Talking Turkey

This being the holiday season, it seems appropriate that I break my two-week silence with something seasonal.  How about turkeys?  They are strange, interesting and mostly unknown to us except as a difficult cooking challenge in late November.

First, a little trivia:  turkeys have different names depending on their gender and their age.  Try to match the name to the type of turkey.  Answers are at the bottom of this post.

1. Gobbler	a. Female adult
2. Jake	b. Male adult
3. Tom	c. Hatchling
4. Poult	d. Young male
5. Hen	e. Male adult (Yes, there are 2 of these.)

Before this spring, the most I knew about turkeys was how to cook one and that Ben Franklin thought they'd be a better choice for our national bird than the bald eagle.  Then one day, on a early spring hike, I got sucked in to the turkey world.  My husband and I both heard a peculiar cackling sound up ahead of us, and as we hiked nearer, the sounds became quite loud.  We easily located the sounds' sources: two tom turkeys up in two trees gobbling back and forth at each other, apparently arguing over who would be a better mate for the next female turkey that should happen along.  The turkeys displayed their stereotypical puffed-up colorful chest and tail feathers, looking like Liberace versus Porter Wagoner. 

My husband quickly figured out that the toms were as willing to gobble at him as they were to gobble at each other.  He had a rather long conversation with the toms, which got more interesting when the husband of another hiking couple joined in too.  What is it with guys and turkey noises?

Non-agitated foraging turkey toms.  (Photo by C. Sams)

It turns out that adult male turkeys spend a rather large percentage of their time agitated - either arguing with other males or trying to impress females.  When agitated, they puff up all their feathers and their featherless head skin rapidly changes colors from red to white to blue.  They also have erectile tissue on their faces (of all places!) that stands at attention when they are attempting to attract a mate.  All turkeys have extra flaps of tissue on their faces, but males have the snood (the fore-mentioned face penis), the wattle (hanging under the beak) and the dewlap (webbing connecting the chin to the neck), in addition to caruncles (warty growths on all adult turkeys).  Female turkeys are drab, less warty and less bald - though much more handsome than they sound from this description.

Domesticated turkeys are the same species as the wild turkey, but they have been selected for white feathers, extreme muscle mass, and quick growth.  Domesticated turkeys are so overgrown that it is physically impossible for a male turkey to copulate with a female turkey, and all domesticated turkeys must be artificially inseminated (there's a career for you!).  It is also nearly impossible for domesticated turkeys to fly after adolescence, as they are weighted down by their big, juicy light and dark meat.

Turkeys are social animals, and they will forage for food and hunt for mates in groups when given the chance.  Farmed turkeys grow better and faster when allowed to be near other turkeys.  But when grown with thousands of other turkeys in close conditions, as is the case with the standard large turkey barns, their social behaviors can lead to odd and grisly problems.  Any turkey with the slightest wound to its head will be quickly pecked to death by the other turkeys around it.  A single male turkey in a barn of all females will suffer a similar fate.  A female in a male barn will be trampled by the males attempting to mate.  Strange.  Turkeys are gender segregated and often have their beaks trimmed to reduce economic loss from turkey attacks.

Like the chicken, turkeys have light meat on their breasts and wings, since these muscles are less used by these non-flying birds.  The standing muscles in their legs are used constantly, so they are the dark meat. 

Light and dark meat a few seconds before being eaten.

There tends to be more fat stored in the turkeys' legs, which makes dark meat richer and moister in a cooked bird.  Turkeys are notorious for drying out as they cook because they take a LONG time to cook (much longer than you think).  Since they have so much more muscle mass than chickens, by the time heat from a cooking oven has reached the center of the bird, the outside of the bird has had all its moisture evaporated, becoming stringy and dry.  This problem is made worse by cooking a turkey with stuffing inside the body cavity.  When the bird is stuffed, it basically becomes a big ball of food that can only be cooked from the outside in.  The stuffing often is not cooked thoroughly and can carry salmonella (as my poor cousin discovered the first time she hosted the entire family for Thanksgiving).  Without stuffing, air from the oven can bring heat inside the bird, and the meat cooks from the outside in as well as the inside out.  When the cook bastes the turkey (pours the turkey cooking juices over the cooking turkey) a few times during the cooking process, the white meat can retain more moisture.  The cook can also cook the turkey at a lower temperature for longer to keep the surface of the bird from drying out.  Of course, there's always gravy.

Basting the turkey to keep the light meat moist.

Wild turkeys were over-hunted in the early 1900's, and they were nearly extirpated from North America.  Today their numbers have much improved, and there are enough turkeys to allow hunting in most states.  Estimates of the wild turkey population size in the US are around 7 million birds.  Wild turkeys are vastly outnumbered by their domesticated cousins, as the US produced around 248 million turkeys last year.  That's almost one turkey per person!

Congratulations on sticking with the turkey post.  You will be rewarded with answers to the quiz from the beginning of this post.  Hens are adult females.  Gobblers and toms are adult males.  Jakes are young males.  Poults are hatchlings (which are unusually able to run around and feed very quickly after hatching). 

I promise it won't be as long until the next post.  We'll get back to plants next time. 

Leopard, Contained

Today I watched a leopard pace in its tiny cage.  Male leopards are used to 30 square miles of home range, and this one was lucky to have 30 square yards.  This subspecies of leopard, the Amur leopard, is critically endangered in the wild, and the zoo is participating in a conservation program that likely helps to maintain biodiversity so the species doesn't go extinct.  Nevertheless, this leopard was pacing.  There was a clear path worn in the grass, and he was bored.

Amur Leopard, Panthera pardus orientalis.

Leopards are often confused with jaguars and cheetahs, but once you look carefully at their spots, you won't confuse them again.  Leopards have hollow spots, called rosettes.  Jaguars' rosettes have little black spots inside each one.  Cheetahs have solid spots.  Leopards are the largest and stockiest of the three, with large males tipping the scales at 200 pounds, though most are smaller.

Notice the empty rosettes that indicate this is a leopard, not a jaguar.

Leopards' biggest difference from other big cats is a behavioral characteristic.  They are generalist carnivores.  They will eat anything from the size of a dung beetle to a 2000 pound male eland, as long as it is in the Animal Kingdom.  They prefer prey in the 44 pound - 175 pound range, which is a bit disconcerting for a species with most of its members in the preferred prey size range.  Leopards could take humans for prey easily - their range overlaps with humans, they are well camouflaged, and they can hide around human settlements.  For some reason, leopards don't choose to take humans - they hunt all other animals preferentially.  A few leopards that were injured or sick have taken humans as prey in the past, and once they started, they kept doing it until they were killed.

As explained in a previous post, generalist predators tend to have more intellectual capacity than predators that don't have to make as many decisions or learn about as many different types of prey.  Leopards hunt alone, which means they are unlikely to evolve complex social interactions, which is likely cold comfort to their prey.  Leopards are definitely stronger than other big cats of similar size, and they have been observed hauling prey up to three times their weight high up into trees to save for a later meal.  This combination of strength and intelligence makes the leopard particularly awe-inducing to me. 

The highlight of our leopard-watching for the day was a dangerous game between the leopard and a squirrel, two smart-cookie generalist consumers.  The squirrel had found a prized piece of hot dog bun near the leopard cage and was trying to decide whether to eat it in place or carry it away to another location, a vegetarian version of the leopard's prey-stashing.  The leopard heard the leaves rustling around the squirrel, crouched, sighted the squirrel and pounced.  The leopard was denied its afternoon snack by only a thin wire fence.  The squirrel continued to appear to frolic in the leaves, rustling them unnecessarily along the edge of the cage for another minute or two before it left to gorge on simple carbs.  The leopard was as agitated as a house cat being teased with crinkly paper.  It struck me that the squirrel had learned the fence would hold and ignored the deadly but contained predator.  The leopard had not completely habituated to the fence and continued to respond to temptations on the other side.  It either hadn't learned the fence was immutable or its brain was so exquisitely tuned to the rustling prey sounds that there was no other possible behavioral response the leopard could offer at the moment.  If you have ever played with  house cat, it certainly seems that they are compelled to pounce on rustling things - perhaps it is the same with big cats.

Leopard focused on a squirrel just two feet away.

Turnips

Turnips are ridiculously under-appreciated.  They are the easiest vegetable to grow.  They are marvelously delicious.  They produce anti-cancer compounds and their nutritional profile is similar to broccoli even though they look more like potatoes.  Their greens are the richest-tasting greens of all cooking greens.  To top it all off, they are in my favorite vegetable genus, Brassica.

The picture below is of an enormous purple turnip at the Chicago Botanic Garden, a fabulous botanic garden with an extensive fall vegetable section.  This turnip is pure white on the inside (I assume - I didn't cut it open), and it should also be white below the soil.  Sunlight causes the root epidermal cells to become pigmented in this variety of turnip.  The pigment seen here is an anthocyanin, but some turnips have a green suntan from chlorophyll production. 

A gigantic turnip!

The turnip in the portrait above, since it's very large and pigmented, is likely to have some zip to its flavor, much like a radish.  The greens will be piquant as well, like mustard greens.  The root would be delicious cooked in a stew with other vegetables, and the greens could be tamed by throwing out the first round of steaming or boiling water if necessary. 

My favorite turnips are Hakurei turnips, which are pure white regardless of sun exposure, smaller, and not hot.  They are sweet and fruity and even the greens can be eaten raw.  You can find them at farmers' markets in the fall and spring.  Their texture is divine when cooked - smooth and silky, and I like them sauteed or cooked into soups.  It's absurd to think of eating turnips without the greens in my book, so I always get the roots cooking while I prep the greens.  Then I cook the greens with the roots for the last few minutes for a great combination of flavors and textures.  YUM.

Turnip and greens, Brassica rapa.

 To grow turnips, just sow a thick line of seeds and cover them with a little soil.  As the turnips grow, you can thin the young plants by collecting some greens before the roots start to fill out.  In just a few weeks the turnip roots will grow and you can harvest them as you need them for several weeks.

Turnips and butterhead lettuce.

Turnips are members of the genus Brassica, which is a group of unassuming weedy-looking plants with fast growth rates and fantastic variation in growth forms.  Each brassica species modifies a different plant part to store energy, usually in response to humans breeding the plants to make agricultural varieties.  Turnips store energy in their roots (as do rutabagas), and the rest of the plant looks pretty normal.  Other brassicas put lots of energy into leaves (cabbage and kale), leaf stems (bok choi, seen below), flower buds and stems (broccoli and cauliflower), leaf buds (Brussels sprouts, seen below), stems (kohlrabi), and seeds (canola, mustard).  It's fascinating to me that these plants are so closely related with such striking similarities in leaf and flower structures but with such vast differences in other plant parts.

Brussels sprouts, Brassica oleracea var. gemmifera.

Bok choi, Brassica chinensis.

Brassicas generally are quite nutritious and low in calories.  Consuming these vegetables regularly appears to have a protective effect against many cancers, though the mechanism is not well understood.  For optimal amounts of the cancer-fighting compounds, eat these vegetables raw or lightly steamed, not cooked into oblivion.  Some brassicas contain bitter compounds detectable by a subset of the human population.  These people can't enjoy the wonderful flavors of brassicas because they find them to be too bitter.  Also, children are better at tasting bitter compounds than adults, which explains why they more commonly dislike vegetables. 

Consciousness

I just finished a completely fascinating book about what scientists think about the human brain.  It's called Incognito: The Secret Lives of the Brain, written by David Eagleman, a neuroscientist at Baylor College of Medicine.  The book summarizes the latest ways of conceiving of and explaining the functions of the human brain.  It's a completely captivating science book and manages to also be a quick, easy read - I recommend it to everyone who has a brain.

Among neuroscientists, there is considerable debate about what consciousness is and whether other animals have it.  Dr. Eagleman wrote a compelling explanation about why humans have consciousness and who else might have it.  To explain, I'll need to start with a little background.

Animals have nervous tissue, the tissue for communicating information from one area of the body to another.  For animals like this scud, the nervous system is composed of a few neurons (cells) that can sense and carry information, as best we can tell.  The information carried in these neurons appears to be simple, like "there is more salt in the water ahead".

Scud captured in pond water (40x magnification)

It's impossible for humans to know what it feels like to be a scud, but people who study scuds are almost certain they are not conscious.  Scuds show evidence of a what Eagleman describes as modules or programs for conducting specific behaviors.  In the scud, such modules would be genetically programmed behaviors such as "swim away from the light" and "chew on rotten organic matter".  The scuds don't have choices, and they can't modify their behavior - each behavior is either done or it isn't, and there is a clear way of prioritizing behaviors so the scud doesn't have to think about it (because it can't think).

Organisms with a wider variety of behaviors have many modules for solving problems.  For example, a squirrel can eat many types of foods, and they can search for foods in many ways.  Consciousness starts to become necessary as a way of deciding which program to run in which circumstance.  Squirrels may have rudimentary consciousness, since they can choose to hunt acorns or raid the bird feeder.  Nevertheless, squirrels don't seem to be able to recognize themselves in mirrors or solve math problems.

A fat squirrel peeking out from behind a tree in Lincoln Park.

The more redundancy and plasticity in behavior types a species has, the greater the need for consciousness.  Humans have enormous behavioral variety, so we need consciousness to figure out which behaviors we're going to do when (should I hunt for food at Trader Joe's or Dominicks?).

Eagleman also points out that just because we have consciousness, doesn't mean we need to use it very often.  For activities we have learned, we have committed those skills to the comparably vaster unconscious part of our brain.  Have you ever driven across town then wondered how you managed to get there since you don't remember any stop lights or roads?  That wouldn't happen if you were driving a new route.  The apparent amnesia is a sign that you have learned the route so well your unconscious brain can handle it and let your conscious brain do other things, like learn a new song on the radio or talk to your mom on the phone.  If the routine deviates from normal, for example if a car swerves in front of you or there is a blocked road, your conscious brain takes over and figures out what to do - and you don't forget to tell your friends about the road block or near accident. 

Conscious activities are usually new activities.  When you are learning something new and doing something new, you notice so much more about the world, and time seems to go more slowly, since there is a lot more 'happening' in a conscious period of time.  Unconscious activities, like being zoned out while jogging or working or chopping onions, etc., kill a lot of time quickly without you noticing it has passed.  So the trick to getting through boring activities like waiting in line is either to zone out somehow or to turn it into a new experience.  If you want to slow down time and live a longer life (at least a seemingly longer one), have a wider variety of experiences.

Eagleman claims there are degrees of consciousness, which makes me wonder what consciousness would be like if I had an even more complex brain.

Of Birds and Meat

I saw two birds yesterday.  One was standing on the pavement next to Lake Michigan, and the other was chopped into bits in a pan in my kitchen (also next to Lake Michigan).

Inland gull hanging out in my town.

Chicken hanging out in my kitchen.

The first bird is a type I see nearly every day as I'm walking around town.  I know it's a type of seagull, though I don't know which type (never was a birder).  Seagulls are found anywhere there's water, not just at the ocean.  When they are found away from the ocean, they're often called inland gulls.  Seagulls are regarded as pest birds by some, but I love them.  They are great scavengers, and this gull no doubt is helping to keep our lake shore clean of all kinds of technically edible trash.  Seagulls are incredible fliers.  I watched one fly during the giant storm last week with gusts of wind up to 60mph, and it was doing just fine.  Since gulls are strong fliers, it means their wing muscles are strong, tough and dark in color (more on this in a minute).

All we have of the second bird to compare it to the first is its wing muscles.  Chicken's wing muscles (not the actual wings, but the breast meat - the part that actually pulls on the wings) are giant by comparison to the gull's, but despite their size, they are weak, flaccid and white.  Chickens don't use their wings, really.  Commercial chickens have been bred to have giant breast muscles, since that's the most commercially profitable part to sell in the US.   Chickens don't fly a lot when they have access to the sky, but when kept in confinement as they grow in a factory, they can't fly at all.  

The white color of commercial chicken breast meat arises from a combination of factors.  First, the genetic characteristic of chickens being more walking birds than flying birds means that their wings aren't adapted to being strong.  Secondly, these birds'  enforced lifestyle is one of all standing or sitting and no flying.  Muscles adapted to working hard, and muscles that are exercised are usually darker in color, most apparent in poultry meat.  Dark meat's color comes from its large quantities of a reddish-brown-pigmented molecule called myoglobin.  Myoglobin does the same thing as hemoglobin (the dark red protein found in the blood), but it is found in the muscles.  Hemoglobin and myoglobin both hold oxygen from the air we have breathed in.  For muscles that work harder and at fast speeds, the need for oxygen is intense.  Having myoglobin present to store extra oxygen means that muscles can work harder and faster.  Muscles can genetically have more myoglobin in them, and the quantity of myoglobin increases with increased muscle usage.

Though I have never eaten or dissected an inland gull, it would probably have dark breast meat, since it uses its wing muscles so much.  If you have ever eaten duck breast, you may have noticed that it was very dark - because ducks are good fliers.  Duck leg meat is usually lighter than the breast meat.

Time for lunch?

Gorilla Feet

I promise every post in Chicago won't be about the apes at the zoo, but there will probably be a few more after this one too!

This is a gorilla foot:

Gorilla Foot

I was able to get such a great picture because the gorilla was sleeping with his foot up on the glass.  I touched the glass after I took this pictures, and it appeared to be about 1.5 inches thick.  After seeing the adult male gorilla kick the door in his enclosure a few days ago, I'm hoping that glass is thick enough!  That gorilla is massive and extremely strong. 

Gorillas are usually fairly mellow, and they seem to have less intense social interactions than chimpanzees do.  They do engage in grooming behavior, aggression and play, but their interactions are much less constant than the chimpanzees'.  They are vegetarian, mostly forest floor dwelling and less active in general than chimps.

Gorilla's forelimbs are massive and long.  Their arms are about six times stronger than ours.  Their legs are much smaller, though still strong.  Even though they spend lots of time on the forest floor, they are still very good climbers, and they use their arms to amble around the branches and vines with ease. 

Gorilla's feet have opposable thumbs.  They are good at grasping things - branches or food, but they are not good at walking upright.  Our feet have all toes pointing forward, which is great for bipedal locomotion, but have you ever tried to pick up anything with your toes?  Not easy.

Beyond shape, there are many similarities in our feet and gorillas'.  First, scroll back up to the picture and notice the prints.  I can't call them fingerprints, because they are on the sole of the foot, but we have these too.  We have prints all over the bottom sides of our fingers, palms, toes and soles, and so do gorillas.  These prints are due to ridges in the subskin (dermis) where it attaches to the upper skin (epidermis).  The ridges and valleys allow for more contact between the two layers, which reduces separation of the layers from friction.  What that means in everyday English is that it reduces the incidence of blisters.   

Next, notice the nails.  These guys have fingernails and toenails, not claws.  Nails are good for manipulation of plants and small structures, and they protect the fingers from stomping or insect bites, but they're not good for ripping flesh.  Since gorillas are herbivores and big and strong, they don't need claws for food or defense, so they have nails.  We are not entirely herbivores, but we use tools to catch our animal prey, so we don't really need claws either.  We do, however, need to manipulate small items, and nails are useful for that.

Gorilla and human feet are homologous structures, meaning they have the same evolutionary origin, and have developed from the same bone and muscle pattern.  Since gorillas and humans separated on the evolutionary tree a long time ago (well, in evolutionary time, not so long ago) and have adapted to different environments, our feet have evolved in slightly different directions too.  Scientists think the evolutionary ancestral foot to humans and gorillas was more like the gorilla one, though probably smaller and more hand-like.  Primate ancestors were even less bipedal and more tree-dwelling. 

Zoos and Conservation

The Lincoln Park Zoo is on my daily walking route now.  It's free and open to the public, and I can power walk right through or linger and marvel, depending on how I'm feeling and what the animals are up to.  It's a small zoo, but the construction of several of the animals' enclosures allow for jarringly intimate observations of the animals.

The gorillas and chimpanzees, in particular, are housed in such well-designed pens that I find myself moved and astonished by them as has not occurred in other zoo experiences.  The floors are elevated so the monkeys eyes are level with mine and the high-quality non-distorting glass allows a 1" distance between my skin and theirs.  I can see subtle changes in facial expression, lines in the soles of their feet, and individual hairs between the fingers of grooming chimps. 

A chimp comforting another after she was refused food by a male.

The resemblance in anatomy, emotion and behavior to humans makes these animals more interesting to watch than any other in the zoo.  Their enclosure is interesting enough that they seem to feel comfortable exhibiting a variety of the complex behaviors I have read about in Jane Goodall's accounts.  They groom each other, ask for food, diffuse conflicts, climb, play and interact with their surroundings.  It is difficult not to assume one understands their motivations and behaviors, since they look so much like us.

I watched this chimp make a nest of burlap sacks, try it out several times, readjust the burlap then roll over and suck her toes.

After awe and utter fascination, the strongest sentiment I have when watching these creatures is how unfair it is that they are put on display in fancy prison cells.  They clearly have lesser environments than they would in the wild.  Their behaviors and free expression are constricted.  They are aware of the constant stream of eyes looking at them.  The big silverback gorillas protest their enclosure by sitting with their backs always to the glass.  The animals are not happy about being enclosed.  I always imagine some more powerful aliens coming to earth and capturing a few of us for their zoos at home.  We would be outraged.

And yet, there is some considerable benefit to animals in zoos from a conservation perspective.  Zoos create opportunities for the development of strong affection of humans for animals, making us care about their continued presence on earth.  We are more likely to push for the conservation of chimpanzee habitat after experiencing reverence for them in a zoo.  In the worst case scenario, zoos have been the last refuge for species that are almost extinct.  The black-footed ferret once existed solely in zoos and has been reintroduced into wild land.  Zoos also provide the means for maintenance of genetic biodiversity, by shipping sperm or arranging for matings, so that a species has a wider variety of genetic combinations, reducing the likelihood of extinction.

If it were up to me to decide to free all the animals in zoos or keep them, I would be strongly conflicted.  Clearly it unethical to keep socially complex animals in tiny, uninteresting enclosures.  As zoos expand and enrich their animals' habitats, the balance shifts more toward the value of zoos, especially since humans will apparently destroy all natural habitats without education and enforcement of the alternative.  Zoos are an imperfect solution, but it seems that at least some zoos are necessary in our current world.  I know I'm going to spend a lot of time in the ape house at our zoo while I'm in Chicago, but my amazement will always be tinged with pity.

A Love Letter to A. P. Environmental Science Students

It's getting close to Halloween, and the scariest thing for most APES students is the nitrogen cycle, so why don't we tackle that today.  The dreaded nitrogen cycle strikes fear into the hearts of Environmental Science students everywhere because it's so difficult and so necessary to know.  But just like vampires, mummies and werewolves, it gets more interesting the more you understand it (though it still might scare the you-know-what out of you!).  Don't fear - you can do this!

Do you know why I put a picture of this Chicago bean tree (actually a honey locust) here?

First of all: what is nitrogen and why do we care so much about it?  Living things on earth are mostly made of the atoms carbon, hydrogen and oxygen, but proteins need a little nitrogen.  No living thing can live without proteins, therefore nitrogen is necessary for life.  Nitrogen, however, is in short supply, at least in a usable form.  If you think of atoms like Legos, each atom would be a different type of Lego.  Atoms can bond together to make larger structures like proteins, carbohydrates, DNA and oils, which then add up to whole organisms, just like Legos can be put together to make bigger things.  Nitrogen atoms are the special Lego pieces that are rare but that you can't build anything without.  Animals get all their nitrogen from eating protein in food.  When you eat food, your body takes apart the food's Legos (atoms) so that it can put them back together again into the molecules you need (or your body burns the Legos for energy, but the analogy kind of breaks down there).

Usable form?  Take a big, deep breath - it will help calm you down, plus it demonstrates the next concept.  What you just inhaled (air, hopefully) is 78% nitrogen.  OK, exhale.  You just exhaled every bit of nitrogen that you had inhaled, absorbing none of it.  Nitrogen in the air is in the form of N2 (I don't have subscript), or two nitrogen atoms double-bonded to each other.  There is actually a triple covalent bond holding two nitrogen atoms together in N2, which makes them nearly impossible to get apart.  Think of identical Lego pieces so hopelessly stuck together that you have to go get a kitchen knife to separate them.  Your lungs don't have the biological equivalent kitchen knives, so they can't break apart the nitrogen atoms to use them, and all the nitrogen you inhale is useless to you (except that it makes our atmosphere very stable).

The Kitchen Knife Monopoly:  Nature runs a tight kitchen, and it won't let you play with knives.  Only specific soil bacteria are allowed to have knives.  By which I mean only bacteria can fix nitrogen from it's stuck form to separate, useful atoms.  The separate atoms are quickly bonded to hydrogens to make ammonia (NH3).  The name of this process is nitrogen fixation.  It is thought that the ability to fix nitrogen evolved once on this planet when bacteria were pretty much the only critters here.  Everyone else after that found that it was easier to trade with bacteria than to evolve their own way of fixing nitrogen.  It is extremely difficult to fix nitrogen because a lot of energy is required to break the triple bond between two nitrogen atoms.  Bacteria expend a lot of ATP to break the nitrogen, but no one else is going to do it for them, so they just get on with it.

Wheeling and Dealing:  Anyone else who wants fixed nitrogen has to get it from bacteria.  They can wait for the bacteria's waste and absorb that straight from the soil in the form of ammonia, but bacteria aren't very wasteful, and there isn't much nitrogen available this way.  Some organisms have found a better way to get nitrogen: they can strike a deal with the soil bacteria.  Many plants, especially legume-type plants, have a mutualistic symbiosis with the soil bacteria.  Plants provide the ATP and some oxygen in exchange for lots of ammonia.  Legumes even provide specialized little lumps (nodules) on their roots to house the bacteria. 

What About Us?  As I said earlier, we get all our nitrogen from food.  We need protein in our diet because of the nitrogen in protein.  Think of foods that are high in protein.  Did you say meat and eggs?  You're right, but think of vegetarian foods that are high in protein.  Hopefully you said beans, peanut butter and tofu.  When you think about it, you realize that all these foods are legume-type plants, which makes sense because legumes are able to get more nitrogen from housing nitrogen-fixing bacteria in their roots.

Random picture of black beans!

But that's not all is it?  Sorry, no.  When we learn about Environmental Science, we always learn about the full cycle of things - externalities, life-cycle costs, recycling, etc.  We have to finish the story.

Energy From Nitrogen?  Since it takes so much energy to break N2 apart (a reduction reaction for you chemistry folks), it would follow that energy can be had from getting those two nitrogens back together.  In fact, that's just what TNT and fertilizer bombs do is allow a large quantity of nitrogens to reunite - boom!  Bacteria in the soil can take advantage of single-nitrogen molecules and get some energy from oxidizing them in two different ways.  The first way is called nitrification, in which bacteria take ammonia molecules and make nitrite, then nitrate ions for energy.  Extra nitrate ions left in the soil from this process are very easy for plants to absorb and use.  You can think of this as half-oxidizing the nitrogens (sorry, chemistry teachers), and releasing some of the available energy.  Fully oxidizing two nitrogen compounds results in the production of N2, releasing more energy and returning the nitrogen to that useless gas molecule in the atmosphere.  (We just came full circle!)

Still Not Done:  It helps to know the following trivia about the nitrogen cycle too.  (1) Animal waste and dead organisms contain a lot of nitrogen.  Soil bacteria break down that waste and release the nitrogen into the soil as ammonia (in a process called ammonification), which is available for plants to use.  You may have noticed this if you have a dog that pees in spots around the yard that result in greener grass patches.  If your dog always pees in the same spot, you no doubt notice that too much ammonia is toxic.  (2) Agriculture results in nitrogen being absorbed from the soil into plants, then plants being carted away to markets, along with the soil nitrogen (where did all the good Legos go?).  Soil nitrogen must be replenished with chemical fertilizer, manure, growth of legumes or other fertilizer.  (3) Too much nitrogen in a body of water, say from fertilizer runoff or sewage overflows, can cause the plants to overgrow, choke out the sunlight and cause lower-down organisms to die, decompose and use up all the oxygen.  Then everything else in the water suffocates and dies.  This is called eutrophication and is worth understanding very solidly.  (4) Some single-nitrogen compounds can be made from the energy of lightning separating N2 molecules.  Also, humans use the Haber Process the break the N2 bonds to make ammonia for making bombs and fertilizer.  The Haber process uses lots of energy to split the N2.  It uses N2 from the air but gets hydrogens from natural gas (CH4), so making fertilizer is a very fossil-fuel-intensive process.

Decisions, Decisions

As I was walking on my new daily exercise route in Chicago (up Lake Michigan's shore and down through Lincoln Park and the zoo - tough, I know), I almost stepped on these two mating cicadas.  They made me ponder the behavioral decision-making processes in animals. 

Two-headed cicada!

I'll start with the assumption that behaviors exhibited by animals are generally the result of a long evolutionary history, with a little improvisation and chance thrown in here and there.  This means that behaviors exhibited by animals are ones that caused their ancestors to have more offspring and pass on the traits for exhibiting those behaviors to their offspring (thanks, Charles Darwin).

Clearly the mating behavior I observed in the cicadas is necessary for the production of offspring and passing on genes to the next generation.  However, the fact that the cicadas were mating in the middle of a well-traveled concrete pathway would seem to be counterproductive in the Darwinian struggle for progeny.  Cicadas as a species are probably in the middle of a subtle evolutionary shift wherein those cicadas that mate on tree branches and in grass survive more often than those that mate on concrete.  How genes could be involved in that particular behavior, I don't know.  But I do know that fairly complex behaviors have genetic components.  For example, type of tree branch used for nest site choice in birds can be genetic. 

Obviously the cicadas were incapable of the complex thought process needed to see that mating on a sidewalk would get them both squished and that they should just move 6 inches to the left into the grass.  Animals are not thought to behave rationally.  That means they don't weigh the pluses and minuses of behavioral choices - they just act.  This always brings me to the following questions:  If animals don't actually decide what they are going to do, why do they do anything at all?  And how do they know what they should be doing?

For behaviors to evolve, there has to be a way for animals to 'know' that they are choosing a good behavior versus a bad behavior.  There must be something similar to pleasure and pain to reinforce good and bad choices.  In fact, the hormone that causes pleasure and contentment in humans (oxytocin) has been found in animals.  Animals also have adrenaline rushes, which elicit fear, panic and aggression in humans. 

Unfortunately, there is no way to know what an animal actually feels, so we must come to conclusions by analogy.  If oxytocin is released, the animal must feel something positive - perhaps calming or pleasurable, because that's how it works in people; if adrenaline is released, it must be the equivalent of scared, etc.  An animal that feels pleasure when it swallows food, drinks water, mates and finds safe locations to rest will probably survive.  An animal that feels fear when a larger, unfamiliar animal is near will respond by running away or fighting, both of which can extend life span. 

My favorite example of how this might work involves a study of my least favorite organism: roaches.  In a study to mimic roach behavior, scientists programmed tiny, roach-shaped robots to be still when they are in dark places and near other roaches and to run fast when they were in the light.  With this simple behavioral program, the roaches ended up behaving almost identically to real roaches.  I imagine that in real roaches' ganglia (little clusters of nerves throughout their bodies that act like little brains), they feel roach-y contentment in dark, tight spaces with buddies around, and they feel panic when the lights come on.  Oddly enough, in a test to see if roaches have a stronger preference for darkness or being around their roach pals, they chose the social environment over the safe environment.  Who knew roaches were such followers? More. 

There must be at least a few cicadas out there with a mutation that makes them fear stepping on concrete and therefore move away quickly when they find themselves on it.  The concrete-fear gene should confer an advantage to those cicadas, as they would be less likely to be scraped out of the treads of a tennis shoe one day.  Assuming humans keep building and using concrete sidewalks, some day all the genes for sidewalk-mating will have been eliminated, and only the concrete-fearing cicadas will have survived.  Cicadas as a species will be smarter, all without a single cicada having to think an actual thought.

Of course, humans always make their decisions based on cold rationality, because we have the ability to think and separate our emotions from our thoughts.  We have evolved brains capable of weighing our options and choosing the best path, so we don't need instinctual behaviors.  ...Not so fast!  We have plenty of positively- and negatively- reinforced behaviors: pleasure for eating, playing, making a home and mating, and pain from loss, fighting and overwork.  Humans have repeatedly been shown to act irrationally in less obviously evolutionary ways too.  Some of us take unnecessary risks, get pregnant too young or fall in love with the wrong person.  We have even learned that the average of millions of human decisions is not based on rational principles, as it is impossible to explain or predict the stock markets. 

We must be careful not to fall into the trap of assuming humans are so different from other animals.  There are evolutionary payoffs to many irrational behaviors.  Risk-taking can result in big rewards in status and resources, and perhaps more mates to pass on risk-taking behaviors.  Teen pregnancies tend to pass on genes early and often (not that I'm advocating teen pregnancy).  Romantic decisions are made at least sometimes based on evolved chemical signals (pheromones and antibodies) that might signal compatibility and more healthy offspring.  Human social tendencies can lead to careless financial decisions just as roach social tendencies can draw roaches into unsafe locations. 

So how much of our behavior is instinct and how much is logic? 

Green Lacewing: Teenage Hellion

The common green lacewing, Chrysoperla sp., is a welcome insect in my garden and on the farm, but it sometimes reminds me of Dr. Jeckyll and Mr. Hyde.  It has rather alarming personality shifts.   It starts and ends life with delicate, gentle beauty, but it has a dramatic personality change during its ferocious adolescent stage.  

Green Lacewing Eggs

The miniscule space needles growing out of the shefflera stem above are not fungi.  They are the slim, stalked eggs of the green lacewing.  Lacewing eggs are usually laid on the undersides of leaves and stems.  They are a lovely surprise to find when working in the garden.  They seem so fragile that they would break or bend in the breeze, but you can brush your finger against them and they stand back up.  They are so delicate, that I can't feel them, even with my less calloused ring fingers.  They stand in peaceful beauty, glistening in the sun, while their infant lacewings develop inside each egg.  

Watch out, because after a few days, each egg cracks, and out charges a fierce, anxious monster of a teenage insect: the green lacewing larva.  It moves quickly and ranges widely, and it is hungry for fresh meat. It stalks, catches and eats every insect it can catch with its pointy mouth parts.  It kills its prey with toxic venom.  If it were 100 times larger, you would have to fortify your house and never go outside!  I'm certain some dangerous movie aliens are based on these ravenous killers. 

Scary green lacewing larva, source in picture.

After a few weeks, the green lacewing larva begins to feel full.  Its hunger for protein is sated.  It's ready to settle down, take up a peaceful existence and devote itself to future generations.  It finds a sheltered space under a leaf, wraps itself into a silk-bound ball, and metamorphoses into an adult.  The adult emerges, green and shimmering, and spreads its delicate, reticulated wings.  It floats off into the night, sipping nectar, mating and laying eggs.

Green lacewing adult with outstretched right forewing.

Don't fear the lacewing, even in its carnivorous stage.  It won't bite or sting you.  It will, however, remove hundreds of pest insects from your garden.  One lacewing larva can eat 200 aphids in a week!  Some organic gardeners buy and release lacewings onto their farms to help control insects.  Pesticides kill these useful farm workers, allowing pest insects to move back into the area with no predators.  Since pests can usually reproduce faster than prey, if both pests and prey are killed, you're likely to have a worse pest problem in a few weeks when the population recovers.  Encouraging beneficial insects like the green lacewing helps cut down on expenses, work and pesticide usage.  To encourage lacewings, plant flowers that the adults like, for example coreopsis, dill, Queen Anne's lace, cosmos and other similar plans.  You can also leave some of your dandelion weeds, because lacewings love them.

I apologize to my biologist readers for all the anthropomorphizing above, but these little critters seem very dramatic to me. 

Little Green Farm Workers

With the greens of the farm plants fading, two bright green animals brought themselves to our attention on the farm this week.  Both of them are welcome creatures that help us keep the numbers of pest insects low. 

The first green creature of the week, a rough green snake, was hanging out in the barn.  I found him in a basket I was about to use for eggplants.  We quickly caught him and put him in this jar (with air holes), so that the farm owner's son could see him too.  These little green snakes are a rare sight on the farm, and they hold a special place in the hearts of this farm family.  We marveled and the bright emerald luminescent color of this sleek, friendly snake.

Rough Green Snake with grass- we released him quickly!

Rough green snakes don't get large.  They can grow to almost 3 feet long, but they always stay skinny.  They are great climbers and spend their time hunting insects and spiders in any kind of vegetation from grass to trees, but they prefer to be higher up rather than on the ground.  Green snakes are well camouflaged for their preferred habitat, and I've probably seen dozens of them without realizing it.  They coil up in branches to sleep at night, and in the cooler weather, they seek refuge under logs or other debris.  This may be why our green snake ventured into the barn.  He probably thought he found a good place to overwinter.

Later in the week, we were working in the greenhouse, and we found two gigantic praying mantises, both the brightest of green.  One of the mantises was half brown and the other was all green.  I wrote a little about mantids earlier, but here's some more information about them.

In Tennessee, our most noticeable mantids come in three color variations: green, brown, and green plus brown.  The green ones are European mantids, the brown are Carolina mantids, and the green plus brown are Chinese mantids.  Only the Carolina ones are native, and the other two were introduced to the US to help control garden pests.  These introduced species do not appear to be particularly invasive, though they can reduce numbers of helpful organisms like wolf spiders.  People generally regard them as welcome workers in farms and gardens.   There are several other mantis species that are illegal to import because they pose a threat to native ecosystems.  They can probably reproduce very quickly and overeat beneficial insects.

European mantis, about 6" long.

Female mantises are disconcertingly large this time of year.  They grow big from hunting all season, and their abdomens are filled with eggs.  Now they are laying their egg cases on vegetation.  The egg cases look like brown trilobytes - they are oblong with ridges and about 1-2" long.  They are eggs encased in a foamy mass that hardens after it is laid.  The eggs overwinter to hatch in the spring, releasing hundreds of tiny, springy green mantises into the area.  The tiny, thin mantises need to disperse fast, because their siblings pose a significant predation threat.

Surprises of Fall

Fall came so quickly this year.  Today is the first day of fall, but we have had fall weather for the past several weeks.  Spending entire days every week interacting with the earth and plants has made me notice the season's changes much more acutely this year.  Here are the things I've noticed most as the weather has changed:

• The bees and wasps are already gone.  The flowers are still going strong, but that cloud of buzzing has disappeared.  There are still a few slow bumblebees here and there. 
• The spiders are out in force.  Many blooms have their own resident flower spider, and there are lots of webs strung up between the plants.  We had the biggest garden spider I've ever seen in the hoop house. 
  

  

  Garden Spider Source
  

• It feels strange to eat cherry tomatoes when it's cool and cloudy.  The tomatoes taste the same, it's just not as heavenly to pop them in my mouth when I walk by the tomatoes.  Now I want to nibble the turnip leaves.
• The smell of tomatoes rotting in the field is almost intoxicating.  It's difficult to describe why this is so wonderful, but there's a toasty, dusty, cheesy, roasted tomato smell all around the tomato rows from the unusable tomatoes that makes my head spin.  Rotting squash smell great in the field too.  Don't try this at home - it doesn't work without sunshine and dirt.
• The crops are all different now.  Instead of tomatoes, squash and melons, we have turnips (the best vegetable), chard and beets.  It happened so fast.
• The weeds have slowed down a lot, thank goodness.  Even though I can see the scattered crab grass seeds everywhere, and I know what's ahead for next summer, the pressure's backed off a bit for now.
• It's easy to get a LOT done now that it's not 100 degrees.  In the extreme heat, work slows down due to the body's physiological constraints.  These crisp, cool days mean that I can work fast and easily, and everything feels good.
• I only go fill my water bottle once or twice a day now, instead of four or five times.
• Ironically, the work is starting to taper off even as our capacity to do it increases.  Since fewer crops grow during the winter, a lot of the fields are lying fallow, and we have planted cover crops.  Here is the melon field, all disked in and planted with a mixture of vetch, radish and rye for the winter:

  

  This field is done for the year.
  

• The farm is looking more neat and tidy.  With things growing more slowly, there is time to organize and clean up.  June and July felt like a race to keep up with the creeping jungle of crops and weeds, and now it feels like we are getting ahead.

I only have one or two more days to work on the farm, then I'm moving to the heart of Chicago for a while.  I expect the contrast to be a little jarring.  I'll be reporting on what biological phenomena I observe in the city.  In the mean time, I'm savoring the last few hours of fresh air, big skies and working on the earth here in Middle Tennessee. 

Dangerous Animals Week, Part II

Black Widow Spider (Source)

I bet that image caught your eye!  There is no mistaking a female black widow spider.  When you see one, it is startling.  They are so black and shiny, they stand out against any background.  In my opinion, the extreme blackness of black widows is their most charismatic characteristic - even more so than their red markings.  They are the same black as Wonder Woman's hair.  Their red markings are more variable than you learned in third grade.  Yes, they commonly have a red hourglass under their abdomens, but by the time you notice the red abdomen, you've gotten really close and you've turned over the spider, and it's too late!  Several species of black widow have red splotches on the dorsal side of their abdomens, but the southern black widow has no dorsal splotches.  If you see a jet black shiny and fairly large spider, don't pick it up!

I saw two black widow spiders this week on the farm.  That makes five so far this summer.  I've come to expect them in the drier areas of the farm, like inside the hoop house and the barn.  They also seem more likely to be present on human-made structures, like the irrigation equipment, though this week's spiders were low to the ground on plant stems.  Can you see the black widow in the picture below?

Yes, there is a black widow here.

Here I have zoomed in on the unlucky black widow:

There it is!

When you encounter a black widow, you will notice a rather strange spider web.  Black widows weave chaotic, disorganized and somewhat sparse webs.  Their silk seems to be stronger than other spiders if you happen to put a finger through a web.  The silk has been tested, and it's not stronger, but it is very sticky and somewhat thicker than what other spiders extrude.

For a person who, as a child, thought black widows were always on the hunt for an unsuspecting human to bite, real-life black widows seem shockingly meek.  They cower if their webs are disturbed.  They don't jump or run, but they hold still and hope their warning coloration convinces you to just go away.  The spider above seemed to crouch with it's little legs over its head and quiver when I uncovered it.  I was sorry to kill it, but their bites are so dangerous, we can't tolerate them on the farm.

When you look up black widow spider bites, the medical sites reassure you that 'black widow spider bites are rarely lethal'.  Thanks - that makes me feel a lot better!  Actually, I, personally, am not at great risk, but a bite to a child, elderly person or ill person can be fatal.  Black widows produce a very potent neurotoxin that can spread through the body.  It can produce systemic symptoms like fever, sharp pains, nausea, tremors and worse.  The actual bite location itself will be relatively unimpressive, with a small, red, swollen area.

Most black widow bites are not treated with antivenom (aka antivenin, if you're using the French-derived version of the word).  The antivenom is problematic because it is rarely stocked at hospitals, and it's made from horse serum, which can cause major allergic reactions.  If you are bitten by a black widow, treated with antivenom, then bitten by a rattlesnake, you will be in big trouble.  Rattlesnake antivenom is also made with horse serum, and after your first exposure, your immune system will react much more strongly to the second exposure of horse serum.  Use of antivenom can save the life of an at-risk individual, and it can shorten the flu-like symptoms of a healthy person. 

Black widow spiders get their names from one of the behaviors observed in the female black widows.  Sometimes after mating, female black widow spiders eat the male black widow.  Male black widows generally get the short end of the stick in life.  They are very small, their coloration is drab and they don't have enough venom in their bites to bother anyone.  Their main job in life is to mate and pass on their genes, and after that, they may as well provide a little food to the mother of their children.

Now that the days and nights are getting cooler, I've noticed that the cold-blooded animals on the farm have slowed way down.  The chiggers and ticks seem less intent on making life annoying.  The bees and wasps have mostly disappeared.  The black widows have finished laying eggs and have hopefully lost the strength to push their fangs in through the calloused skin on my hands.

Dangerous Animals Week, Part I

Even farmers go on vacation.  Especially when they get married and go on a honeymoon!  We went to Florida over the weekend, and I took the chance to get to know our gelatinous friends of the sea, the jellyfish and comb jellies!  There are many great mysteries in the ocean, and these critters are some of the least understood - even by Biologists.  I suppose even I have been avoiding them all these years.  I have been so blind.

Jellyfish, corals and sea anemones are all members of Phylum Cnidaria (silent C), which means they are radially symmetrical and have venomous stinging structures.  Comb jellies are members of Phylum Ctenophora (also silent C), which means they are also radially symmetrical but have comb-like cilia and are carnivorous.

I pretty much assumed that everything gelatinous and floaty in the ocean would leave painful welts that would become infected and lead to a costly doctor's appointment.  Wrong!  Many jellyfish have such weak stings that humans can't be punctured.  In fact, the ones I most often see in Florida are mostly harmless to all humans except the most thin-skinned.  The cannonball jellyfish, can apparently cause heart problems if you rub your eyes on its short tentacles, but you can pick it up or brush into it with no problem.  The moon jellyfish, according to the guide to Florida jellyfish that I read while on our honeymoon, do not sting humans.  I did not test this myself, but I did manage to convince my husband to pick one up, and it did not sting him.  Subsequent reading about this species reveals considerable difference of opinion about the the moon jellyfish's ability to sting humans, but the most reliable-sounding Internet sources say it can only mildly sting thin skin.  I chalk the reports of dire consequences up to general fear and misinformation about jellyfish. 

Cannonball Jellyfish

Cannonball Jellyfish

Comb jellies most definitely cannot sting.  Reports are unanimous about this, and I tried it out myself.  Below is a brown comb jelly in the water, and below that are two brown comb jellies in my hand.  Comb jellies are shaped rather like a stocking cap with rows of cilia along the long axis.  Those cilia reflect the sunlight beautifully.  Comb jellies can open and close one end of themselves, depending on whether they are eating something or not.  Since comb jellies are transparent, you can see what they have eaten.  Brown comb jellies eat American comb jellies, which are smaller and colorless.  I watched a brown jelly, which had obviously already eaten once already that day, engulf an American jelly in 5 seconds flat.  Once the prey was inside, the brown jelly sealed itself and probably spent the rest of the day digesting and absorbing its two meals.

A swimming (or is that hunting) brown comb jelly.

A brown comb jelly temporarily collapsed into a pile of goo in my hand.

Brown comb jelly in better light with tree reflection.

Of course, many jellyfish can sting in a major way.  The box jellyfish hurt badly, and some found in Australia are deadly.  The man-of-war can put you in the hospital (incidentally, there is a jellyfish called the by-the-wind jellyfish that looks much like a man-of-war but can't sting people).  There are sea wasps, sea nettles, lion's mane jellyfish and more.  I don't recommend learning which are dangerous by trial-and-error.  Here's a good .pdf guide to Florida jellyfish.

My other major misconception about jellyfish and comb jellies is that they can only stupidly float wherever the current takes them.  Again wrong!  While they are certainly not strong swimmers, jellyfish and comb jellies can move toward and away from things like light, movement, smells and salinity differences.  It's true they don't have brains, but they do have nervous systems to sense the environment and coordinate movements.  Some jellyfish even have fairly complicated camera-type eyes!  Many jellyfish only have to concentrate on staying upright.  Others, like the cannonball jellyfish above, can swim quickly up and down in the water to find food.

Bug Beds

Imagine you are an insect, and the nights are getting colder.  You don't really have a home to go to, but you need a place to snuggle in to survive the cooler nights.  There are a million places you could go.  You could hang under a leaf or sit on a tomato flower, but the real Ritz-Carlton of the insect world is the celosia flower, seen here.

Celosia

Celosias are gigantic, fuzzy, and filled with little crevices to lodge for the night.   There is even breakfast in bed for their guests, because the flowers provide plentiful nectar for bees, wasps and other insects.  I imagine it must be very pleasurable to settle in to these soft, velvety flowers.

Hive-less, or solitary bees will often nestle into or under a flower to get through the night.  If you go into your garden very early in the morning, you will undoubtedly find some sleepy bumble bees or wasps curled up inside your squash flowers or daisies.  If the morning is cool, you can even touch the bees - they will be too cold to panic. 

This week, we had an exceptionally cool day.  It was 95 degrees one day and 60 the next.  The bees and wasps (and the rest of us) were caught off guard, and they didn't leave their flowers for the entire day.  As I harvested celosias, I noticed bumble bees, cicada killer wasps, ichneumon wasps and many other wasps and bees sitting inactive amongst the celosia blooms.  I could get as close to them as I wished without disturbing them.  Unfortunately it was also raining, so I didn't get pictures.  You'll have to make do with this picture of a cart loaded with gorgeous celosias that I harvested. 

Cart of celosias

I C4...there I am!

Sorry for the bad pun!

It's the hottest and sunniest time of the year.  That means the C4 plants are about to lap the C3 plants in the race on the farm.  C4 plants are ones that have evolved an extra step to their photosynthesis process that makes them more efficient than other plants, especially during the heat of summer.  Most plants are C3 plants, but crabgrass, sugar cane, corn, sorghum and many other plants are C4 plants.  C4 plants comprise only about 3% of flowering plants, but they do 25% of the photosynthesis that occurs on land*.  Unfortunately, the only C4 plants on the farm are weeds, and the worst of the worst is crabgrass!!!!!

My nemesis.  Notice the star shape of the first few crabgrass stems.

Now brace yourself.  We're going to have to wade into some technicalities of photosynthesis.  Trust me...it's way cool, as the young kids say.  It is imperative that you understand the tricks that C4 plants can do, because if you ever have to spend an entire day weeding crabgrass, you'll want something to think about.

First though, C3.  Think back to 9th grade.  Remember photosynthesis?  It's that thing that plants do to make their food.  The idea is that plants capture the energy that the sun is giving off, and then they use that energy to knit carbons, hydrogens and oxygens together to make sugar.  As we all know, sugar is a basic food.  In plants, it stores the sun's energy in chemical form until the plant needs it.  Sugar is also the basic molecular building block for a lot of the structural molecules plants use to build themselves.  In fact, all the food on our entire planet originated from photosynthesis (even meat because cows get their energy from grass).  Also, all the oxygen in the air on Earth was made as a byproduct of photosynthesis.  So it's kind of important.

Now to the name C3.  The C refers to carbon, which is the most important atom involved in photosynthesis.  Plants collect carbons form the air in the form of carbon dioxide, which they use to make sugar.  The 3 refers to the size of the molecule that the plant uses to 'trap' the carbon dioxide.  In C3 plants, when a carbon dioxide molecule (which has one carbon atom) is caught by the plant, it joins with the plant's carbons to make a three-carbon molecule (called 3-phosphoglyceric acid, or PGA).  Eventually, when a plant has collected six carbon dioxide molecules, it has enough carbons to make one sugar molecule.  In a single teaspoon of plant sugar, there are approximately 1.7 x 10^22 molecules of sugar, so plants do a LOT of photosynthesis.

But, you can't understand the C4s' advantage until you understand the last piece of this photosynthesis puzzle: RUBISCO.  I'm not just typing in all caps because I'm excited about RUBISCO; it's also an acronym.  RUBISCO stands for ribulose 1,5 bisphosphate carboxylase oxygenase, which is a handy phrase to work into almost any conversation.  RUBISCO is the molecular machine, or enzyme, that allows the plant to 'grab' CO2 out of the air and bond it to make the three carbon molecule.  The carboxylase part of the name refers to its ability to bond carbon.  Unfortunately for plants, RUBISCO can also bond oxygen (that's the oxygenase part of its name).  It's unusual for enzymes to be able to bond two different substrates - usually they have one job only.  For RUBISCO, it's a problem to be able to bond two things, because every time the RUBISCO bonds to oxygen instead of carbon dioxide, it costs the plant energy instead of gaining energy like photosynthesis is supposed to do.  In the summer, when plants are photosynthesizing fastest (and producing oxygen, remember), there is even more oxygen around the plant.  So plants are not able to photosynthesize to their full potential because their RUBISCO is wasting more time with oxygen.  Scientists think the RUBISCO problem exists because RUBISCO evolved in plants' ancestors before there was any oxygen in the air to worry about.

It all used to look like the right side before I pulled out the crabgrass.

C4 plants have evolved more recently, and they have solved the RUBISCO paradox.  As you can see in the pictures above and below, the C4 crabgrass is kicking the butts of the C3 beets growing in identical conditions. 

Unweeded beets on the left, free beets on the right.

 Crabgrass, like all other C4 plants, bonds carbon dioxide to make a....drum roll please.....FOUR carbon molecule!!!  Crabgrass has a stand-in molecule that doesn't use RUBISCO to trap carbon dioxide from the air.  This C4 molecule exists near the surfaces of the plants that are exposed to air, where carbon dioxide (and oxygen) is.  It can ONLY trap carbon dioxide and not oxygen.  Once it traps a carbon dioxide, the four-carbon molecule, called oxaloacetic acid, travels deep into the plant away from air.  All the plant's RUBISCO is stored near the center of the plant's leaves and stems, and the oxaloacetic acid drops off the trapped carbon to RUBISCO, where it goes through the rest of photosynthesis like normal.  So you have all of the photosynthesis with none of the waste from exposure to oxygen.  And thus the crabgrass flourishes in the middle of summer when photosynthesis is happening at its fastest.

* Most of the photosynthesis that occurs on earth is done by algae in the ocean.

Zombie Worms From Planet Sphinx

This time of year, when you're harvesting tomatoes, you often notice part of the plant where the leaves seem to be missing and all that's left are stubby stems.  This is not a deformed tomato plant.  Look closely and you will see a stem that seems to be especially thick and stubby like so: 

Tobacco Horn Worm (Source)

The gigantic worm above is a tobacco horn worm.  It is a positively ravenous caterpillar that literally stuffs itself with tomato or tobacco leaves.  If you touch one, it seems to be so full that its skin feels like a grape leaf around a dolma.  It eats so much of the tomato plant that it can reduce tomato productivity dramatically.  Farmers dislike these caterpillars, but I bet most of them also admire the strangeness of these creatures. 

Tobacco horn worms grow from tiny eggs deposited on tomato plants by the Carolina sphinx moth, a gorgeous night creature that moves and hovers like a hummingbird.  It has a coiled proboscis that it uses to probe nectar from night-blooming flowers trumpet-shaped flowers.  Here is a sphinx moth feeding on an azalea:

Sphinx moth feeding.  (Source)

 Sometimes when you see a tobacco horn worm, it will appear to be covered with dozens of white, ovoid bead-like objects.  When you see this, you know the horn worm is one of the walking dead.  The white things are the pupal cases of a type of braconid wasp, which lays its eggs under the skin of the horn worm.  The eggs hatch inside the horn worm and eat the worm from the inside out.  The larvae begin to burst out of their horn worm and weave little white cases with lids around themselves.  In a few days, they will emerge as adult wasps, and the horn worm will expire as a shrunken husk of itself.  The adult wasps will go on to infect and kill other horn worms.  Braconid wasps are friends of the farmer because they help do the work of dispensing with horn worms.  Anytime a farmer sees an infected horn worm, she lets it be so that more wasps will hatch.  Farmers can even order braconid wasps in the mail to release on their farms.  Here is an infected horn worm:

I know it's hard to see, but there is a parasitised tobacco horn worm in the middle of the picture.  I'll bring a better camera to work tomorrow.

 Here are some better pictures I didn't take from this website:

A good picture of an infected hornworm.

An adult braconid wasp spreading its wings for the first time.