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Assignment for The Forest Unseen: “February” Due Monday, 20 September 2021 by the start of class For the February chapters (pp

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Assignment for The Forest Unseen: “February” Due Monday, 20 September 2021 by the start of class For the February chapters (pp. 25-45), choose two of your favorite examples from those readings that describe two different evolutionary concepts. For each example, identify the evolutionary concept and then briefly explain the general concept, defining terms and “teaching” the concept to the reader. Next, clearly illustrate how the case you chose is a good example of that evolutionary concept – link the example (specific case) to the concept. Each set of concept/example should produce a maximum of 1 page of text. Finally, at the end of the essay, discuss connections between the author’s observations in the February chapters and your own personal experiences. For example, in the chapter, “January 30th – Winter Plants”, Haskell discussed how plants modify their cells in several ways as winter approaches (that’s the example). The relevant concept is adaptation, specifically physiological adaptation in this case. Thus, you would explain the concept of adaptation, and you would describe how plant cells illustrate that concept. Use concepts that we have discussed in class or from the reading assignments. You can go all the way back to the first day of class. The assignment should be word processed and double spaced, with page numbers included. The entire assignment should be free of spelling, punctuation, and grammatical errors, so please proofread carefully. Assignment for The Forest Unseen: “February” Due Monday, 20 September 2021 by the start of class For the February chapters (pp. 25-45), choose two of your favorite examples from those readings that describe two different evolutionary concepts. For each example, identify the evolutionary concept and then briefly explain the general concept, defining terms and “teaching” the concept to the reader. Next, clearly illustrate how the case you chose is a good example of that evolutionary concept – link the example (specific case) to the concept. Each set of concept/example should produce a maximum of 1 page of text. Finally, at the end of the essay, discuss connections between the author’s observations in the February chapters and your own personal experiences. For example, in the chapter, “January 30th – Winter Plants”, Haskell discussed how plants modify their cells in several ways as winter approaches (that’s the example). The relevant concept is adaptation, specifically physiological adaptation in this case. Thus, you would explain the concept of adaptation, and you would describe how plant cells illustrate that concept. Use concepts that we have discussed in class or from the reading assignments. You can go all the way back to the first day of class. The assignment should be word processed and double spaced, with page numbers included. The entire assignment should be free of spelling, punctuation, and grammatical errors, so please proofread carefully. February 2nd-Footprints and chew woody material, but they cannot digest cellulose, the molecule that constitutes most plant matter. Microbes, tiny sin- gle-celled organisms such as bacteria and protists, are physically puny but chemically powerful. Cellulose does not give them pause. Thus is born a gang of thieves: animals that walk around and grind up plants, paired with microbes that digest pulverized cellulose. Several groups of animals have independently devel- oped this plan. Termites work with protists in their gut; rabbits and their kin harbor microbes in a large chamber at the end of their gut; the hoatzin, an improbable leaf-eating bird from South America, has a fermentation sac in its neck; ruminants, includ- ing deer, have a huge bag of helpers in a special stomach, the The tips of a maple-leaf viburnum have been chiseled off , rumen. Microbial partnerships allow large animals to use the vast stores of energy locked up in plant tissues. Those animals, including humans, that have not entered into a deal with microbes are limited to eating soft fruits, a few easily digestible seeds, and the milk and flesh of our more versatile animal cousins. leaving beveled stubs along the shrub's branches. The ani- mal that clipped these tender shoots has left three footprints in the mandala, aligned east to west. Two almond-shaped impres- sions make up each footprint, sunk two inches into the leaf lit- ter. This is the signature of a cloven hoof, the seal of the artiodactyl clan. Like nearly every terrestrial community the world over, the mandala has been browsed by a cleft-hoofed mammal, in this case a white-tailed deer. The deer that passed through the mandala last night was care- ful in its choice of browse. The viburnum shrub had stored food in branch tips, readying itself for spring. These young tips were not yet toughened and woody. The shrub's tender growth has now been robbed, digested, and reinvested in deer muscle or, if the nibbler was a doe, in the body of a fawn in her womb. The deer had help. Freeing the food locked inside the tough cells of twigs and leaves requires a partnership between the very large and the very small. Big multicellular animals can nip off The saplings in the mandala were pinched between the deer's lower teeth and the tough pad on its upper jaw that takes the place of upper front teeth. The woody morsels were sent to the back teeth to be ground up, then swallowed. When these pieces hit the rumen they entered another ecosystem, a huge churning vat of microbes. The rumen is a sac that branches off the rest of the deer's gut. All food, except the mother's milk, is sent to the rumen before it can move into the rest of the stomach, then on to the intestines. The rumen is surrounded by muscles that churn the contents. Flaps of skin inside the rumen act like baf- fles in a washing machine, flipping the food over as it moves. Most microbes in the rumen cannot live in the presence of oxygen. They are descendants of ancient creatures that evolved in a very different atmosphere. Only when photosynthesis was invented, about two and a half billion years ago, did oxygen become part of earth's air and, because oxygen is a dangerous, reactive chemical, this poisoning of the planet wiped out many creatures and forced others into hiding. These oxygen-haters live to this day in lake bottoms, in swamps, and deep in the soil, eking out an existence in oxygen-free environments. Other crea- tures adapted to the new pollutant and, using an elegant side- stepping maneuver, turned the toxic oxygen to their advantage. Thus was born respiration using oxygen, an energy-liberating biochemical trick that we have inherited. Our lives therefore depend on an ancient form of pollution. The evolution of animal guts gave the oxygen-hating refugees a potential new place in which to hide. Not only are guts rela- tively free of oxygen, they also have every microbe's dream: a continual supply of minced food. But there was a problem. Ani- mal stomachs are generally full of acidic digestive juices designed to tear apart living tissue. This prevented most animals from harboring plant-digesting microbes. However, the rumi- nants changed their stomachs, mastering the hotelier's art, and they have been rewarded by a four-star rating of evolutionary success. The centerpiece of this hospitality is the position and friendliness of the rumen, which comes before the rest of the gut and is kept neutral, neither acid nor alkaline. Microbes thrive in this churning spa. The animal's saliva is alkaline, so the acidic products of digestion are neutralized. Any incoming oxygen is soaked up by a small team of bacterial chambermaids. The rumen functions so well that scientists equipped with the most sophisticated test tubes and vats have not been able to replicate, let alone beat, the growth rate or digestive prowess of the rumen's microbes. The rumen's performance is due to the exquisite biological complexity that thrives in its pampered chambers. A million million individual bacteria of at least two hundred species swim through every milliliter of rumen fluid. Some of these microbes have been described; others await description or discovery. Many of the microbes are found only in rumens, presumably having diverged from their free-living ancestors during the fifty-five million years that have passed since the rumen's origin. Within the rumen, the bacterial proletariat is preyed upon by a bevy of protists, all of which are single-celled but hundreds or thousands of times bigger than the bacteria. Fungi parasitize these protists, infecting then bursting the fat cells. Other fungi float free in the rumen fluid or colonize scraps of plant material. The diversity of life in the rumen makes possible the complete digestion of the plant remains. No single species can fully digest a plant cell. Each species takes a small part of the overall process, chopping up its favorite molecules, harvesting the energy it needs to grow, and then sending back its wastes to the rumen fluid. These wastes become another creature's food, building a cascading web of disassembly. Bacteria destroy most of the cellulose, aided by some fungi. Protists have a special fondness for starch grains, perhaps regarding them as potatoes to accompany their meal of bacterial sausages. Nutrients is the Page 47 Page 48 9 pages left in this chapter rumen are passed up a miniature food web, then released back into the rumen’s fluid, mimicking the nutrient cycles of larger ecosystems. The deer's belly contains a mandala of its own, an intricate dance of lives, sustained by hungry lips and teeth. Young ruminants must build their rumen community from scratch, a process that takes several weeks. During this time, they nibble their mother, the soil, and the vegetation, gathering and swallowing the microbes that will become their helpers. The rumen's ecosystem is a self-sacrificing mandala, embody- ing endless change. Microbes are carried out of the rumen along with digested plant cells. They travel to the second part of the deer's stomach and are swamped with acid and digestive juices. For these microbes, the gut's hospitality has ended. The innkeeper kills and digests them, pocketing their proteins and vitamins along with the liquefied plant remains. The rumen retains plant solids and the microbes that cling to them, ensuring both the complete digestion of the plant and the continuity of the rumen’s microbial community. The deer has- tens the breakdown of these solids by bringing them back into its mouth, chewing the cud, then swallowing the pulverized remains. This rumination allows the deer to "wolf” down its food, literally on the hoof, then chew it in a safe hiding place, away from real wolves. As the seasons change, the deer's browsing moves from one part of the plant to another. The woody food of winter will change to springtime greenery, then autumn acorns. The rumen adapts to these changes through the gradual waxing and waning of the members of its community. Bacteria suited to digestion of soft leaves increase through the spring, then taper away in win- ter. No top-down control by the deer is needed to direct this change; competition among the rumen inhabitants automatically matches the rumen's digestive capabilities to the food available. But sudden changes in diet can disrupt this elegant molding of the rumen community to its environment. If a deer is fed corn or leafy greens in the middle of winter, its rumen will be knocked off balance, acidity will rise uncontrollably, and gases will bloat the rumen. Indigestion of this kind can be lethal. Young rumi- nants face a similar digestive problem when they suckle their mother's teats. Milk would ferment and create gas in the rumen, especially in immature animals whose rumens have yet to be fully colonized by microbes. The sucking reflex therefore triggers the opening of a bypass that sends milk past the rumen, into the next part of the stomach. Nature seldom throws rapid dietary change at ruminants, but when humans feed domesticated cows, goats, or sheep, they must address the rumen's needs. These needs do not necessarily conform to the desires of human commodity markets, so the rumen's balance is the bane of industrial agriculture. When cows are taken from pasture and suddenly confined to feedlots to be fattened on corn, they must be medicated to pacify the rumen community. Only by stamping down the microbial helpers can we try to impose our will on the cow's flesh. Fifty-five million years of rumen design versus fifty years of industrial agriculture: we face questionable odds. The deer's effects in the mandala were subtle. At first glance, shrubs and saplings appear unmolested. Only close observation reveals the missing tips of branches and the short, ampu Page 49 Page 50 7 pages left in this chapter stubs of side shoots. About half the dozen shrub stems in the mandala have been trimmed, but none of them have been cut back to stumps. I infer that deer and their microbial companions are frequent visitors to the mandala, but the deer are not starv- ing. They can afford to nibble the succulent ends of twigs, leav- ing the woody stems behind. This choosiness is becoming a threatened luxury among white-tailed deer in the eastern forests. Across much of the deer's range plant defenses are deployed in vain: deer populations have expanded rapidly, and the teeth and rumens of these growing hordes have sterilized the forest of saplings, shrubs, and wildflowers. Many ecologists claim that the recent growth of the deer pop- ulation is a continentwide catastrophe. Equivalent, perhaps, to throwing corn into a winter rumen; the community is thrown into an unnatural disequilibrium. The case against the deer seems unassailable. Deer numbers are growing. Plant popula- tions are in decline. Shrub-nesting birds cannot find nest sites. Tick-borne diseases lurk on suburban lawns. We have eliminated predators, first Native Americans, then wolves, then modern hunters, whose numbers dwindle each year. Our fields and towns have cut the forest into ribbons and rags, creating the edge habitat in which deer love to feed. We have carefully nur- tured deer populations with game-protection laws that time the hunting season to have the smallest possible effect on the deer population. Surely the forest's viability is endangered? Perhaps, but a longer view adds some mists of uncertainty to this black-and-white portrait of the role of deer in the eastern forests. Our cultural and scientific memories of what a "normal" forest should look like arose at a peculiar moment in history, a moment when deer, for the first time in millennia, had been extirpated from the forest. Large-scale commercial hunting in the late nineteenth century edged the deer population toward extinction. Deer were eliminated from most of Tennessee, including from this mandala. No deer visited the mandala between 1900 and the 1950s. Then, releases of deer transplanted from elsewhere, combined with elimination of bobcats and feral dogs, gradually pushed the population of deer upward until the 1980s, when deer were once again abundant. A similar pattern was replicated across the eastern forest. This history distorts our scientific understanding of the forest. Most of the scientific studies of eastern North American forest ecology in the twentieth century were conducted in an abnor- mally unbrowsed forest. This is especially true of the older stud- ies that we use as a benchmark to measure ecological change. The benchmark is misleading: at no other time in the history of these forests have ruminants and other large herbivores been absent. Our memory, therefore, recalls an abnormal forest, limp- ing along without its large herbivores. Disquieting possibilities grow out of this history. Wildflowers and shrub-nesting warblers may be experiencing the end of an unusual era of ease. “Overbrowsing” by deer may be returning the forest to its more usual sparse, open condition. The surviv- ing diaries and letters of early European settlers lend some sup- port to these ideas. Thomas Harriot wrote from Virginia in 1580 that “of... deare, in some places there are great store”; Thomas Ashe reports in 1682 that “there is such infinite herds, that the whole country seems but one continued park"; Baron de La Han- Page 51 Page 52 5 pages left in this chapter February 2nd-Footprints and chew woody material, but they cannot digest cellulose, the molecule that constitutes most plant matter. Microbes, tiny sin- gle-celled organisms such as bacteria and protists, are physically puny but chemically powerful. Cellulose does not give them pause. Thus is born a gang of thieves: animals that walk around and grind up plants, paired with microbes that digest pulverized cellulose. Several groups of animals have independently devel- oped this plan. Termites work with protists in their gut; rabbits and their kin harbor microbes in a large chamber at the end of their gut; the hoatzin, an improbable leaf-eating bird from South America, has a fermentation sac in its neck; ruminants, includ- ing deer, have a huge bag of helpers in a special stomach, the The tips of a maple-leaf viburnum have been chiseled off , rumen. Microbial partnerships allow large animals to use the vast stores of energy locked up in plant tissues. Those animals, including humans, that have not entered into a deal with microbes are limited to eating soft fruits, a few easily digestible seeds, and the milk and flesh of our more versatile animal cousins. leaving beveled stubs along the shrub's branches. The ani- mal that clipped these tender shoots has left three footprints in the mandala, aligned east to west. Two almond-shaped impres- sions make up each footprint, sunk two inches into the leaf lit- ter. This is the signature of a cloven hoof, the seal of the artiodactyl clan. Like nearly every terrestrial community the world over, the mandala has been browsed by a cleft-hoofed mammal, in this case a white-tailed deer. The deer that passed through the mandala last night was care- ful in its choice of browse. The viburnum shrub had stored food in branch tips, readying itself for spring. These young tips were not yet toughened and woody. The shrub's tender growth has now been robbed, digested, and reinvested in deer muscle or, if the nibbler was a doe, in the body of a fawn in her womb. The deer had help. Freeing the food locked inside the tough cells of twigs and leaves requires a partnership between the very large and the very small. Big multicellular animals can nip off The saplings in the mandala were pinched between the deer's lower teeth and the tough pad on its upper jaw that takes the place of upper front teeth. The woody morsels were sent to the back teeth to be ground up, then swallowed. When these pieces hit the rumen they entered another ecosystem, a huge churning vat of microbes. The rumen is a sac that branches off the rest of the deer's gut. All food, except the mother's milk, is sent to the rumen before it can move into the rest of the stomach, then on to the intestines. The rumen is surrounded by muscles that churn the contents. Flaps of skin inside the rumen act like baf- fles in a washing machine, flipping the food over as it moves. Most microbes in the rumen cannot live in the presence of oxygen. They are descendants of ancient creatures that evolved in a very different atmosphere. Only when photosynthesis was invented, about two and a half billion years ago, did oxygen become part of earth's air and, because oxygen is a dangerous, reactive chemical, this poisoning of the planet wiped out many creatures and forced others into hiding. These oxygen-haters live to this day in lake bottoms, in swamps, and deep in the soil, eking out an existence in oxygen-free environments. Other crea- tures adapted to the new pollutant and, using an elegant side- stepping maneuver, turned the toxic oxygen to their advantag...