advantage of this. Instead, they make a lot of metabolic water (Gimme Some Dihydromonoxide) and can keep from dehydrating by using the water they produce through cellular respiration.

Here is an inside view of a seal kidney. It’s huge! The many

lobules provides much tubular area to take up freshwater

and concentrate the urine.

Pinnipeds don’t drink water saltwater to any degree at all, they get their freshwater from their diet and their metabolic water. Scientists use to think this was also true for cetaceans, but recent studies show that they do drink a small bit of seawater – not enough meet their water needs, but also not more than their kidney’s can handle.

Don’t think that marine (saltwater) mammals have it so bad. If they were to abandon the seas for freshwater sources, they would just trade one problem for another. Freshwater mammals have too much of a good thing, they run the risk of losing too much salt by being in so much salt poor (hypotonic) water all the time. This is why the kidney is so amazing, it can adapt functionally and anatomically to get rid of too much water or too much salt, depending on where you are. That is not to say the kidney is the only anatomic mechanism needed to maintain osmolarity within a tight range. Many organisms need more than kidneys, and have developed completely different mechanisms of osmoregulation.

Bird kidneys may be small, but they represent an evolutionary

intermediate, Some parts have short loops, like most mammals,

and some have long loops, like pinnipeds and cetaceans. However,

most of the kidney has reptile-like nephrons with long loops.

Birds share some water conserving and salt regulating apparatus with mammals. Avian (bird) kidneys have about 75% of their nephrons with reptilian structure, and 25% mammalian nephrons, containing a Loop of Henle. Therefore, avian kidneys are not as good at removing water and regulating salts as mammals are. Mammal urine can be concentrated 20-50x as compared to blood (the Kangaroo rat can produce a 9000x concentration), but birds can only manifest about a 2-3 fold concentration.

Therefore, birds have another mechanism to get rid of salt and maintain an osmotic potential within its limits. The salt gland is found in birds and reptiles. In many birds it is located near the eyes or nostrils (in crocodiles, salt is excreted through their tongues – everything tastes salty to them). The salt gland removes Na⁺ and K⁺ from the blood, allowing birds and reptiles to consume saltwater or animals that live in saltwater.

Some organisms have it easier, like amphibians. With semi-permeable skin, they just leak salt out through their entire skin surface. Other organisms aren’t so lucky, like plants.

Plants must also regulate salt concentration, but they don’t have a familiar excretory system; in fact, they don’t have a specific osmoregulatory system. Water is lost via transpiration (Sorry, I Don’t Drink), and adjustments can be made to alter the amount of evaporation that occurs. Unfortunately, transpiration of water is linked to moving nutrients such as salts up the plant from the roots to the leaves. Therefore, shutting down transpiration will also shut down movement of nutrients.

Plants in high temperature, low humidity, high wind environments have the highest rates of transpiration and are in danger of losing too much water. Once again, hormones are the answer. Plants do have hormones (phytohormones), so they probably have to deal with teenager issues just like human parents. Abscisic acid is an important hormone which shuts off transpiration. This phytohormone closes the stomata (stoma = mouth in Greek) on the upper sides of leaves, from which water evaporates and gases are exchanged. Abscisic acid also promotes water absorption from roots and root growth.

Some plants are cryptophytes by surviving unfavorable

seasons either underground (geophytes), hide their

seeds in the marshy mud (helophytes) or underwater

(hydrophytes). Hydrophytes in general are plants that

have their roots in water or water-logged soil.

Many xerophytes (plants that live in hot, dry places) have adapted to resolve these issues. They have leaf modifications to reduce water loss; needle-shaped leaves, sunken stomata, and waxy cuticles to cover the leaves. On the other hand, in hydrophytes (plants that live completely or almost completely in water), salts and water can be absorbed in the entire plant, not just the roots.

In terms of cations (Na⁺, K⁺), plants have a problem. They use potassium as their primary intracellular cation, but dirt is usually potassium-poor. Therefore, plants have K⁺ transporters to actively take up this ion. Unfortunately, the transporters don’t discriminate very well between K⁺ and Na⁺, so often times too much Na⁺ is taken up into plants.

Red mangroves have impermeable roots that help keep

out salt, and can also secrete some salt from there leaves,

but their most visible mechanism is the yellow salt leaves.

Excess Na+ can be toxic to cells, so measures must be taken to deal with these ions. Glycophytes are plants that are salt-sensitive, and include many of the plants that we cultivate. Therefore, soil salinity is an important factor in agriculture and gardening. Much research and breeding continues to an effort to produce crops that are better at differentiating uptake of K⁺ and Na⁺. Halophytes (halo=salt, phyte=loving), on the other hand, will allow the uptake of the excess ions, and then sequester them in vacuoles to prevent cellular damage.

Some plants live in extremely high salt environments. One example, the red mangrove tree, is a facultative halophyte. Facultative is a fancy way of saying “optionally.” These trees live in estuaries, where the river meets the sea. The water is quite salty there, and the mangroves are rooted in the water, so excess salt could be a problem. To deal with the toxicity of the excess Na⁺, the mangrove will store the salts in selected leaves, called the “kidney leaves.” When a toxic level is reached, the leaves turn yellow and just drop off. The tree must constantly invest energy in producing new leaves, so there is a cost to this way of life, but it seems to work for them.

If plants that live in or near seawater have adaptive mechanisms to maintain proper salt concentrations, then how about fish? We'll look at the osmoregulatory tricks by these organisms next week.

For more information, classroom activities or laboratories about osmoregulation, tonicity, abscisic acid, avian kidney, pinnipeds, cetaceans, see:

Osmoregulation –

http://www.biology-online.org/dictionary/Osmoregulation

http://www2.uic.edu/~bcatal1/bios/bios245/learn/osmoregulation.pdf

http://people.eku.edu/ritchisong/bird_excretion.htm

http://staff.jccc.net/pdecell/cells/paramicium.html

http://5e.plantphys.net/article.php?ch=3&id=268

http://www.mhhe.com/biosci/genbio/espv2/data/animals/009/index.html

http://www.zoology.ubc.ca/courses/bio332/Labs/OSMO.HTM

http://leavingbio.net/OSMOSIS%20AND%20DIFFUSION.htm

tonicity and osmotic pressure –

http://chemistry.about.com/b/2010/11/09/osmotic-pressure-and-tonicity.htm

http://www.biotech.ufl.edu/EM/data/osmos.html

http://www.biologyjunction.com/tonicity%20animations.htm

http://sciencefair.math.iit.edu/projects/tonicity/

http://www.biology-online.org/biology-forum/about21154.html

abscisic acid –

http://www.plant-hormones.info/abscisicacid.htm

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ABA.html

http://www.plantcell.org/site/teachingtools/TTPB12.xhtml

http://www.pearsonhighered.com/mathews/ch23/abscisic.htm

http://www.ncbi.nlm.nih.gov/pubmed/11726706

http://5e.plantphys.net/article.php?ch=3&id=268

http://abscissic.blogspot.com/2011/01/abscissic-acid-as-homeostatic-hormonal.html

www.vitis-vea.de/admin/volltext/e034916.pdf

avian kidney –

http://people.eku.edu/ritchisong/bird_excretion.htm

http://www.2ndchance.info/gout.htm

http://www.ima.umn.edu/biology/wkshp_abstracts/layton1.html

http://www.holisticbirds.com/pages/urinarysystem0503.htm

http://en.wikipedia.org/wiki/Salt_gland

pinnipeds –

http://www.nmfs.noaa.gov/pr/species/mammals/pinnipeds/

http://www.marinemammalcenter.org/education/marine-mammal-information/pinnipeds/

http://marinelife.about.com/od/marinelife101/f/pinniped.htm

http://www.sfgate.com/getoutside/pinnipeds.html

www.farallones.org/documents/pinniped_fs.pdf

http://www.cyhaus.com/marine/pinnipeds.htm

http://www.whaletimes.org/TenThingsPinnipeds.htm

http://what-when-how.com/marine-mammals/pinniped-physiology-marine-mammals/

cetaceans –

http://www.ucmp.berkeley.edu/mammal/cetacea/cetacean.html

http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/

http://www.acsonline.org/factpack/index.html

http://www1.pacific.edu/~e-buhals/cetacean.htm

http://www.learner.org/jnorth/www/jntalk/0068.html

http://what-when-how.com/marine-mammals/osmoregulation-marine-mammals/

Keeping Your “Ion” The Ball – Salts and Life

2012-01-25T08:00:00.047-05:00

Biology concepts – salts in biology, osmotic potential, action potential, transpiration

Dietary salt – crucial for survival;

Veruca Salt – not so much.

In Latin, verruca means wart, so Roald

Dahl was probably trying to tell us something

when he wrote her character into Charlie

and the Chocolate Factory.

We have learned that one of the crucial functions of water in living organisms is to help regulate the salt concentration in and between the cells (Gimme Some Dihydromonoxide). But why do living things require salts? We all know that we must have a source of salt (sal in Latin) in our diet or we die; the Romans gave it so much importance that part of a soldiers pay was to be used specifically for buying salt – his salary. But what are its functions?

Water tends to flow from where salts are in low concentration (high water concentration) to where salts are high concentration (low water concentration). Just like other molecules, water diffuses to where its concentration is lower (It’s All In The Numbers-Sizes in Nature). Osmosis (osmo = push in Greek) is the special name given to the diffusion of water, for every other molecule it is just called diffusion.

Too much salt is destructive to cells and organisms, so water helps control the salt held in the body. On the other hand, too much water is also bad for living things (water toxicity), so salts help to control the water concentration. Together, this ratio of salt and water inside and outside of the cell leads to a controlled imbalance called the osmotic potential of the cell. Every living thing has systems to maintain this osmotic potential within a small range (osmoregulation, we will discuss this in more detail soon).

The osmotic potential is measured in units

of pressure (bars). It is equal to the amount

of water that will move in response to a

difference in solute concentration across

a membrane.

When in water, sodium chloride (NaCl, table salt) dissociates into Na⁺ and Cl^- ions, and it is these ions, along with K⁺ (potassium ion from KCl) that perform many functions in living organisms. Sodium is 10x more concentrated outside the cell, while potassium is 20x more concentrated inside. The slight difference in the charges of the two ions (and the fact that most Cl^- is outside cells) sets up a membrane potential in cells.

An important function of this membrane potential is in the neuron (nerve cell), as rapid reversal of the potential along the cell membrane (through ion specific channels) produces an electrical current that we know as the action potential (neural impulse). It is the rapid change in concentrations of Na⁺ and K⁺ cations (positively charged ions) inside and outside of the neurons that sends the messages from our muscles to our brains and back, as well as all the thought processes in our brain.

The action potential of the neuron is not simple.

Sodium is higher outside and potassium is higher inside.

When a signal is received (usually from another neuron),

sodium leaks in and potassium leaks out. The slight

difference in the the charge of each means that the neuron

goes from -70 mV to +40 mV. This depolarization travels

down the neuron’s membrane for the entire cell.

Salt's importance is illustrated when their concentrations get out of whack. Too little salt produces symptoms similar to dehydration, with cramping, nausea and confusion. Too much salt results in hallucinations and insanity. The classic example of too much salt intake is being lost at sea. Not having a supply of freshwater, people may start to drink seawater. The salt concentration is too high; their kidneys can’t get rid of all the excess, and the action potentials in the brain begin to misfire. People will see things that aren’t there, and will make critically bad decisions. Many end up swimming away from relative safety and subsequently drown.

We can get rid of some salt through our skin. Is your dog is happy to see you when licking your face after you arrive home, or does he just want the salt? Athletes will often eat bananas to augment their potassium stores and keep the cramps away after exercising. They should really follow that run with a bowl of lima beans; they have much more potassium.

However, munching on black licorice is alot like running a long distance. Glycyrrhizin is the main glycoside (a sugar bound to a non-carbohydrate) in licorice root and is 20x sweeter than sucrose. Glycyrrhizin prevents potassium reuptake in the kidney, so you end up urinating out most of your potassium stores. You could cramp up due to excessive snacking.

Na⁺ and K⁺ work in muscle function; cramping and paralysis may result from too little or too much salt. Your heart is a muscle, so changes in salt concentration in the cell can cause heart attacks as well. Many a mystery movie has included the injection of potassium chloride to induce a heart attack. Sodium and potassium cations help maintain proper blood pressure, proper acid/base levels, and proper movement of carbon dioxide from the blood to the lungs. There are precious few functions in which these positive ions don’t play a role.

Collagen and elastin help to make your skin and

joints pliable. O.K., maybe not this elastic – this is

the result of Ehlers-Danlos syndrome, which is

often a genetic disease.

When we think of salt, we usually think of table salt (NaCl), but there are more functions for K⁺ than there are for Na⁺, and it is present in higher concentrations in the cell. Potassium is important for the formation and crosslinking of collagen and elastin proteins. These connective tissue proteins hold all your tissues together; they keep your skin from tearing when someone pokes you in the arm, and allow your lungs to expand without ripping when you inhale. So K⁺ is pretty important even when not working with Na⁺. It is interesting then that potassium is the only major mineral nutrient for which there is not a recommended daily allowance.

Remember that we often take in these salts as NaCl or KCl. Does the Cl^- play a role in organism function? – you bet it does. Chloride anion (a negatively charged ion) is used to produce the hydrochloric acid (HCl) that breaks down the food in our stomachs. Chloride also works in the immune system, hypochlorite (the same active molecule as in bleach) in the white blood cells helps to kill infectious agents and activates other immune system molecules. Chloride is required for the uptake of vitamin B12 and iron and helps control your blood pressure; therefore, Cl^- isn’t just that other ion that comes in with Na⁺ or K⁺ (or Ca²⁺).

Chloride ion is elemental chlorine that has gained one electron. This doesn’t seem like much of a change, but it is the difference between life and death. Chlorine itself is a yellowish green gas and it can kill you in a matter of seconds. Chlorine really wants that extra electron, and it doesn’t care if it has to rip it from your lung proteins to get it. When you breathe in chlorine, it reacts with the water in your lungs to produce hydrochloric acid that eats away the cells. It will also react with almost any carbon-containing molecule and further destroy the lung tissue. It was suggested during the American Civil War that chlorine gas could be useful, but it wasn’t until World War I that it was used as a weapon.

Chlorine is poisonous, but we use it to disinfect drinking water and pools. When diluted greatly in water, chlorine does not have the strongly deleterious effect on our cells as it does as a gas, but can still react with and kill microorganisms. Chlorination of water began in the Chicago stockyards around 1908, when the decaying meat and gut bacteria were getting into the drinking water and making the residents sick. The bleach used to disinfect surfaces is much the same as the chlorine used to disinfect 75% of the drinking water in the U.S.; it’s just there in lower concentration. Now chlorine is used in pools as well, and you know it is working because your eyes get red and sting.

Did you know that plants had openings in their leaves called

stomata? Turgor pressure caused by the flow ions in and

out of the guard cells makes the stomata open or close. Their

shape changes based on the amount of water in the guard cell.

There are no exceptions to the rules of salt requirements (weird, isn’t it). All living things need to take in Na⁺, K⁺, Ca²⁺, and even Cl^-. Plants use potassium and sodium for water balance, especially to bring morphologic changes like the blooming of flowers. These cations, along with chloride, work in the opening and closing of pores in the leaves (stomata) for the uptake of carbon dioxide and the release of oxygen and water during transpiration (Gimme Some Dihydromonoxide), and in the chemical splitting of water during photosynthesis. It seems that other organisms rely on these ions even more than animals.

All bacteria require potassium and sodium for osmotic regulation and cellular activities. As the concentration of Na⁺ in a bacteria’s environment goes up, its dependence on Cl^- becomes greater. Fungi, protists, and even viruses depend on salts to remain alive, even though viruses are technically not a form of life. Viruses carry nucleic acid, and salts are needed to balance the charges of the DNA or RNA so it can be stuffed into the viral package, a function within the area of molecular biology.

Giardia lamblia and other protozoa use salt ions

to control their osmotic potentials and for other

biochemical functions. Giardia can also change

your potassium levels by causing intense diarrhea

after drinking contaminated stream water.

Molecular biology involves replication of DNA, the transcription of DNA to RNA, and the activities of RNA translation to proteins. K⁺, Cl^-, and Na⁺ are involved in all these areas. In a feedback mechanism, salt ions control the switches that turn on genes that then control the levels of the ions. If one ion is too high, it will turn on the genes that code for proteins which remove that ion from the cell. Isn’t evolution nifty?

Tightly regulating salt concentration in the cell is important for life, and we have to drink water (kangaroo rats excepted) in order to stay alive. These are the peanut butter and jelly of biology and we will start to see how they work together next time.

For more information and classroom activities on salts in biology, osmotic potential, action potentials, or chloride ion in biology, see:

Salts in biology –

http://www.ext.colostate.edu/pubs/foodnut/09355.html

http://www.physiologymodels.info/contractile/NaK_pump.htm

http://muscle.ucsd.edu/musintro/ecc.shtml

http://www.webelements.com/sodium/biology.html

http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01140.html

http://www.youtube.com/watch?v=ntlX5Ve6yj8

http://en.wikipedia.org/wiki/Sodium_in_biology

http://en.wikipedia.org/wiki/Potassium_in_biology

http://www.webelements.com/potassium/biology.html

Osmotic potential –

http://physioweb.uvm.edu/diffusion/pages/OsmPotential.htm

http://h2g2.com/dna/h2g2/A686766

www.mrothery.co.uk/studentswork/.../osmosis%20presentation.ppt

http://biology.clemson.edu/bpc/bp/Lab/110/osmosis.htm

http://biology.kenyon.edu/HHMI/Biol113/movemet%20of%20water%20in%20plants.htm

http://5e.plantphys.net/article.php?ch=3&id=29

Action potential –

http://students.cis.uab.edu/nkm188/project_back2.html

http://faculty.washington.edu/chudler/ap.html

http://outreach.mcb.harvard.edu/animations/actionpotential.swf

http://bcs.whfreeman.com/thelifewire/content/chp44/4402002.html

http://www.mun.ca/biology/desmid/brian/BIOL2060/BIOL2060-13/CB13.html

http://www.blackwellpublishing.com/matthews/channel.html

http://teach.genetics.utah.edu/content/

http://faculty.washington.edu/chudler/chmodel.html

http://science.education.nih.gov/supplements/nih2/addiction/guide/lesson3-1.htm

http://www.accessexcellence.org/MTC/96PT/Share/conley.php

http://www.ywpw.com/cai/software/hhsimu/

Chloride in biology -

http://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v03/030731r00.HTM

http://muscle.ucsd.edu/musintro/ecc.shtml

http://www.comprehensivephysiology.com/WileyCDA/CompPhysArticle/refId-cp080117.html

http://www.bio.umass.edu/biology/mccormick/Cl_cell.html

http://www.webmd.com/a-to-z-guides/chloride-cl

http://ivy_league0.tripod.com/rhyme_of_the_ancient_wanderer/id101.html

http://labtestsonline.org/understanding/analytes/chloride/tab/test

http://www.livestrong.com/article/277296-sodium-potassium-chloride-in-the-body/

stomata –

http://faculty.washington.edu/ktorii/stomata.html

http://bioweb.usu.edu/kmott/Complexity_Web_Page/Stomata.htm

http://evolution.berkeley.edu/evolibrary/article/mcelwain_03

http://www.geocraft.com/WVFossils/stomata.html

http://www.nature.com/scitable/topicpage/plant-vacuoles-and-the-regulation-of-stomatal-14163334

http://www.biologycorner.com/worksheets/stomata.html

http://www.biologyjunction.com/leaf_stomata_lab.htm

http://uwstudentweb.uwyo.edu/d/dbrouss1/stomate.htm

http://www.biologycorner.com/worksheets/stomata.html

http://www.classtech2000.com/toucan/modules/stomata/stomata.htm

http://www.accessexcellence.org/AE/AEC/AEF/1994/case_leaf.php

http://www.apsnet.org/edcenter/intropp/topics/Pages/OverviewOfPlantDiseases.aspx

Sorry, I Don’t Drink

2012-01-18T08:00:00.136-05:00

Biology concepts – water conservation, kidney function, metabolic water, adaptation, water uptake

“Koala” in aborigine means “no drink.” The

moist eucalyptus leaves are poisonous
to most animals, but koalas have a special
bacteria that can break down the toxic

eucalyptus oil.

We all know we need water to survive (see Gimme Some Dihydromonoxide), so why is it that koala bears have decided they don’t need to drink?

Koalas eat eucalyptus leaves, as well as mistletoe and a few other leaves. The leaves contain a good amount of water, and the koalas can survive on just this source of moisture. It also helps that they sleep about 18 hours each day, have a very slow metabolism, and feed about 80% of the time they are awake - it is apparent that they have evolved into teenagers. This doesn’t mean that koalas can’t or don’t drink, they just don’t require drinking to get their daily requirement of water unless a drought dries up the leaves.

However, there exist species that never drink. The kangaroo rat and the spinifex hopping mouse take temperance to the extreme. These rodents can live out their entire life (5-7 years) and never use the water fountain. They have chosen their lifestyles wisely, considering that the hopping mouse lives in the Australian outback and the kangaroo rat lives in Death Valley! We will use the kangaroo rat as our exemplar for this exception.

Unlike the koala that gets its water from its diet, the kangaroo rat eats seeds- not a great source of water. Therefore, it must have other strategies for survival. Foremost, it has developed ways to prevent water loss. Its kidneys super-distill its urine so it is up to 17 times more concentrated than its blood; the best we can do is 3-4 times concentration.

Please meet the nephron. The blood vessels form a

glomerulus, which is surrounded by the Bowman’s capsule.

Notice how the blood vessels surround the Loop of

Henle to take the retained water and salts back into

the blood.

The kidney is made up of thousands of filtering units called nephrons (Greek nephros = kidney). Each nephron has a Bowman’s capsule that filters the blood of waste,and removes some of the water and salt. The filtrate then flows through a series of tubules that adjust the concentration of the salts and water according to what the body needs to retain or dispose of at that particular moment. The portion of the kidney that removes water from the urine back to the blood are called the Loop of Henle, and these loops are much longer in the kangaroo rat’s kidney as compared to those in human kidneys. Therefore, more water is returned to the blood and the urine wastes are more concentrated.

The kangaroo rat doesn’t look thirsty,
even though it doesn’t look like his
burrow has seen water for years.
I would imagine that despite the hot
weather and the fur coat, kangaroo
rats don’t sweat; they can’t afford the
water loss.

The kangaroo rat doesn't stop there. He burrows deep and keeps his burrow small. This helps to trap and moisture that escapes via his exhalations. If you breathe on a mirror, it will show condensation; you invest a lot of water in keeping your lungs moist and functional. The rat can reabsorb some of the moisture present in its burrow via its skin, respiratory tract, and his seeds.

The dry seeds that the kangaroo rat finds are stored in a pouch in its mouth and taken back to the burrow. Here they are stored for several days in a corner, during which time they also absorb moisture from the burrow’s air. This is just another way the rat recycles some of its own moisture.

Finally, the kangaroo rat makes the most of the water it produces. Yes, it generates water – but so do you. Think of the production of ATP (aerobic respiration) as the opposite of photosynthesis. In the building of carbohydrates (during photosynthesis). In photosynthesis, water is split and the hydrogen is added to the growing carbohydrate. But in the electron transport chain for oxidative phosphorylation (making ATP) oxygen accepts an electron and then reacts with hydrogen to form water. Water made this way is called metabolic water. In humans, metabolic processes like generation of ATP produce about 2.5 liters of water each day. In the kangaroo rat, this process is more efficient and the water produced is kept in house.

As the electrons from the breakdown of glucose travel down the

electron transport chain in the mitochondrial membrane, they

help to move protons (H+) out. As they leak back in through the

ATPase, they help make ATP. The electron needs some place to go,

and an oxygen atom is a good place to go. This makes
the oxygen reactive; it picks up hydrogens to form water.

Add all these measures up and the kangaroo rat changes its habitat from Death Valley to Life Valley. Unfortunately, not many other organisms can join it there.

Just because it doesn't drink or eat watery foods doesn’t necessarily mean that an organism doesn’t take in water. Amphibians absorb environmental (air or surface) water through their skin. Frogs are a group of amphibians that can be used as good examples. Frog skin is smooth, without hair or feathers, and is permeable to water. A ventral patch (sometimes called a seat patch) of skin is located on the underside of the frog between its two hind legs. This skin patch has a higher concentration of blood vessels just beneath the surface, ready to suck available water into the bloodstream.

To get to the blood vessels below the skin, the water passes through a series of aquaporin (aqua = water, pore = opening) protein channels in the skin cells. These proteins also control water entry into bacteria; they are evolutionarily very old and therefore must be important. The frog splays its legs and lays down on a surface that is moist from dew or rain, and the water flows through the ventral patch aquaporins and into the bloodstream. Interestingly, water doesn’t flow the other direction, although some water does evaporate through amphibian skin. That is why frogs must live close to water. Toad skin is much less likely to lose water, so they can live farther from water.

Some plants also garner water in unconventional ways. Non-vascular plants (mosses, lichens, liverworts, hornworts) as well as many epiphytes (bromeliads, orchids, some ferns and mosses, mistletoe) are plants without roots. However, a lack of roots or vessels doesn’t stop these plants, they have evolved marvelous adaptations to procure the water they must have.

Non vascular plants are just that – plants without vascular tissues (xylem and phloem). Plant vascular tissues are tubes inside the stem that transport water (phloem) and sugars (xylem) throughout the plant. Non-vascular plants don’t have roots and vessels to absorb and transport water and minerals, although mosses and ferns may have rhizoids that serve that purpose. In general, non-vascular plants grow close to water so that they can use all their structures to absorb water by capillary action as well as by absorbing water directly from the air.

Epiphytes are even better at pulling water from the air, although they still use pooled rainwater as well. This group of plants may have dense root systems, but some are not anchored in the ground to give support to the plant. Instead, many of them use other plants for support. Orchids are particularly good at storing water in their thick stems and absorbing water through their exposed roots. Velamen (latin for veil or cover) layer root cells of orchids are adapted to prevent water loss while a few cells in this layer and the layer below are hollow and allow water to pass through.

Bromeliad epiphytes are better at absorbing pooled water and humidity through their leaves than in taking water in through their roots. In tropical regions, they have two adaptations to aid this process. One, many bromeliads have near vertical leaves shaped to trap water at their bases (together called a tank) that may hold over a liter of water. Second, they have specialized cells at the base of the leaves to transfer this water (and minerals) to the interior of the plant. The most economically important of this Bromelioideae subfamily is the pineapple, which is a terrestrial bromeliad. It can absorb water through its roots in the ground, but if you are growing one, try to keep the tank from drying out as well.

The top picture is looking down on a bromeliad trichome.
The middle picture is looking from the side. See how they
curl up to allow water in. When they fill with water,
they fold down (lowest picture), to prevent water loss
from the cells underneath.

Bromeliads living in areas with less rain, such as Spanish moss, have a different adaptation. Their leaves store the water that is absorbed through specialized structures called trichomes on the surface of each leaf. Trichomes have shields made of non-living cells, much like our outer layers of skin. Other cells form a disc and are mostly a void, capable of rapidly taking in water. When these cells swell, their tips curl downward (remember turgor pressure from Plants That Don’t Sleep Well).

Curling forms a small cavity under the disc that draws water in to the protected foot cells under the disc by capillary action. These cells also have aquaporin proteins that draw the water into the interior tissues. When there is less water around, the disc cells flatten out and cover the stalk cells, preventing water loss. The whole structure acts like an anti-umbrella!

So organisms can get water from air, food, or metabolism - but we can go them one better. There is an animal that doesn’t eat or drink during its entire adult life, can you imagine? O.K. – so its life is only five minutes long, but it doesn’t eat or drink during that five minutes.

Adult female sand burrowing mayflies (Dolania Americana) emerge from their water-borne larval form and seek two things, a male for mating, and a place to deposit her eggs. Since all larvae are evolved to mature at once, males are around in large numbers; problem 1 solved. And since they live near water, place to lay eggs are also plentiful; problem 2 solved. Within five minutes, her work is done and she dies – not a glamorous life.

The American sand burrowing mayfly lives a year or more

as a larvae in the water, but when it metamorphoses into

the sexually mature form and leaves the water, 5 minutes

is all she gets. There may be species with shorter sexual

reproductive life span, but it would be hard to spot, and

harder to study.

Different species of mayfly live varying amounts of time – some live as adults for up to 2 days - oldtimers! But even if the mayfly wanted to invest some of their precious time in eating and drinking, they couldn’t do it. Adult mayfly mouthparts are vestigial (having become nonfunctional through evolution) and their digestive systems disappear as they mature. So in this biological case, a lack of form follows a lack of function.

There is another crucial element of life that interacts with water, and ocean going organisms are intimately familiar with it. Salt is just as important for life as is water, but why? We will begin looking into the functions of salts and how they interact with water next time.

For more information, classroom activities, and laboratories about water uptake, renal function, trichome, or mayflies:

Animals that don’t drink –

http://library.thinkquest.org/3500/polarbear.htm

http://www.kidcyber.com.au/topics/koalas.htm

http://www.veganpeace.com/animal_facts/Frogs.htm

http://www.desertmuseum.org/kids/oz/long-fact-sheets/krat.php

http://www.alicespringsdesertpark.com.au/kids/nature/mammals/mouse.shtml

Kidneys –

http://www.youtube.com/watch?v=7nesHuVEe8M&feature=related

http://www.comprehensive-kidney-facts.com/kidney-anatomy.html

http://www.youtube.com/watch?v=aQZaNXNroVY

http://www.khanacademy.org/video/the-kidney-and-nephron?playlist=Biology

http://oracle3927.tripod.com/nephron.htm

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CEAQFjAD&url=http%3A%2F%2Fwww.apsarchive.org%2Fdownload.cfm%3FsubmissionID%3D1785&ei=7-oST7rJL-qvsQL9q8CKBA&usg=AFQjCNGprOyj9oVkDNKowpCPpxK2D3HgUw

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CD8QFjAC&url=http%3A%2F%2Flifesciences.envmed.rochester.edu%2Fcurriculum%2FSEPAClass%2F3.TEACHERKidneyDialysis7-23-09.pdf&ei=0OsST_DVL4STgwfJ_sS-BA&usg=AFQjCNFweWcQcIeROvktESpk7DoA_Jzu0Q

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CEcQFjAD&url=http%3A%2F%2Flifesciences.envmed.rochester.edu%2Fcurriculum%2FSEPAClass%2F2.STUDENTKidneyProblem7-23-09.pdf&ei=0OsST_DVL4STgwfJ_sS-BA&usg=AFQjCNFl-pKLn0G3-5Rmuky8CTrrJP43Ng

http://www.pbs.org/wgbh/nova/teachers/resources/subj_05_03.html

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&ved=0CHgQFjAJ&url=http%3A%2F%2Fwww.apsarchive.org%2Fdownload.cfm%3FsubmissionID%3D1785&ei=0OsST_DVL4STgwfJ_sS-BA&usg=AFQjCNGprOyj9oVkDNKowpCPpxK2D3HgUw

Aquaporins –

http://www.ks.uiuc.edu/Research/aquaporins/

http://www.vivo.colostate.edu/hbooks/molecules/aquaporins.html

http://www.aquaporins.org/

http://www.ncbi.nlm.nih.gov/pubmed/11773613

http://scifair.org/news/chemistry-news/one-protein-two-channels-scientists-explain-mechanism-in-aquaporins.html

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CC4QFjAA&url=http%3A%2F%2Fwww.apsarchive.org%2Fdownload.cfm%3FsubmissionID%3D1912&ei=Wu0ST4TNKo7iggeYg6zMAw&usg=AFQjCNFxPFXm3XwoxYOlJB-lPX-oxAPJ_Q

Trichomes –

http://www.420magazine.com/forums/how-grow-marijuana/71982-what-trichomes-trichome-101-a.html

http://www.astrographics.com/GalleryPrintsIndex/GP2023.html

http://www.sbs.utexas.edu/mauseth/weblab/webchap9secretory/9.4-1.htm

http://bromeliads.gardenwebs.net/trichomes.htm

http://www.bsi.org/brom_info/what.html

http://plantsinaction.science.uq.edu.au/edition1/?q=content/15-4-3-epiphytes

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0CFMQFjAE&url=http%3A%2F%2Fcsusciencemethods.wikispaces.com%2Ffile%2Fview%2FFast_Plants_unit_LP&ei=r_AST_nvO8qrsAKp0dXcAw&usg=AFQjCNEIHT9dlpgkKb53N0BUbBCOyTsyLA

Mayflies -

http://insects.tamu.edu/fieldguide/aimg3.html

http://www.entm.purdue.edu/mayfly/

http://www.cirrusimage.com/ephemeroptera_mayflies.htm

http://www.ucmp.berkeley.edu/arthropoda/uniramia/ephemeroptera.html

http://www.mayflyintheclassroom.org/

http://www.rectory-farm.org.uk/HTML_Files/Mayfly_Classroom.html

http://www.learnnc.org/lp/editions/mudcreek/6603

http://biofreshblog.com/2011/05/17/mayfly-in-the-classroom/

http://dnr.wi.gov/org/land/er/biodiversity/index.asp?mode=info&Grp=18&SpecCode=IIEPH02010

Gimme Some Dihydromonoxide

2012-01-11T08:00:00.052-05:00

Birds need water just like the rest of us,

but beaks make it harder. They may suck

it up like a straw or scoop it up like a bucket,

or by leaning back and letting the rain fall in.

At some point or another we've all said, “I’m about to die of thirst.” Of course we can only survive for a few short days without water, but do you know why?

Cells are full of salt water (saline), but are also crowded with proteins, carbohydrates and lipids (saline + organic molecules = cytoplasm). This suggests the importance of H₂O, but it doesn’t say anything about the reasons behind its importance.

Water is the solvent (the liquid part of a solution), while the proteins and carbohydrates are the solutes (the solids dissolved in the solvent). Lipids (a type of fat) are insoluble in water; therefore, they are good for building cell membranes. They help keep what is in in, and what is out out. With a lipid membrane, our cytoplasm doesn't leak out on to the floor.

Cytoplasm isn’t water plus some organelles. As shown in

this electron micrograph, it is more like a gel, packed

with organelles, proteins, minerals, sugars, and nucleic

acids. There is water, but just enough to separate the other

constituents. Photomicrograph credit: Dr. Jeremy Burgess/Science

Photo Library.

The intracellular solutes are surrounded by water. It’s like the green jello with pineapple that your Aunt brought every Christmas, except that it's packed to the gills with pineapple. Cytoplasm is more crowded than the public pool on a 104˚F day when the ice cream vendors have gone on strike. In some cases, there may only be a few molecules of water separating different cellular components, but this water layer is crucial.

Water is the solvent in which most cellular reactions take place. Water is made up of an acid (H⁺) and a base (hydroxyl, OH^-). Together, they are two hydrogen atoms and one oxygen, H₂O! Having the H⁺ around keeps the bases in check, while the OH^- keeps the acids in check. This helps keep the cytoplasmic pH within a small range (buffers it), about 7.35-7.45. Buffering the cytoplasm ensures that that reactions proceed in the proper direction and at the proper rate.

Water transports materials within the cell, from cell to cell, and through the blood and lymph. The partial negative and positive charges, the high surface tension, and the cohesive properties of water make it good at its jobs.

Water being sucked up in a capillary tube

uses cohesion (water sticking to water) and

adhesion (water sticking to the glass tube).

Water likes to bond to itself (cohesion) via hydrogen bonds formed between the positive H⁺’s of one water molecule and the negative OH^-‘s of two others. Cohesion is what makes water form drops as it rains, and what gives water its strong surface tension. Surface tension is why some insects can land on water and take off again. Water striders (family Gerridae), walk on water and you can actually see the depression in the surface, like when you stand on your bed. They are helped out in this endeavor by hydrophobic (water-fearing) tiny hairs on their legs and feet.

Water also likes to hydrogen bond other surfaces; this is called adhesion. If you pour water into a small diameter glass, you can see it cling to the side (meniscus, Greek for crescent), and even seem to rise up the side of the glass (see the image above). If the glass tube is narrow enough, like in a capillary tube, the water will climb up the tube against gravity. The force that drives this is adhesion.

Water striders spread their weight over a large area to

reduce their pressure on the water. They are also helped

by the hydrophobic proteins on their legs. But mostly, the cohesive

force of the water raises the surface tension so the strider

remains on the surface.

The adhesive force is driven by the bipolar (a negative end and a positive end) nature of water, just as with cohesion. The positive H⁺ is attracted to any negative molecules, and the negative OH^- is attracted to anything positive. Together, they are attracted to most everything, not just other water molecules.

Hydrogen bonding and the adhesion and cohesion they produce are important for plants. How does water absorbed by a redwood’s roots get to its leaves way up high? The mechanism has several features, the most important of which is suction. When water in the leaves evaporates, it creates negative pressure that actually pulls the water up from the roots through the plants vessels.

The negative pressure alone isn’t strong enough to keep the water moving against gravity, but when you add in the cohesion of water molecules to one another, and adhesion of the water molecules to the sides of the vessels, it all works out. The sum total of these actions is called transpiration, and is responsible for moving water against gravity in plants.

Water also participates in many cellular reactions, most famously photosynthesis. During the Calvin cycle of photosynthesis (dark reactions) glucose is produced, water is split into hydrogen atoms that are incorporated into the growing carbohydrate and gaseous oxygen (O₂) that is released. It is this transformation of water to gas that drives transpiration. In cellular respiration, when carbohydrates are used to produce chemical energy (ATP), the exact opposite occurs – water is formed from oxygen and hydrogen.

Other cellular reactions, such as the hydrolysis (hydro = water and lyse = split) of fats or proteins are occurring inside cells all the time. In these types of reactions, a water molecule is split into H and OH while the target molecule is also split in two; one part gains a hydrogen and the other gains a hydroxyl group. This is crucial for the normal degradation of cellular proteins by protease enzymes, amongst other things.

If that wasn’t enough, water acts as temperature buffer, helping organisms hold a more constant temperature. Water does not warm up fast and it does not cool down fast; it tends to keep an even temperature. It has a high specific heat (1 calorie/gram C˚), meaning that you must add a lot of energy in order to change its temperature. Water’s high specific heat evens out temperature fluctuations in the body and allows reactions to proceed in a controlled fashion.

Finally, many organisms use water pressure to hold their form, an example of the turgor pressure we learned about several weeks ago (Plants That Don’t Get A Good Night’s Sleep). For instance, you return home from a trip to find your plants have turned brown and are drooping in their pots. Your goldfish are belly up, and the expensive six-pack in your fridge is now a two pack – the neighbor you asked to look after them did a bang up job. If you’re lucky, the plants stand back up a few hours after a good soaking, especially if you fertilize them with your goldfish carcasses. Your plants need the water for everything we have discussed, but also because the water pressure in the cells keeps them the plant stem and leaves standing rigid.

The tube feet of starfish and other eichinoderms have a

suction cup on the end of the podia. The internal portion

is the ampulla, the tube that holds water to regulate the

tube movement.

In a similar fashion, starfish store and move water through a series of hollow tubes to form a hydrostatic skeleton. In the general sense, this type of skeleton is any fluid filled cavity surrounded by muscle, in which the actions of the muscles work against the fluid pressure in the cavity. Worms, and many other invertebrates have this type of support system.

But starfish take the concept a bit further. Not only is water used to maintain the form and structure of the animal; it makes up the water vascular system for locomotion (tube feet), food transport, and respiration. By moving water in and out of specific tubes in the different arms, the muscles contract and extend the tube feet, pushing them against a surface. The movement of water in and out of the tube feet is also the primary way to move oxygen into the tissues of the starfish, and the water pressure can be used to evert their stomach (it will protrude out their mouth and turn inside out) to surround and engulf food. Ugh!

We always knew water was crucial for life, and now we know why. Its importance is reinforced when you consider how much water there is in different organisms. Humans are about 60% water by mass, but it varies from person to person. Younger children are normally have a slightly higher percentage of water, maybe 70%, while morbidly obese people have much less water, remember that fat is stored in the absence of water (Is it Hot in Here or is it Just My Philodendron?).

The golden barrel cactus has ribs that can expand and

contract, depending on the hydration state of the plant.

It is also called a mother-in-law’s cushion….that’s just mean.

Plants require even more water. Cactuses can be more than 90% water after a good rainfall. The places where cacti grow have variable water availability, so when water is present, they must take advantage. The endangered golden barrel cactus has ribs that can expand to take in more water. In addition, the golden barrel cactus is round to reduce surface area and has a thick waxy surface, both of which reduce water loss.

Despite these dehydration prevention measures, cacti still lose water over time, and it might not be replaced for a long time. Therefore, cacti have evolved mechanisms to withstand the loss of almost 60% of their water without any negative ramifications. In this area, they are the exception. Typical flowers and trees can only withstand a 20% water loss without damage; however, this is still much better than humans can do.

No matter what your personal water percentage might be, you can only afford to lose about 5% of your water without suffering symptoms. At mild levels of dehydration (5%), you may feel groggy or get a headache. Higher levels of water loss will bring tingling in the muscles, nausea, and confusion. If the loss reaches 10-15%, there can be muscle spasms, delirium, and the kidneys may be permanently damaged (if water loss is held for a sufficient period). Held above 15%, dehydration is usually fatal. However, athletes can lose up to 30% of their body water in the short term, but it must be replenished immediately so that performance or normal function will not be compromised.

When we say normal function, we mean those functions of water we have mentioned, but also several others we haven’t. Water, along with surfactant proteins, works to keep our lungs absorbing oxygen. Water lubricates our joints and tissues to avoid friction damage. People with xerostomia (Greek, xero = dry and stoma = mouth) or xerophthalmia (dry eyes) use artificial saliva or tears to prevent damage to mucous membranes. Finally, water acts as a cushion, absorbing pressure and force to protect our organs from traumatic damage, like a punch to the gut.

Damage can come in many forms when water is low, so all living organisms require water intake to function and remain safe, right?……Or is just most organisms? Next time.

For more information, classroom activities, or laboratories about water in biology, the properties of water, transpiration, or the Calvin cycle, see:

Water in biology –

http://www.amnh.org/exhibitions/water/?section=lifeinwater&page=lifeinwater_f

http://www.everydayhealth.com/water-health/water-body-health.aspx

www.coastalcoolers.com/body.pdf

http://www.chemcraft.net/wbody.html

http://www.rawfoodexplained.com/water/waters-role-in-the-body.html

http://www.weightlossunit.com/Pages/Healthy_eating_articles/role_of_water_in_human_body.html

properties of water –

http://www.uni.edu/~iowawet/H2OProperties.html

http://faculty.rcoe.appstate.edu/goodmanjm/asuscienceed/background/waterdrops/waterdrops.html

http://hyperphysics.phy-astr.gsu.edu/hbase/surten.html

http://daphne.palomar.edu/jthorngren/water.htm

http://www.youtube.com/watch?v=LrNwcxMWJ68

http://www.physicalgeography.net/fundamentals/8a.html

http://propertiesofwater.org/

http://www.watereducation.utah.gov/WaterScience/Properties/default.asp

http://aquarius.nasa.gov/prop_fresh_sea.html

www.uas.alaska.edu/attac/ampdf/activity3.pd

www.edinformatics.com/math_science/water_ice.htm

transpiration –

http://ga.water.usgs.gov/edu/watercycletranspiration.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Transpiration.html

http://www.phschool.com/science/biology_place/labbench/lab9/intro.html

http://www.biologymad.com/resources/transpiration.swf

http://extension.oregonstate.edu/mg/botany/transpir.html

http://www.eoearth.org/article/Transpiration

http://www.youtube.com/watch?v=U4rzLhz4HHk

www.ucar.edu/learn/1_4_2_18t.htm

http://www.sciencebob.com/blog/?p=162

http://beckyboop.wordpress.com/2011/03/22/plant-transpiration-lesson-plan/

http://www.learnnc.org/lp/pages/3600

calvin cycle –

http://www.science.smith.edu/departments/Biology/Bio231/calvin.html

http://www.bio.umass.edu/biology/conn.river/calvin.html

http://highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter5/animation_quiz_1.html

http://www.youtube.com/watch?v=_NIhg1qa_L0

http://www.khanacademy.org/video/photosynthesis---calvin-cycle?playlist=Biology

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CalvinCycle.html

http://sites.bio.indiana.edu/~hangarterlab/courses/b373/lecturenotes/photosyn/carbon/c3.html

http://rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/dark.htm

http://www.johnkyrk.com/photosynthesisdark.html

http://www.educationalrap.com/song/photosynthesis.html

No Introductions Necessary?

2012-01-04T08:00:00.014-05:00

Biology concepts – introduced species, invasive species,

The United States is a melting pot, and it is one of our

greatest strengths. The questions is, is it also a good

idea for plants and animals?

The United States is an amazing place to live; nearly everyone’s family is from some place else. But if you ask the people you meet on any given day, they will likely say they are from the USA. Most have had time to assimilate and find their niche in their family’s adopted homeland. Can you name a place on Earth where this situation applies to its animals and plants?

If a place like this existed, it would probably be some place young. It would probably also be someplace isolated, where the exchange of species would not have been easy. Sounds like an island to me; probably a volcanic island(s), something like the big island of Hawaii, in a chain that is only 300,000 years old….. O.K., it is the big island of Hawaii.

Hawaii is the biggest and youngest of the Hawaiian Islands.

Formed from five active volcanoes, it is growing larger

everyday.

Since they are islands, it makes sense that many of Hawaii's species came from somewhere else. A key question is, how did they get there? If seeds were brought by migratory birds or washed up on shore, or if an animal wasn’t quite dead when a predatory bird dropped it on the island, that’s one thing. But if humans brought plants or animals and released them by accident or deliberately, that is something else.

History shows the latter mechanism has been responsible for most of the diversity in Hawaii. Estimates are that the rate of species introduction in Hawaii has outpaced the natural rate of diversification by 2 million times. Over half of the island’s plants species are there because of people, not nature.

Many of the plants and animals that have been brought to Hawaii were introduced deliberately, but that is not the definition of an introduced species. Whether an organism is imported and released to serve some specific purpose, or whether it is a stowaway on a ship or otherwise unknowingly allowed to get loose, it is an introduced species (also called neozoon, alien, exotic, non-indigenous, or non-native species). Introduced species are those plants and animals living outside their native range due to some human intervention, whether intentional or not. For Hawaii, this began in the 19^th century.

The Hawaiian monk seal is known as

Ilio‐holo‐i‐ka‐uaua in Hawaiian,

meaning, “the dog that runs in

rough waters.” They are critically

endangered, with only about 1100

remaining individuals.

Hawaii has only two native mammals, the Hawaiian monk seal (Monachus schauinslandi) and the Hawaiian hoary bat (Lasiurus cinereus semotus), and no native terrestrial (land) mammals. Many other mammals were introduced in the name of making money, like cattle and goats, while others were brought in specifically to make hunting more enjoyable.

In the last few posts, we have been discussing the activity patterns of different organisms, and we suggested that the organisms that interact most likely have the same or overlapping activity patterns. A tragic story illustrating this concept has played itself out in Hawaii since the late 1800’s.

Ladd & Company (from Maine) had established a lucrative sugar industry on the big island by 1834, and this increased the ship traffic in and out of Hawaii. The ships brought rats, an all too common introduced species.

In Jamaica, the problem of rats in the sugar cane fields was an old one. A successful sugar planter, W.B. Espeut, thought that introducing the Indian mongoose to the sugar cane fields could help with their rat problem. Apparently it did, and Espeut told everyone he could find. Subsequently, 72 mongooses were brought to the big island in 1883. There were some objections raised in the local papers, but as with most good ideas, they were roundly dismissed.

It is sad that mongooses

in Hawaii are causing damage, while

at the same time, mongooses are

endangered in their native India

due to habitat loss.

The problems became apparent not too long after mongoose introduction. In Jamaica there is a predator that eats mongooses, the fer-de-lance snake, but no such predator in Hawaii. What is the number one cause of death for mongooses in Hawaii? Old age!

No predator means unfettered reproduction, and female mongooses can have two litters each year. The result has been lots of mongooses, all looking for a meal and a mate.

Did all these Hawaiian mongooses do their job, did they get rid of the rats? Not really, and this is where a biology class could have helped. Mongooses are diurnal, they hunt during the day, but the rats on Hawaii are nocturnal. Oops. You would have thought someone might have noticed that beforehand.

I’m sure the odd mongoose runs into the odd rat as one goes to bed and the other begins its day, but that isn’t enough to force either species to adapt; everyone is happy keeping to his old schedule. Now Hawaii has too many rats and too many mongooses.

Mongooses (mongeese?) will eat almost anything (fruits, snails, mammals, insects, amphibians, lizards, spiders), but they really like bird eggs. Many species of bird in Hawaii, including the Nene (Hawaiian goose, the state bird) are on the brink of extinction because of the mongoose.

The story of the mongoose and the rat illustrates another point. Not only are there few mammals on Hawaii, there are even fewer native predators. As a result, many animals and plants that happen to be from Hawaii originally (or least for a long time) have adapted to this lack of predators by not developing defense mechanisms. This is an advantage, in that energy normally spent on defense can be saved for other metabolic or reproductive activities. Nature always wants to reroute energy if it is being used unnecessarily.

But, if predators are then introduced (and they were by the bucketful after Western Europeans and Americans became involved) the native animals are particularly at risk. The lack of native predators and the introduction of alien predators is illustrated by the case of the western yellow jacket. Though often mistaken for a bee, the yellow jacket is actually a wasp, and a nasty one at that.

Western yellow jackets have a smooth

stinger, so they can sting multiple

times. However, they rarely sting when

away from their nest.

The yellow jacket is an example of an accidentally introduced species, arriving in a shipment of Christmas trees. Law required that a percentage of the trees be shaken to knock off insects before shipment, but the required percentage of shaken trees was apparently too small, or the time shaken was too short, because it didn’t work.

In the continental U.S., the yellow jacket forms an annual nest and starts over building a colony each spring, but in the warmer climate of Hawaii, the species has become perennial, with nests as large as an SUV – more like a Lincoln Navigator, not the small Honda CR-V.

The yellow jacket is a carnivorous wasp only as a larva. The adults eat only nectar, but acquire meat to feed their young. This has decimated native Hawaii insect species, which in turn has reduced the amount of food available to bird species. In addition to insects, the wasps will devour dead birds and other large vertebrates, but will kill lizards and amphibians to feed their young.

In addition to accidentally introduced species, there are many feral (fera in Latin = wild beast) species on the big island. Feral species are animals that were domesticated, but have returned to the wild and propagated there. Their freedom could have come by accident or on purpose, as with cats and dogs in the cities. We call them strays, but they are correctly referred to as feral.

The stories of sewer alligators inspired sculptor

Tom Otterness to create a slightly scary piece in

bronze. It is located in a14^th Street subway station

in NYC.

All those alligators in the sewers of NYC aren’t feral, because they were never domesticated. And yes, alligators have been caught in the sewers of NYC; the latest Time and Post articles I could find were from August of 2010. They don’t live for years, grow to be monsters, or reproduce - but small ones, probably recently released, are found just about every year.

In most cases, feral animals cause problems and don’t offer many advantages. They can act as reservoirs of disease, compete with native species for resources, prey on indigenous species and eat native plants.

If there are benefits to feral animals, they will depend on your view of things. Some ranchers can make money by rounding up feral cattle or horses. Feral canines provide an income for the town dogcatcher. Stray cats can help keep the rodent population down; there seem to be many advocates for feral cats. There is even a website that advertises all the wonderful things about sterilized feral cats. Really? They want to catch them, sterilize them, and then release them again?

Literally, thousands of plants and animals of all kinds have been introduced to the big island, and now we get to the crux of the issue – introduced species that become invasive species, ie. those that do damage to the natural ecosystem by becoming dominant by killing or displacing native species. The question is – which is the exception, introduced species that become invasive and do damage, or introduced species that do little damage or even result in a benefit?

On the negative side, we have talked about the Hawaiian mongooses, rats, and yellow jackets. There are others; feral pigs and cattle graze on native grasses and other plants. The Formosan ground termite causes millions of dollars of damage to trees and structures each year. Alien plants, such as Florida prickly blackberry and molasses grass smother native vegetation and prevent their re-establishment. As a result of these and other invasives, Hawaii has more endangered species per square mile than any other place on earth. This is due, at least in part, to invasive species.

Other introductions have been moot. For instance, over 4,600 species of plants have been introduced into the Hawaiian Islands over the last 200 years. However, only 86, less than 2% of the total, have become serious problems for native ecosystems.

Horses were introduced to the Americas

by the Spanish in the 16^th century, as were sheep and

cattle. De Soto brought 13 pigs to Tampa Bay in

1539; these were the ancestors of the razorbacks

of the Southeast… and the University of Arkansas.

Some introductions have been wildly successful. Indeed, most of the cultivated crops (except for corn, turkeys, tomatoes, potatoes, and peanuts) and livestock animals in the continental U.S. are introduced species. Your pet cat, dog, bird, fish, or snake is probably an introduced species as well.

Of the approximately 5,000 alien animal and plant species in Hawaii, only about 300 to 500 have gone on to wreak significant damage and some have been beneficial. So the question remains, which are the exceptions- the failures and accidents that have resulted in destruction, or the successes and the accidental introductions that have had negligible effects?

Websites are full of lists of invasive species, the species they are displacing and the lost resources due to their introduction. We don’t see lists of introduced species that have worked out just fine. Perhaps this is as it should be; attention should be paid to those problems that need to be resolved. Attention should also be focused on the failures as a learning opportunity when future introductions are contemplated. But don't assume that a species is a problem just because it was introduced.

For more information, classroom activities and laboratories on introduced and invasive species, see:

Introduced species –

http://www.gcrio.org/CONSEQUENCES/vol2no2/article2.html

http://amphibiaweb.org/declines/IntroSp.html

http://alic.arid.arizona.edu/invasive/sub2/p7.shtml

http://www.flmnh.ufl.edu/fish/southflorida/introducedspecies.html

http://www.saburchill.com/hfns02/chapters/chap022f.html

http://www.physorg.com/news/2011-01-australian.html

http://www.hawaiianencyclopedia.com/polynesian-introduced-plants.asp

http://www.expedition360.com/australia_lessons_esd/2001/09/introduced_species_the_rabbit.html

Invasive species –

http://www.invasivespeciesinfo.gov/

http://www.fs.fed.us/pnw/invasives/index.shtml

http://ei.cornell.edu/ecology/invspec/

http://www.invasivespeciesinfo.gov/resources/educk12.shtml

http://www.oar.noaa.gov/spotlite/archive/spot_illinois.html

http://www.nationalgeographic.com/xpeditions/lessons/14/g68/newsinvasive.html

http://www.fws.gov/invasives/is-activities.html

http://www.nhptv.org/natureworks/nwep15tg.htm

http://www.utoledo.edu/nsm/lec/gk12_grant/Invasive_Species_Game_.html

The Life Of The Party

2011-12-28T08:00:00.005-05:00

Biology concepts – plant adaptations, osmosis, parthenogenesis

Last week we discussed the biological implications of an old Christmas carol. Today’s post is a hodgepodge of holiday biology, but we can still find some exceptions.

From a distance, spruce, fir, and pine Christmas

trees look similar. The differences are mostly in

the needles, both shape and number.

Christmas trees – There are many different types of trees used for Christmas, but they are all evergreens. This is the reason they were used in the first place. The tradition sprung from old pagan ceremonies that reminded us that spring would come and there would be a rebirth of greenery.

Evergreens have a thick wax coating on their needles (these are actually their leaves). This adaptation, as well as the low surface area of each leaf, helps to reduce water loss during the arid winter.

The sap of evergreens is higher in sugar than in other trees species. This keeps the liquids in the tree from freezing solid during the cold months. The higher sugar content oozes from the bark and at the collars of the branches, and is very sticky (picture Chevy Chase in Christmas Vacation).

Evergreen is a characteristic not a botanical grouping. They tend to photosynthesize all winter long, given enough water and sunlight. In deciduous trees there are hormonal (phytohormonal) signals that induce cleavage of the leaves from the stems (abscission) when there is not enough sunlight to justify making chlorophyll. In evergreens, there is some of this signal present, and pines do lose leaves in the winter, just not all of them. When cut and kept indoors, the abscission signal is increased, and together with the reduced water – all the needles end up on your carpet.

The leaves of cedar Christmas trees

look different from other evergreens.

If you choose a red cedar, just remember

that there is actually no evidence that

they keep moths away.

The groups of trees used for Christmas are members of the conifers – cedar, fir, and pine, and spruce. In general, pines have two or three needles coming from the same place on the twig, while fir and spruce usually have just one. To tell fir from a spruce, try to roll a needle in your fingers; if flat and won’t roll, it is probably a fir, but if it is four sided and can be rolled, it is a spruce. Cedars look different from the other three, they have scale-like leaves and ball cones, and their bark is more splintered.

Christmas cactus – This is a small genus of plants, comprised of two groups, the truncata and the buckleyi. In the wild, they grow on other plants (epiphytic) or on rocks (epilithic). They don’t have leaves, common in cacti, their flattened green stems serve as their photosynthetic elements. They occur in naturally in eastern Brazil, along the coast of the Atlantic Ocean. Those for sale in the U.S. are cultivars, bred for hardiness and different colors, different plants will bloom in red, yellow orange, or pink.

Thanksgiving cactus stem is shown on the

top, while the bottom stem is from a

Christmas cactus.

In Brazil, the cacti are called May Flowers, reflecting the month in which they bloom in the Southern Hemisphere. In the northern latitudes, they flower from November through January, depending on the cultivar. This presented a classic opportunity for commercialization.

You might want to look at your Christmas cactus a little more closely; you might actually have a truncata when you think you have a buckleyi. The Christmas cactus has stem segments that are rounded, with more symmetric points. The flowers hang down low and their pollen is pink. These flowers generally bloom later and these buckleyi cultivars therefore termed the Christmas cactus.

The yellow pollen on the left is characteristic of a Thanksgiving

cactus. The pink pollen of the flower on the right is typical of

the Christmas cactus.

In contrast, truncata cacti have much sharper stem segments. If it hurts to prune your cactus, you may have one of these. The flowers stay closer to horizontal, or even rise up on the plant. The pollen grains are yellow, so there are several ways to tell these plants apart. Perhaps the best way is by the blooming time. The truncata will bloom closer to the end of November. For this reason, they are often called Thanksgiving cacti. Still think you have a Christmas cactus?

Fruitcake – I am an unapologetic fruitcake fanatic. To everyone who isn’t - stop making fun and just send them to me.

Fruitcake! It may be my favorite

holiday treat.

The biology of fruitcake is based on bacteria, or more correctly, the lack of bacteria. The candied fruits used in fruitcake are not just dried, they are preserved. For many centuries, fruits were precious commodities, especially in the winter. The vitamin C and other nutrients were needed for good health, but spoilage kept most people from having them during the colder weather.

Meats were preserved with salt, called curing, since the days of the ancients. Fruits, on the other hand, don’t taste so good when salt cured. It turned out sugar that could preserve fruits just as salt cured meats. Either liquid syrup or crystalline sugar would do the job, but sugar was very costly. Honey could do the job, but not as well, and it wasn’t much more available. Therefore, preserved fruits were a luxury for some period of time.

With the advent of sugar beet production in the Americas in the late 1500’s and the resulting availability of sugar in Europe, there was a candied fruit glut in Europe. It became more common to use them in baking. Italian pannatone, and fruitcakes were common uses.

So how do salt and sugar preserve foods? It all has to do with water. Bacteria need water to survive; if you remove the water, you stop (or at least slow) bacterial growth. An osmotic gradient is set up when cells are placed in high salt (hypertonic) or high sugar environment. If the salt or sugar content is higher outside the cell, it means that the water concentration is higher inside the cell.

In osmosis, water flows from where there

is little solute toward where there is

much solute. In hypertonic solution,

this means water leaves the cell.

Water will flow from areas of high concentration to areas of low concentration, just as the salts and sugars will. This is diffusion, but in the case of water it is called osmosis (Plants That Don't Sleep Well). The solvent (water) and solutes (those things dissolved in the solvent) try to balance their concentrations, so water flows out of the cell and salts or sugars flow in. The result is pandemonium, chemical reactions are not possible under these conditions, and the organism either dies or goes into stasis.

Dehydration by salt and sugar work in several ways. One, removing water through osmotic pressure will turn the bacteria, fungi, and parasites already on the food to dried up corpses by pulling out their water. Second, the lack of water in the preserved food stops bacteria and other microbes that might land on them from propagating; no water, no cell division.

Third, the high salt or sugar concentrations, even with some water present, limits the species of organisms that could grow there. Only a few microbes, called halophiles (hal = salt, and phile = lover) can grow in high salt environments. Similarly, honey is only about 30% water, so not many bacteria can grow in this low water/high sugar environment (but some important bacteria can, so don't give raw honey to infants). Finally, the loss of water in the foodstuffs reduces the oxidation reactions that might take place to age the food. Fats are especially susceptible to oxidation, they go rancid in not too long. The curing of meats slows this process, but is less a problem in fruits due to the low fat content.

Those fruitcakes deserve a little more credit, don’t they? And by the way, fruitcakes are not the doorstops everyone thinks they are, they actually float in water.

Virgin birth – I will only touch on this subject, as the blog will soon be delving into a series of stories on mating and reproduction. There are many species of animal that can give birth to viable young without mating. This is called parthenogenesis (partheno = virgin, and genesis = birth).

In 2005, a komodo dragon in a zoo laid some

eggs. No big deal, except she hadn’t been housed

with a male for 2 years! Apparently, they can

reproduce sexually, or by parthenogenesis if

no males around. This has changed how

komodos are housed in zoos.

Parthenogenesis occurs when the unfertilized egg receives the messages necessary to begin to divide and form an embryo. The offspring have only their mother’s DNA with which to work, so they are all clones and all female. The egg does have two copies of the chromosomes, but this can occur in two ways. If the egg is haploid but undergoes chromosome doubling, the resultant offspring is a half-clone of the mother. But if the egg is produced only by mitosis, with no meiotic event to result in a haploid gamete, then the offspring is a full clone.

Many species use parthenogenesis exclusively, or in response to environmental or population conditions. Whiptail lizards, as well as aphids and some plants, are famous for undergoing parthenogenesis. No cases of mammalian parthenogenesis have been documented in the wild, but stem cells have been developed by parthenogenesis in the laboratory. Anyway, if the Christmas story was going to rely on parthenogenesis, then Jesus should have been a baby girl.

Mistletoe is an evergreen that grows

on other plants. It can draw water

from the host even in winter. It also

draws animals to the tree in winter.

Mistletoe – These are evergreen, hemi-parasitic plants that grow in many parts of the world. They have photosynthetic leaves, so they produce their own carbohydrates and energy, but they rely exclusively on their host tree for water and minerals. The mistletoe roots bore into the host bark and vascular tissue to obtain the water and minerals it needs.

The mistletoe can serve to hurt the host plant, especially if it grows too well, but they can also help the host. Junipers that harbor mistletoes produce more berries than those without. This is due to the large number of birds that come to eat the mistletoe berries; the juniper takes advantage. This makes it hard to determine of the symbiosis of mistletoe/host is parasitism or perhaps mutualism.

As the berry passes through the bird,

it releases sticky cellulose fibers that

help the seed stick to an unfortunately

placed branch.

The name, mistletoe, is not something commonly brought up at a holiday party. From the Old English word, “mistiltan,” the name tells it all. Birds eat the fruit and seeds of the plant and some of them pass through the GI tract unaltered. When excreted (mistil means dung), the sticky seeds may germinate on a limb (tan means branch). Interesting, but try not to mention it over a bowl of holiday punch.

The white berries of the mistletoe played a role in the 18^th century Christmas kissing tradition. In Scandinavia, the maid under the mistletoe could be kissed, but the gentleman had to pull off a berry each time. While the berries were gone, the kissing privilege was lost.

Next time we will finish our stories on sleep and activity by talking about introduced species. Then we will start a series of posts on the incredible worlds of water and salts in biology. Our fruitcake discussion above may serve as a great introduction, but it is just the tip of the iceberg.

The concepts discussed here will be discussed in more detail in other posts. Resources will be provided on those occasions.

Twelve Days Of Christmas – Biology Style

2011-12-19T08:00:00.020-05:00

Biology concepts – introduced species, cross breeding, courtship rituals

We are finishing a long series stories on sleep and activity patterns, but I thought we might take a break and talk about the holidays. How about a couple of posts concerning the ways Christmas can be viewed biologically? We will return to activity patterns and Hawaii after the new year.

Lets examine the carol, “The Twelve Days Of Christmas.” Initially published in England in 1780, it was probably a British memory game before it was a carol, but older versions in France suggest that it came from that country originally. The twelve days of the lyric are from Christmas Day to the Epiphany (the baptism of Jesus of Nazareth).

Many interpretations of the song exist, from the devoutly religious to the idea of managing a country estate. For our purposes, lets stick to biological explanations of the gifts. Keep in mind that they were given by one’s true love; many have to do with family, love, and faithfulness – sounds more like a warning than a gift to me.

There are four subspecies of red-

legged partridge: French, Spanish,

southern Spanish, and Coriscan.

The English version is the Corsican,

even though it was imported from

France.

A partridge in a pear tree – A partridge is a small game bird, a member of the pheasant family. The red-legged partridge is an introduced species; it was brought to England from France in the 1600’s as target practice for Charles II. The red-legged partridge is known to roost in orchards, including pear trees - hence the pairing of the gifts.

This bird is exceptional in that it often lays eggs in two different places. The female incubates one clutch while the male incubates the other. Their loyalty, devotion to family, and fidelity are plausible reasons for their inclusion in the song. This is further supported by another behavior of the female partridge. She will feign injury to draw the attention of a predator and protect her babies.

Two turtle doves – These members of the dove family are also a symbol of devoted love, since the males and females were imagined to mate for life. This turns out not to be true, as a study in 2008 shows that the hens will mate with bachelor males as well as males from other bird species. These hybrid crosses in other animals often result in non-fertile offspring (like mules, which are crosses between horses and donkeys), but the offspring of dove crosses are often fertile.

The Crevecoeur chicken is much like

the Houdan, but the Crevecoeur only

has four toes!

Three French hens – This might refer to cross-bred chickens. In the 1600’s, chickens were brought to France from the East and bred with French poultry. The Crevecoeur (named for the town in Normandy) breed is probably related to the Polish breeds. The very ornamental Crevecour is now only bred for poultry shows and is not eaten. Two other french breeds (three total) also originated around this same time, perhaps this is why they were used for the third gift.

Some believe that the chickens were included in the song because a rooster crowed at the birth of the baby Jesus. So shouldn’t the gift in the song be three French roosters? More likely it was because the hen represented motherly devotion and love.

Four calling birds –History suggests that calling birds was actually “collie birds,” another name for blackbirds (collie came from coal, as in coal-y = black like coal). The blackbird is a true thrush, common to most of western Europe. These were fairly common birds in the 1700’s, and were trapped in barns and the like to supplement the diet. They became a delicacy.

While the first four gifts all refer to birds, only the first three bring connotations of love and fidelity. The fourth is mostly commonly associated with eating. Which of these things is not like the others?

The male pheasant has the golden rings.
Does he give one to the plainer female during
courtship? Male ornamentation is common
in lower animals; in humans it looks silly,
pinkie rings and a one earring.

Five golden rings – Maybe we were just starting a new pattern, since the five gold rings also refers to eating a bird. Golden pheasants have five or more golden rings on their necks, and they were often served at royal and other high society feasts.

Pheasants and partridges are closely related; they come from the same family of Phasinidae. While they are very different in size (about 7 inch quails to 30 inch pheasants), they both have short, powerful legs that allow they to run quickly along the ground to elude predators.

Giving your true love five gold rings is overkill anyway, right?

Six geese a-laying – Still with the birds - how is it that the Audubon Society hasn't adopted this song as their anthem? In the carol, the geese may serve two purposes. One, they were bred for better egg laying, up to 50 eggs per year. This made them symbols of fertility. Second, they were often served as Christmas dinner – remember the prize goose the reformed Scrooge purchased for the Cratchits.

The indigenous wild boar was originally the choice for Christmas feasting, but was hunted to extinction on the island by the 13^th century. It was reintroduced later, but turned into a nuisance by eating all the crops. Consequently, it was hunted to extinction in England again by the late 1700’s. Imagine the kind of protests that would occur nowadays if a species was about to be eliminated for second time in the same place! Even today, a string of sausages is often placed around the goose’s neck as a reminder of boar’s place on the table.

The male (cob) and female (pen) swan will

mate for life. If one dies, the other will remain

alone for the rest of its life.

Seven swans a-swimming – Because swans could both swim and fly, they were revered in many ancient cultures. Waterfowl (Anatidae family, includes ducks, geese and swans) may have evolved from the galliformes (order including chickens and our friends the pheasants and partridges). This is the majority opinion, but some scientists believe that they descended from shorebirds. This is believable, they already lived on the shore; it was a short trip to adapt to the water.

King Edward used swans in his coronation in 1304, and other royal families then adopted their use across Europe. As such, all swans in public were the exclusive property of the monarch (landowners could have some on their property), and were seen as precious, just like the adoration of your true love. Oh, and they ate them at Christmas too. Apparently, during this time period, the way to another’s heart was through their stomach, and birding.

Personally, I think of Edward Jenner when
milkmaids are mentioned. He recognized that
they didn’t get smallpox, only coxpox. He used
this knowledge to develop a smallpox vaccine.

Eight maids a-milking – The first seven gifts were all birds, but the last five gifts are all humans. Is that a step up or a step down? As for the milkmaids, we have two ideas implied; one is food, and the other is romance (or just lust).

In the 1700’s there was no refrigeration, so milk products were short-lived and therefore precious. Giving a loved the ability to have fresh milk would mean many holiday treats, like custards and cheeses. Food and banqueting are sure playing a big role in this song.

The other use of this gift is slightly less savory. In France, the milkmaid was a sign of fertility; big-busted and fit. In England, to ask a young lady to go a-milking could be a legitimate proposal of marriage, or an illicit proposal of hanky-panky. Either way you take it, this is a loaded gift, biologically-speaking.

Nine ladies dancing – The rest of the gifts have to do with musicians and dancers. Basically, the gift-giver was hiring a band and entertainment for his/her true love's banquet.

Dancing is often considered the human equivalent of sexual selection behavior in animals. Indeed, the psychologist Geoffrey Miller deduces that human culture of all types developed as a type of sexual selection, which, along with natural selection, forms the basis of evolution.

Is this a female or a male squinting bush

brown butterfly? What if I told you it has

been warm and rainy the past few weeks.

Females dancing as a courtship ritual is an exception. Usually males display and try to draw the attention of the female. However, in one species of cichlid fish, the striped kribensis, the females do dance for the males, brushing their large pelvic fins against the male. Males will most often select the females with larger pelvic fins.

Other species will have the females dance – sometimes. In the squinting bush brown butterfly, it all depends on the temperature when the caterpillars mature. If cool, then the females will develop large ornamental spots and will dance to attract males. If they mature in warmer, moist conditions, the males will have the spots and will dance for the females.

Ten lords a-leaping – The males of many species dance as a part of courtship. Jumping spiders have an elaborate dance that is meant to show off their iridescent hairs and bright abdomen. They also vibrate or twitch their abdomens and legs (click for a video link) to make a purring sound as well. Grebes (birds) have a mutual dance and run that the male and female perform together, both as part of initial mate selection, and then repeated to reinforce their bond (click for video).

In a positron emission tomographic (PET) image,

yellow and red mean more activity. Notice how words

(bottom left) and music (bottom right) seem to

activate different parts of the brain. Pleasant music

activates positive emotional centers.

Eleven pipers piping – Commonly, the pipers are shown to be playing flute or other recorder-type instruments, but I think that the bagpipes might be more accurate historically. The best biology I can do for the bagpipes is that they are supposedly a source of music, they are meant to generate positive emotions – music soothes the savage beast. PET scans confirm that dissonance in music activates the negative emotion centers of the brain. For me, the pipes are quite dissonant.

Twelve drummers drumming – This final gift may relate to the rhythm of the drums. Anthropologists talk about drumming in terms of emulating the beating heart. This brings us back to romance and love, and in a sense, drums are then the truest form of biological music.

If we return to the banquet motif that has pervaded so much of the gift giving here, drums were late coming to England and Europe. They were teamed with the trumpets that would announce the arrival of the next course during the banquet. How could they possibly notice the next course with all those ladies dancing, lords leaping, and pipers piping, not to mention all the birds hanging around?

You probably didn’t realize there was so much biology in a Christmas song - but biology is everywhere. Next time we will investigate the biological aspects of a few random holiday traditions. For example, in many lizard species virgin births are no big deal.

All the concepts here will be explained in more detail in the near future, resources for each will accompany their explanations.

When The Early Bird Is Also The Night Owl

2011-12-14T08:00:00.052-05:00

Biology concepts – cathemerality, circadian rhythm, adaptation, predator/prey relations

One carnivorous and three vegetarian friends

stranded on a island – what could go wrong?

The 2005 movie ”Madagascar” had some animals that we recognize from zoos; a lion, a zebra, a hippopotamus, a giraffe. But who were the bad guys? They were called the “Foosa” but what kind of animal was the foosa? And who were those little primates they were trying to eat?

Being an island, Madagascar has developed ecosystems all its own. There are plants and animals that live there and nowhere else on Earth. This can lead to some interesting and exceptional behaviors and activities.

Tenrecs are a weird group. Different species can

be a few grams to over a kilogram, may have between

30 and 45 teeth, are related to elephants, and a have

a common anal and urogenital opening like birds. With

all that going on, being blue and yellow doesn’t seem

that weird.

Madagascar has its share of diurnal activity (daytime) and even more activity under the cover of dark (nocturnal). The streaked tenrec (Hemicentetes semispinosus, one of about 30 species) is crepuscular (active at dusk and dawn), so that activity pattern is covered as well. This black and yellow-striped cross between a hedgehog and a shrew (just by the looks of it, not by parentage) feeds on worms and other invertebrates. A study from early 2011 described a unique behavior from the tenrec, one that may cause us to include the cricket in the tenrec’s ancestry.

The quills on the tenrec come in two sizes, the long ones are for protection, but the shorter ones can be rubbed together to make high pitched (ultrasonic in many cases) sounds that can be used for communication or navigation. In the low light conditions of sunrise and sunset, scientists are considering the idea that tenrecs use stridulation (making sound by rubbing body parts against each other) to echolocate in their surroundings, similar to bats. They can also keep tabs on one another, communicating constantly with other tenrecs, even with a mouthful of worm.

The short spines on tenrecs are controlled by individual

muscles, so that one spine can be rubbed against another

to make noise.

Crickets, beetles, and some vipers stridulate, but the tenrec is a stridulating exception in two regards. One, it is the only mammal known to do so; and two, it is the only animal of any kind known to communicate both vocally and by stridulation. Madagascar would be a cool place to visit – weirdness like this is around every corner.

Even though the tenrec is a Madagascar native, I didn’t see him anywhere in the movie. Some animals are too weird even to be believable in a cartoon about talking animals.

The movie did feature a primate group from Madagascar, one that had a penchant for dance. Lemurs (from Roman mythology, lemurs = ghosts) are playful and energetic, and some are even said to dance, but I don’t think they crave house music like in the movie. The Sifaka verreauxi is called the dancing lemur, as it is the exception to four legged motility among the lemurs. S. verreauxi walks on two legs, but the outward turn of their hips make them sway back and forth, like they are dancing.

Lemurs of the genus Sifaka bounce around on two

legs to cover ground quickly. This looks like dancing, and

probably gave the movie makers the idea to turn the

lemurs into a group of party animals.

In the movie, I saw no less than seven different types of lemurs, but in truth there are about 100 lemur species and subspecies live on Madagascar and the nearby Comoro Islands (and nowhere else). Together, they are a microcosm of Madagascar activity patterns. Some lemurs species, like the large Sifaka verreauxi, are diurnal, while the smaller species, like the aye-aye, are generally nocturnal. Some are even crepuscular, active at both dusk and dawn (so they are not vespertinal or matutidnal). But the weirdest types of lemurs are those that don’t show any of these patterns; in fact, they show no pattern at all! If that isn’t an exception, I don’t know what is.

The lack of an activity pattern does have a name, cathemerality (from the Greek, cat = complete and hemera = day). Cathemeral animals are active for periods of the day and/or periods of the night. In some cases, the periods of activity are driven by competition, when competitors are resting or prey is active. In other cases, periods of activity might be influenced by the seasonal temperatures or even the phase of the moon.

Whatever the stimulus, cathemeral (sometimes called metaturnal) animals can sleep day or night and hunt day or night, with no period of adjustment needed. African lions are cathemeral, driven by hunger and the success rates of their hunts, or by a need to conserve water.

In Madagascar, the red-fronted lemur (Eulemur fulvus rufus) is cathemeral in activity, as is the blue-eyed black lemur (Eulemur macaco flavifrons). Among primates, only humans and this species of lemur have blue eyes. However, the males have black hair while the females are reddish, so there is no chance of little blonde-haired, blue-eyed lemurs.

It is called the blue-eyed black lemur, so why is it

reddish-brown? This species is sexual dichromatic;

picture above is of a female, only the males are black.

The blue-eyed black lemur sees in color and is generally adapted to diurnal living; this is witnessed by the increase of its nocturnal activity when there is a full moon and with the nocturnal light level in general. However, the blue-eyed lemur has at least some activity spread across the 24-hour day all year round. This is one of three cathemeral patterns of lemurs in Madagascar lemurs.

A second cathemeral pattern is seasonally driven. In summer, when the daylight hours are greatest, it is enough for some cathemeral animals to limit themselves to daylight activity, but expand their active hours a bit during winter, so they are active in both day and night. This is driven by a need to find sufficient food.

The third cathemeral pattern is one in which there is mostly diurnal activity in one season and mostly nocturnal activity in another season. This may be driven by changes in temperature or perhaps resource availability. In Madagascar, the tropical climate ensures that food is always available, and the lack of a winter means that the temperature ranges between 60˚F and 80˚F all year round.

The diets of the red-fronted lemurs and the blue-eyed black lemurs are very different considering that they are closely related species, called true lemurs (eulemurs, eu = true). Red-fronted lemurs eat only leaves, while blue-eyed black lemurs eat fruits. But they are both herbivores, and are both potential meals for a predator. This would be a good reason for being cathemeral; the lemurs can just choose to be active when the predator isn’t. Great idea, huh? Well, Madagascar’s biggest predator apparently read the lemurs’ playbook.

The fossa is not a cat, it is not a mongoose, it is not a monkey.

It is a predator and it is found only in Madagascar. It has

retractable claws, the same as all cats except the cheetah.

The fossa (pronounced foosa - get the connection to the movie?) is really Madagascar’s only big predator. It looks like a cat as it walks, and has retractable claws like most cat species, but its tail is as long as its body, like a monkey or a lemur. The fossa’s snout is more mongoose-like, as is the length of its body compared to the length of its legs. The film version of Madagascar didn’t do justice to the physical nature of the fossa; the bad guys pass for large cats.

The fossa spends much of its time up in the trees (it is arboreal) and chases the lemurs from tree to tree. Its long tail and sleek body design help it to move and maintain its balance as it moves through the branches. Most interesting, and an exception to mammal body design, the fossa’s outside digits on its rear paws are its biggest, this helps it to grasp the surfaces of the trees.

The long tail of the fossa helps it chase down

lemurs in the trees by improving its balance.

It also helps that the fossa hunts lemurs in

groups, using cooperative strategies.

Up in the trees we have the lemurs; some diurnal, some nocturnal, some crepuscular, and some cathemeral. What a buffet for the fossa! No matter what time he (or she) wishes to dine, there could be lemur on the menu, so the fossa has adopted cathemerality as well.

The movie was accurate in showing the fossas and lemurs active in both day and night now, but did the lemurs become cathemeral to get away from fossas? Maybe. The lemurs evolved before the fossa; were they cathemeral because they didn’t have to worry about predation, and a few species have stayed that way? Could be. Did the fossa become cathemeral to take advantage of the lemur smorgasbord? Nobody knows –yet. You can be sure that there are scientists who support each possibility.

Whichever way it happened, it points out a wrinkle that few people consider. Some animals can actually change their activity pattern. The shift is often in response to some ecological or physiologic pressure. Skunks are crepuscular - except for males in the mating season - they become diurnal.

Another example is the short-eared owl of the Galapagos Islands. The owls are crepuscular on islands that have a predatory buzzard species, but on islands without buzzards, the owls are diurnal. Finally, some anole species change their activity pattern from diurnal to nocturnal as the temperature rises. Even their color can change from green to brown as the temperature changes.

These shifts in activity patterns occur often enough that they can’t be called exceptions, but the majority of animals do hold a single pattern throughout the year. As such, nocturnal animals interact with other nocturnal animals and the same with diurnal animals. This isn’t a tough concept to grasp, even the movie got it right. Unfortunately, some folks in 1880’s Hawaii just didn’t seem to understand, and they are still dealing with the problems it caused.

For more information and classroom activities on cathemerality, lemurs, or fossa, see:

Cathemerality –

http://www.ips2004.unito.it/Sym_Curtis.html

http://www.ncbi.nlm.nih.gov/pubmed/16415576

http://www.hindawi.com/journals/ijz/2011/362976/

http://www.deepdyve.com/lp/taylor-francis/avoiding-commitment-cathemerality-among-primates-kyInyZRVTH

Lemurs –

http://www.ncbi.nlm.nih.gov/pubmed/16415576

http://www.nhbs.com/lemurs_of_madagascar_diurnal_and_cathemeral_lemurs_tefno_160645.html

http://www.lemurs.us/basics.html

http://nationalzoo.si.edu/Animals/Primates/Facts/FactSheets/Lemurs/default.cfm

http://www.globio.org/glossopedia/article.aspx?art_id=49

http://www.pbs.org/edens/madagascar/class1.htm

http://www.magpi.net/Community/Programs/Madagascar-Conserving-Biodiversity

http://www.lemurreserve.org/programs.html

http://www.animalcorner.co.uk/rainforests/lemur.html

http://www.actionbioscience.org/evolution/roberson.html

fossa –

http://animals.nationalgeographic.com/animals/mammals/fossa/

http://www.sandiegozoo.org/animalbytes/t-fossa.html

http://www.edgeofexistence.org/mammals/species_info.php?id=43

http://www.environmentalgraffiti.com/animals/news-one-weirdest-predators-earth-fossa

http://www.zooborns.com/zooborns/fossa/

http://www.pbs.org/wgbh/nova/madagascar/classroom/l2_intro.html

Sunrise, Sunset – Life In the Twilight

2011-12-07T08:00:00.055-05:00

Biology concepts – activity patterns, crepuscular, co-evolution, active pollination

Nocturnal and diurnal activity patterns are like vanilla and chocolate cupcakes. But what if you like rose hip or green tea flavors – are there cupcakes out there for you?

Who knew lizards like cupcakes. I bet they just lick

off the icing.

In a word – yes. In fact, there are so many organisms that are neither nocturnal nor diurnal that I hesitate to call them exceptions – like how everyone has mocha cupcakes now. And I bet you know some of animals with extraordinary activity…… ever heard of sweat bees or deer or infants?

Diurnal animals have developed color vision and ways to deal with the heat and the sun. Nocturnal animals have sensitive vision and other adaptations to make use of the dark. But there are some animals that are active on the edges of both situations; dawn and dusk. What adaptations would help an animal succeed in this niche?

In general, crepuscular (latin for twilight) animals have vision most like nocturnal animals. A tapetum lucidum (Form Follows Function) is present behind the retinas of many crepuscular mammals. Your cat is crepuscular, although she will adapt to a diurnal pattern as a pet…..if she feels like it, you know how cats are.

Those great light shows put on by nature in the evenings

have a name – crepuscular rays. Impressive trivia

for your next party. Photo by van049.

There are advantages to crepuscularness (I just now invented that word). By curtailing activity during the heat of the day, less energy is spent conserving water. Not surprisingly, many desert species are crepuscular. Heat, on the other hand, doesn’t seem to be as much of an issue, since there are endothermic as well as ectothermic species that are active in these time frames, for instance desert lizards like the gila monster.

The dim light available at dawn and dusk is also an advantage for crepuscular animals. There may be enough light to see, but not enough to make these animals stick out like a sore thumb. This works for deer; along with their coloring, the dim light helps them blend into the background. Deer caught out during the day become very stressed and confused. They may end up playing in traffic; just a case of clouded judgment due to sunshine.

The aim of the crepuscular pattern is often to reduce the chance of being eaten. Most terrestrial predators are diurnal or nocturnal (except for several cat species), so crepuscular animals are active after diurnal predators have had their warm milk, and before nocturnal animals drink their coffee.

Chimney swifts perch on vertical surfaces and

have saliva that dries like glue and is practically

insoluble. They use it to build nests on chimney

walls. They have weak claws and can’t perch on

branches, they can perch on vertical surfaces

using their stiff tail feathers, but mostly they just

fly 16-18 hours each day.

Slightly more common are the crepuscular birds, including the American woodcock, which is a ground bird that eats worms and nests in brushy young forests. The chimney swift is also crepuscular, but it nests in chimneys and other vertical surfaces, eats insects out of the air, and can maintain flight for an entire year. These are birds with very different behaviors, diets, and ranges, but are both crepuscular. As is the rule in nature - maybe the only rule without an exception - it is impossible to predict the behavior of one species based on characteristics similar to other species.

In the plant/pollinator part of the community, some crepuscular pollinators have developed special relationships with plants that flower in the evening only. This represents a special form of crepuscularness (there’s that new word again, I think it will catch on) called vespertinal (vesper = evening in latin) activity. These plants and insects are active only in the evening, and often co-evolve mutualistic relationships.

In the desert where the Joshua tree lives, water is at a premium, and the heat doesn’t help the water situation. Remember in our discussion of nastic movements (Plants that Don’t Sleep) we saw that turgor pressure of water is responsible for the opening of the flowers. But open flowers promote water evaporation! Therefore, the best strategy for the Joshua tree is to have its flowers open outside the heat of the day. Et voila - it is vespertinal.

Joshua trees are native to the Mojave desert. They

were named by the Mormon settlers who were

reminded of Joshua raising his arms in prayer.

Predictions are that 90% of the trees could be wiped

out by global warming by the year 2100.

The price of water also has also driven the Joshua tree to produce no nectar – it must have some other way to attract the yucca moth. It is the yucca moth who really taken this upon its (her) shoulders. She has found a way to make pollinating the Joshua tree flowers pay off for her species. But only the yucca moth has made this connection, and this makes their relationship an exception to a biological rule.

Since they are available to one another in the same part of the day (evening) it is more likely that vespertine plants might have a single pollinator, which we learned a few weeks ago (The Perils Of Plant Monogamy) is the exception to the rule of multiple pollinators.

The female yucca moth is not drawn to the flowers by nectar, but by the need to propagate her species. At one flower, the female moth gathers pollen and balls it up into a large mass. Palps (appendages like arms but located near the mouth) hold the pollen ball as she travels to another Joshua tree; almost always to another tree. We know that cross-pollination is better than self-pollination (Is It Hot In Here), but the question remains, how does the moth know that?

At a second tree, the yucca moth lays an egg inside the carpal (which houses the ovule and is where the seeds will form once the flower is pollinated), but only in one or two of the many caprals. Then the moth swipes the pollen ball over the stigma (the top of the carpals), ensuring that the seeds will develop.

Most pollinators are passive, they transfer pollen as a result being drawn by some attractor (nectar, odor, color, etc.). Pollen transfer is not the reason for their visits. But yucca moths are an exception to this rule; they are active pollinators. They visit the flowers with the express intent of collecting and transferring pollen. But why spend energy to purposefully pollinate?

In the left image, you can see the palps that the yucca moth uses to gather up a pollen ball. These are modified mouth parts, and mouth parts are modified ancient legs. The middle image shows the yucca moth actively pollinating the flower after it laid its egg inside the carpal. The right image shows the larvae growing inside one ovule tube (the top-left cavity), eating the seeds as food.

The seeds are the payoff. The moth larva eats the seeds of that one carpal while developing. This is symbiotic mutualism, both species benefit from their relationship – food for the moth larva, and sure pollination for the Joshua tree.

But certain precautions must be taken. Production of seeds (and fruit) takes energy. If the flower won’t produce enough seeds to make it worth the energy expenditure, the tree will abort the flower. So, if moths deposit eggs in too many carpals of the same flower, the larvae will eat too many seeds, and the flower will commit suicide. This will kill the larvae as well. To prevent this, the moths emit a chemical scent to indicate that a flower has been visited and pollinated; other moths will move on to flowers that have not been marked as occupied.

The yucca plants and yucca moth are an example of the vespertine lifestyle, but are there organisms that live exclusively on the other edge of the night? Yep.

Several types of bees are active only in the early morning hours, just after sunrise. This type of activity pattern is called matutinal (Matuta, the Roman goddess of dawn). Some flowers open up very early in the morning, and these are the targets of matutinal bees. The morning glory is a good example, although the flowers remain open long after the early bird bees have gone to bed.

This is the false dandelion. Sweat bees and

schinia moths appreciate for giving them

food and helping in reproduction. I appreciate

it for not being a true dandelion– the lawn

care expert’s mortal enemy!

Other matutinal flowers include the plants of the pyrrhopappus family. These are perennial herbs of the American southwest, south central, and southeast grass lands, and include the carolinus species that is called a false dandelion. They flower for two-four days a year, opening at sunrise and closing by 10:00 am on a hot, sunny day.

The matutinal flower moth (schinia mitis) and the sweat bee (Hemihalictus lustrans) have relationships with the pyrrhopappus plants. The bees use them as their exclusive source of pollen, although they must visit other flowers, like the morning glory, for nectar.

The Schinia mitis moth is more dependent on pyrrhopappus than are the sweat bees. Food, shelter, mating, and a place to lay eggs are all supplied by these specific herbs, as well as shelter and a food source for the larvae. The moths mate on the open flowers between 7:00 am and 9:45 am (rain or shine), and the female then lays the eggs deep within flower.

The mitis moth egg is laid deep within

the false dandelion flower for protection.

Its going to cramped quarters for the larva.

The reason for flowers developing a matutinal lifestyle might be similar to those for vespertine or fully crepuscular species, ie, water and energy savings. But the pollinators, especially the bees, seem to have followed suit for other reasons. True sweat bees (many people misidentify them) take advantage of the early morning hours to avoid the lines at the flowers; it is a simple matter of reduced competition. On the other hand, the mitis moth has co-evolved with the flower and become completely dependent upon it. If the flower is open only in the morning, the moth better be ready on time.

Who knew that so many plants and animals had thrown off the yoke that tethered them to either day or night activity, and now work at the edges of both? Next time we will take it even further; some organisms have stopped working on any schedule at all.

For more information, classroom activities, or laboratories on crepuscular activity, yucca moth reproduction, or Schinia mitis moth reproduction, see:

Crepuscular activity –

www.emnrd.state.nm.us/prd/.../5thGradeAnimalAdaptations.ppt

http://www.bio.davidson.edu/people/midorcas/animalphysiology/websites/2010/Pacious/DiurnalNocturnalCrep.htm

http://www.circadian.org/dictionary.html

http://www.enotes.com/topic/Vespertine_%28biology%29

http://www.gleaming.org/crepuscular/

http://yomi.mobi/egate/Crepuscular/a

Yucca and yucca moths –

http://waynesword.palomar.edu/ww0902a.htm

http://indianapublicmedia.org/amomentofscience/yucca-flowers-and-yucca-moths/

http://www.emporia.edu/ksn/v41n2-june1995/KSNVOL41-2.htm

http://www.insectman.us/articles/butterflies-and-moths/yucca/yucca--plant.htm

http://www.desertusa.com/animals/yucca-moth.html

http://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/yucca_moths.shtml

http://bss.sfsu.edu/holzman/courses/Fall99Projects/yucca.htm

http://www.blueplanetbiomes.org/joshua_tree.htm

http://www.willamette.edu/~csmith/SCRP.htm

False dandelions and moths –

http://www.eattheweeds.com/pyrrhopappus-hypochoeris-dandelion-impostors-2/

http://www.cas.vanderbilt.edu/bioimages/species/pyca2.htm

http://www.worldfieldguide.com/wfg-species-detail.php?taxno=18360

http://www.butterfliesandmoths.org/species/Schinia-mitis

http://www.jstor.org/pss/25084173

Form Follows Function - It’s About Time

2011-11-30T08:00:00.006-05:00

Biology concepts – circadian rhythm, vision sense, adaptation, parasitism, form follows function

The sun and the moon are symbols of different

activity cycles. As with everything else, we have to give

them human characteristics (anthropomorphism).

Many animals are active in the day or the night, but not both. So what are humans, diurnal (active in the daytime), nocturnal (active in the nighttime), or something else?

Maybe humans are two species, because I know folks who can’t accomplish anything before noon, and do their best work after 11:00 pm, whereas I get up around 5:00 am and am pretty much useless after 8:00 pm.

Whether diurnal or nocturnal, organisms are physically and behaviorally adapted to their activity pattern. This includes the way they sense their environments. Diurnal animals are more likely to have color vision, while nocturnal animals may only see in black and white. The upside for nocturnal animals is greater visual sensitivity, so they can see better than diurnal animals in low light conditions.

The reasons for these different visual talents lies in the types of light receptors on the retina. Rods sense light, but only its presence or absence (white/black). Different receptors, called cones, detect various wavelengths of light (colors). Diurnal animals have about 5-10 times more cones than nocturnal animals (3 types, one for yellow, one for green to violet, and one for red to orange), but they only function in higher levels of light. Therefore, the greater number of rods in nocturnal animals allow for more sensitive night vision, a good thing to have if you are active after sundown.

Rods (yellowish) and cones (blue) are different light receptors located on the retina. Rods are more numerous and detect low levels of light. Cones are less numerous and sense colors of light, but require more light. As shown in the middle image, the tapetum is located beneath the retina in some animals, and can bounce light back to the retina. This bouncing around is responsible for animals glowing eyes at night.

Many nocturnal species have an additional adaptation to improve their night vision. Their retina has an iridescent layer called the tapetum lucidum that bounces the available light around so it may hit more rods. This improves sensitivity, but at a cost to acuity (the image gets a little fuzzier). When you shine a flashlight in the woods at night, the little pairs of reflections you see are the tapetum lucida of the animals looking back at you. The light bounces around inside the eye and some escapes back out through their pupils and that is what you see. Some look at your flashlight to see if you are a predator, others look to see if you are worth eating.

Humans don’t have a tapetum lucidum, so when reflected light bounces off our retinas and back out the pupils, they appear red like the retinal blood vessels and tissues. This is the eerie red eye effect on some flash photography. I always thought it was a sign of vampirism!

Other nocturnal animals, like many owls, rely on hearing and smell more than vision. They are adapted to maximize these senses. We have discussed previously the changes in owl anatomy (Do You Have To Be Ugly To Hear Well) as examples of form following function to improve hearing. Other animals, like raccoons, have a heightened sense of touch. Their paws have elongated sensor pads, and thousands of touch receptors. With these, raccoons can differentiate textures well enough to tell if a fruit is ripe or not, even in the darkest night.

Raccoons have a strong sense of touch for moving around in the dark.

Their elongated paws have thousands of touch receptors to increase the

sensitivity of this sense. On the dorsal (back) side of the raccoon’s paw,

whiskers (vibrissae) on the ends of their digits heighten the sense of touch.

Raccoons don’t even have to touch something to sense it; they have vibrissae (whiskers) on the ends of their digits, above their claws. Whiskers in general are a potent aid to nocturnal animals, whether located on faces, paws, or bodies (remember the naked mole rat’s whiskers on its torso in Take Off Your Coat And Stay A While).

Even plants can be adapted for nocturnal activity. Moonflowers, night-blooming philodendrons, and other flowers that rely on nocturnal pollinators tend to be white (since their pollinators most likely can’t sense color), and strong smelling. Indeed, the increased temperature of the P. selloum spadix (Is It Hot In Here Or Is It Just My Philodendron) is an adaptation to nocturnality.

So why be nocturnal? Anyone who has tried to negotiate an unfamiliar room in the dark knows that being active in the dark brings certain obstacles that must be overcome. There must be distinct advantages to it or needs for it, or else nature wouldn’t go to the trouble of adapting. Some scientists believe that nocturnality arose from originally diurnal organisms taking advantage of an underused ecological niche. Being active at night can be a form of crypsis (hiding), either to make them better hunters, or to avoid being hunted.

Nocturnality can also reduce the amount of water lost to the environment, and can lower the thermal stress on certain species of animals. For example, many frogs lose water through their skin, so daylight and higher temperatures can dehydrate them quickly.

That doesn’t mean that certain species won’t be exceptions. Moths are all nocturnal, except for the polka-dotted wasp moth, that is. There are four species of wasp moths, all diurnal, but the polka-dot is the prettiest, so we will fall into that old trap and give the pretty one all the attention. Diurnally active, this moth has abandoned many of the nocturnal adaptations of its brethren.

The polka dot moth has color and patterns that might be useful

for mating or for warding off other animals, but they would

be wasted if the animal was nocturnal.

For instance, it is beautifully colorful, a no-no for nocturnal moths. Since color doesn’t show up at night, moths are generally white, tan, or grey. Second, the coloration, especially the bright rump, mimics a wasp (hence the name) and warns of a toxic mouthful if consumed. This defense is called aposematism (apo = away from, and soma = body, basically, keep away from me). Many brightly colored insects will make predators sick, purely a diurnal method of survival, as the warning colors would be of no use at night.

Just as this moth species is diurnal when its close relatives are nocturnal, there is a single genus of primate that has chosen to be nocturnal when all others, including humans, are diurnal. Owl monkeys (8 species) live in Central and South America, and leave their sleeping sites about 15 minutes after sunset each day. They forage for fruits and the odd flower or insect until just before sunrise, then retreat to a hollow tree or within dense foliage to sleep away the day.

Owl monkeys adopted a nocturnal pattern after millions of years being diurnal, so it must have afforded them some advantage or was an answer to some overwhelming stressor. They have adapted by developing larger eyes, with more rods and fewer cones. They still see color, but less so than other monkeys.

The owl monkey is nocturnal, so it needs to have more sensitive vision.

For this reason, it eyes (and eye sockets) are huge! Compare the eye

size and skull morphology in the diurnal capuchian monkey. Form of

the skull follows the functional capacity of the eye.

Owl monkeys are interesting to science for being the source of another exception, as they are the only primates susceptible to the human form of malaria. In The Perils of Plant Monogamy, we used malaria in chimps and humans as an example of divergent evolution; malaria developed into species-specific forms. But the owl monkey is susceptible to both the primate and human species, so they can substitute for humans in malaria research.

Malaria is caused by a parasite, and as such, depends on its host organism for nutrition. The rule is that parasites are active when their host is active (feeding). A good example is the intestinal parasite of the surgeonfish, E. fishelsoni (Of Fish Guts And Cancer).

As I am sure you have committed to memory and made a part of your life, E. fishelsoni grows to an amazing size and replicates its DNA thousands of times before it divides into two or three progeny organisms. It takes tremendous energy for a bacterium to grow 80 fold and produce 85,000 copies of its DNA in one day, so it must occur when nutrients and carbohydrates are plentiful - during the day when the fish is feeding. Although it is a stretch, I guess you could call E. fishelsoni a diurnal parasite.

The malaria parasite, Plasmodium falciparum, has chosen a different path. P. falciparum’s host is man, and man is diurnal (teenagers and third shift workers excepted), but the parasite works to produce many progeny (gametophytes) and have them mature in the nighttime. The reason is simple; malaria has two hosts.

Plasmodium falciparum needs two hosts to complete its life

cycle. One immature form (sporozoite from oocyst) grows

only in the mosquito, while another (gametocyte) forms only

from mature sporozoites in the human red blood cells.

While one stage of the organism grows in the human, another needs to be inside a mosquito in order to complete its life cycle. After finishing its development, it is ready to be injected into another human when the mosquito feeds again. The key is that the mosquito is nocturnal and the gametophyte is short-lived. The gametophyte must be produced and mature just in time to be sucked and deposited into the mosquito gut. P. falciparum has pressured to conform to the activity of one host while it is inside a host with the opposite activity pattern.

It is common that most species within a group will have similar activity patterns, since they are derived from common ancestors and therefore many characteristics are similar, including those that determine fitness for day life or nightlife. But there are exceptions. For instance, most rodents are nocturnal, but we see squirrels all day long - they are diurnal. Also, we mentioned above that most primates are diurnal, but the owl monkeys are nocturnal.

But there are bigger exceptions, organisms that aren’t diurnal or nocturnal. Ants, primates, and cats have species that are all over the place; some are nocturnal, some are diurnal and some are neither. It is the in-betweeners and the neithers that we will talk about next time.

For more information or classroom activities on activity cycles, night vision or adaptation, see:

diurnal/nocturnal –

http://zoogirl-zootopia.blogspot.com/2010/08/nocturnal-diurnal-and-crepuscular.html

http://www.desertmuseum.org/kids/oz/long-fact-sheets/Title%20Page.php

http://www.bigfoothunting.com/info/bigfoot_nocturnal.shtml

http://www.mesacc.edu/dept/d10/asb/origins/primates/day_night.html

http://www.bbc.co.uk/learningzone/clips/different-adaptations-between-nocturnal-and-diurnal-animals/12644.html

http://www.brighthub.com/education/k-12/articles/58019.aspx

www.cal.org/siop/pdfs/nocturnal-vs-diurnal-animals-lesson.pdf

http://library.thinkquest.org/25553/english/interact/lessons/noctlp.shtml

www.seaworld.org/just-for-teachers/lsa/i-014/pdf/9-12.pdf

night vision –

http://www.pbs.org/wgbh/nova/kalahari/nightvision.html

http://dmohankumar.wordpress.com/2010/04/12/night-vision-in-animals/

http://www.news-medical.net/news/2009/04/16/48432.aspx

http://www.webexhibits.org/causesofcolor/17.html

http://www.bigbridge.org/BB14/NIGHT.HTM

http://animal.discovery.com/tv/night/

www.bouldercounty.org/play/recreation/naturedetectives/2004c.pdf

http://www.aoa.org/x6046.xml

http://www.aoa.org/x6035.xml

adaptation –

http://evolution.berkeley.edu/evosite/evo101/IIIE5Adaptation.shtml

https://notes.utk.edu/bio/greenberg.nsf/0/3ee9cccd7c64bffd85256cff0061f4d7?OpenDocument

http://www.nyu.edu/projects/fitch/courses/evolution/html/adaptation.html

http://news.nationalgeographic.com/news/2002/01/0110_020110TVfinches.html

http://www.pbs.org/wgbh/nova/teachers/resources/subj_06_03.html

http://www.nclark.net/Evolution

http://evolution.berkeley.edu/evolibrary/article/evo_31

http://ethemes.missouri.edu/themes/905

http://www.windows2universe.org/teacher_resources/teach_beaks.html

http://serc.carleton.edu/sp/mnstep/activities/35021.html

http://www.teachersdomain.org/resource/tdc02.sci.life.evo.lp_humanevo/

http://www.hhmi.org/biointeractive/activities/pocketmouse.html

http://www.teach-nology.com/teachers/lesson_plans/science/biology/evolution/

http://www.nationalgeographic.com/xpeditions/lessons/17/g35/smcreatecreature.html

Plants That Don’t Sleep Will Take The Dirt Nap

2011-11-22T07:30:00.000-05:00

Biology concepts – nastic movements, turgor pressure, evolutionary pressure, tropism, osmosis

If you don’t let a Mimosa pudica (sensitive plant) plant rest at night, it will wilt away to nothing. A plant that needs a good night’s sleep? Really? We have talked about how sleep revitalizes different brain functions, especially within the hypothalamus (The Best Cure For Insomnia Is To Get A Lot Of Sleep), but plants don’t have a hypothalamus or any brain for that matter. So why does it die if it can't rest; is it out of its mind?

The prayer plant on the left is how it looks during the day, but

on the right, the leaves have folded or curled up. They also stand

straight up, as if at attention. A tough way to spend the night, but

it must serve some purpose.

The prayer plant (Maranta leukoneura) folds up its leaves at night and tilts them upward. When morning comes, the leaves tilt back into their day position and unfold to catch as much sunlight as possible. The folded leaves might look like they are praying (hence the name), and it may appear that they are sleeping, but this is just anthropomorphism.

Humans have a need to feel connected to the rest of Earth’s life, and in the process, we tend to see the behaviors of other organisms in human terms, trying to assign some human motivation to them. So, is the plant sleeping? Does it need to rest? No. Sleep in animals implies inactivity and neural rearrangement, and these don’t occur in plants.

Charles Darwin performed crucial experiments

in plant movement in his later life, including the

identification that chemical signals moving in the

plant are responsible for growth toward the light

(heliotropism). Notice that his son got pretty good

billing as an assistant.

However, the fact that the plant carries out this activity every night suggests that it has evolved in response to some pressure, some need. Surprisingly little is known about why plants move their leaves at night, but there are a few hypotheses. Some scientists believe that changing the angle of the leaves helps funnel dewdrops and overnight rain down the trunk or stem to the roots. Charles Darwin published two books on these plant movements, his theory being that the behavior reduced the chance of chill or freezing.

Another hypothesis suggests that leaves fold up to keep the rain from pooling on them and promoting bacterial or fungal growth. Or perhaps, apposing one leaf closely to the opposite leaf reduces the amount of water lost overnight. However, aquatic plants don’t have to worry about loss of water, but some immersed plants, like Myriophyllum Mattogrossense, still fold up at night. It may be a holdover from their terrestrial days, as most of today’s aquatic plants evolved from terrestrial plants.

My personal favorite proposes that by folding up their leaves, the plants give nocturnal predators a better shot at seeing, hearing, and smelling nocturnal prey. By helping the predators, plants are indirectly protecting themselves from animals that would eat them- plants are sly little devils (more anthropomorphism). It is probable that different plants move for different reasons, so one hypothesis almost certainly won’t cut it for all organisms.

Plants have night moves other than folding leaves. Morning glories (Ipomoea violacea) close their flowers overnight. The reasons for this movement may be a little plainer. Dry pollen sticks to pollinators better than wet pollen, so closing off the stigma to rain or dew keeps the pollen dry. It also takes energy to maintain an open flower; this energy would be best spent when pollinators are around. If the plant’s pollinators are diurnal, they why leave the buffet open all night?

Just as animals have an internal clock, plants gauge

their movements according to the circadian period.

Often plants match their rhythms to pollinator animals

they depend on or to avoid the active periods of

predators. Anyway, I like the picture.

There are also flowers that have the exact opposite behavior, opening their flowers as the sun sets. Philodendron selloum (Is It Hot In Here Or Is It Just My Philodendron) is a classic example, with its spathe closing down in the early morning hours.

Moonflowers (Ipomoea alba) are another example. At about 8:00 pm, the moonflower opens. A single flower can go from completely closed to fully open in less than a minute (http://www.moonlightsys.com/themoon/flower.html). The morning glories and the moonflowers are both of genus Ipomoea, but they have opposite behaviors – different pressures lead to different adaptations, even in closely related species.

These movements of plant structures are independent of the direction of the stimulus, ie. they are not following the sun or being blown by a particularly wind, so they are called nastic movements. Nyctinasty (nyc = night or darkness, nastic = firm or pressed close) is the specific movement of leaves or flowers in a daily pattern, open during the day and closed at night. If directed by the position of a stimulus, the movements are called tropisms (heliotropism, thigmotropism, gravitropism).

The left picture shows that changes in the pulvinus shape could affect the direction of the entire petiole and all the leaves, or individual leaves (like on the sensitive plant). The middle cartoon indicates that filling the central vacuole with water can change the shape of the cell, pushing in one or more directions. The right image shows just how the extensor cells on the bottom must be inflated to lift the petiole, while turgidity in the flexor cells makes the leaf drop.

Nyctinastic movements are accomplished by the flow of water in and out of specific cells in the pulvini (swellings, singular is pulvinus) at the base of the petioles (the stalk that attaches the leaf blade to the stem). It is not unlike our muscle movements in that there is an extensor and a flexor pair. When K+ and Cl- are pumped into the extensor cells on the bottom of the pulvini, they become hypertonic and water follows the ions through osmosis. This causes the extensor cells to swell due to increased turgor pressure.

Turgor pressure refers to the pressure of the cell contents against the cell wall. This increased turgor pressure at the bottom of the petiole pushes the leaf up. In an opposite fashion, night causes a movement of ions to the flexor cells on the top of the petiole. Water flows out of the extensors and into the flexors by osmosis, causing the stem to droop. Flowers and leaves open and close by the same movements, with the extensor and flexor cells located at their bases.

Turgor pressure is the same mechanism which causes the venus flytrap (Dionaea muscipula) to snap closed its jaws of death when an insect disturbs its trigger hairs. These hairs are located on the nectar laden, red lobes of the trap. Touching just one trigger hair doesn’t spring the trap, two must be displaced within 20 seconds of each other. This saves energy and unnecessary trap closings; each trap snaps shut only four or five times, then dies. If you thought the moonflower moved fast, check out the venus flytrap (http://www.youtube.com/watch?v=ymnLpQNyI6g). I’m just surprised we can’t hear the water shooting into the flexor cells!

The venus flytrap supplements its diet of water and carbon

dioxide with proteins from the insects it catches and digests.

The bright surface with nectar draws them in, where they trigger the

mechanosensor hairs. The magnified image on the right shows a

trigger hair with its hinge that transmits a signal to the pulvini to

swell quickly and snap the trap shut.

The trigger hairs are mechanosensors. The stimulus that trips the trigger and causes the flow of ions and water in the extensor and flexor cells of the hinge region is directionally irrelevant; therefore, the snapping shut of the trap can be considered a nastic movement. In this case, as with the sensitive plant (Mimosa pudica), the movement is called haptonasty (hapto = touch).

A small percentage of plants have nyctinastic movements, so they are an exception to the rule that plants don’t move actively, but even a small percentage means that thousands of species do have these movements. This many exceptions underscores the point that nyctinasty must perform an important function.

Just as humans with fatal familial insomnia die from a lack of sleep (An Infectious, Genetic Disease), the sensitive plant has a much shorter lifespan when nyctinasty is prevented. A plant hormone that stimulates leaf opening was identified in 2006. When given to plants continuously, it caused the leaves to remain open. When nyctinasty was prevented in this way, the leaves were noticeably damaged within a few days, and the plant was dead in less than two weeks. It may not be sleep, but whatever it is, it is just as important.

Some plants are open during the day and some are open at night, just as some animals are active during the day and some during the night. And just as plants adapt to a time schedule to promote survival, animal adaptations are crucial to life in the light or the dark. But that doesn’t mean that some organisms won’t throw us a curve, as we will discover next time.

Ueda, M. and Y. Nakamura. 2006. Metabolites involved in plant movement and ‘memory’: nyctinasty of legumes and trap movement in the Venus flytrap. Natural Product Reports, 23 (4): 548-557.

For more information, classroom activities or laboratories on nastic movements or turgor pressure, see:

nastic movements –

http://plantsinmotion.bio.indiana.edu/plantmotion/movements/nastic/nastic.html

http://sci-wikibook.bacs.uq.edu.au/?q=content/8-2-5-nastic-movements

http://www.biologie.uni-hamburg.de/b-online/e32/32.htm

http://www.tiem.utk.edu/~gross/bioed/webmodules/nasticmovements.html

http://dennis-holley.suite101.com/nastic-movements-in-plants-a129827

http://seedsaside.wordpress.com/2007/02/18/word-of-the-week-nyctinasty/

http://abstracts.aspb.org/pb2011/public/P19/P19066.html

http://amirshahrokhi.christopherconnock.com/tag/haptonasty/

http://bottleworld.net/?p=38

http://www.wiziq.com/tutorial/33908-2-How-Plants-grow-and-move