In this class, we examine questions such as the following:
Why am I here? What is the purpose of my life?
Why are some genes dominant while others are recessive?
Why do most, but not all, species reproduce by sexual reproduction?
Why did sexual reproduction evolve and how is it maintained in face of the huge cost of passing on the genes of another individual rather than just one's own?
Why are sex ratios often near 50:50?
Why do females and males often differ in size and strength?
Why do females have longer life expectancies than males?
Why do female humans undergo menopause, but males do not?
Why are some species promiscuous, others monogamous, and still others polygamous?
Why are we jealous of our mates when they flirt with others of our own sex?
How do parasites, including sexually-transmitted diseases, evolve?
How do parasites influence the behavior of their hosts?
Why are some individuals, such as bees and wasps, so willing to give up their own lives in defense of others?
Why are some species rare, but others abundant?
Why are some species specialized and others generalized?
Why are some species much more fecund than others?
Why do many species of birds migrate in the autumn?
Why do we become senile as we grow old? Must we die?
In this course, you will learn to think in terms of natural selection, and you will be given the tools to understand why any biological phenomenon has evolved.
Most people consider the study of biology, particularly ecology, to be a luxury that they can do without. They are wrong. Even medical schools no longer require that premedical students major in biology. Basic biology is hardly a luxury, but rather an absolute for all living creatures. Other life forms are not irrelevant to our own existence. We rely on other organisms for food, medicine, shelter, and clothing. An understanding of basic parasitology is needed to control epidemics in human populations. Similarly, knowledge of basic principles of community organization and ecosystem function are essential for wise exploitation of both natural and agricultural ecological systems.
What good are lizards? Indeed, what good are you?
With human populations burgeoning and pressures on space and other limited resources intensifying, we need all the biological knowledge that we can possibly get. Ecological understanding is particularly vital.
There is a great urgency to basic ecological research simply because the worldwide press of humanity is rapidly driving other species extinct and destroying the very systems that ecologists seek to understand. No natural community remains pristine. Unfortunately, many will disappear without even being adequately described, let alone remotely understood. As existing species go extinct and even entire ecosystems disappear, we lose forever the very opportunity to study them. Knowledge of their evolutionary history and adaptations vanishes with them: we are thus losing access to biological information itself. Indeed, "destroying species is like tearing pages out of an unread book, written in a language humans hardly know how to read" (Rolston, 1985). Just as ecologists are finally beginning to learn to read this "unread" and rapidly disappearing book of life, they are encountering governmental and public hostility and having a difficult time attracting support. This is simply pitiful. And time is quickly running out.
Pristine natural ecological systems hold precious information about community organization that we cannot afford to lose. We must preserve them and study them. Beyond such human-oriented arguments, other species have a right to exist, too, as proven products of natural selection that have adapted to natural environments over millennia.
This course emphasizes basic ecological principles, many of which have obvious and important applications. For example, optimal yield to maximize sustained harvests have long been goals in wildlife management and fisheries biology. An emerging discipline of conservation biology seeks to conserve natural habitats and maintain biotic diversity. Biodiversity constitutes a valuable resource worthy of preservation for many different reasons. Genetic strains of plants with natural resistance to pests are valuable because their genes can be exploited to confer resistance on future crop plants.
Approximately one drug in four originated in a rainforest: these include analgesics, diuretics, laxatives, tranquilizers, contraceptive pills and cough drops. Antibiotics were first discovered in fungi, but have now also been found in many species of plants as well. Secondary chemicals of plants have proven to be a vast reservoir for useful pharmacutical products. Clinically proven drugs derived from higher plants include: morphine, codeine, atropine, quinine, digitalis, and many many others. Recently, it was discovered that bark of Pacific yew trees contains taxol, which has proven to be an effective agent in the treatment of certain ovarian cancers. To date, scientists have examined only about one percent of existing plant species for useful pharmacuticals.
Powerful pharmacological agents have recently discovered in the venom of one of only two venomous lizards, the Gila monster. Complex mixtures of over a dozen small peptides, neurotransmitters, proteins, and other molecules, have powerful effects on mammalian physiology. Natural selection has invented molecular analogs that mimic important mammalian hormones such as the neurotransmitter serotonin, secretin, and a variety of peptides and proteins. One lowers blood pressure, another regulates insulin release, while still another attacks certain cancers. Yet another, a peptide called gilatide, improves memory in rats and is a candidate for development of a drug to treat Alzheimer's disease. Such molecules could prove to be useful drugs to control hypertension, diabetes, and cancer. One such drug. Exendin-4, derived from Gila monster venom is currently being evaluated for treatment of type II diabetes. Some, but not all, of these molecules are also found in snake venoms, which tend to be much more toxic.
Modern molecular biotechnological tools, such as restriction enzymes and gene splicing, now enable geneticists to transfer particular genes from one organism to another. Other techniques, such as polymerase chain reaction (PCR) amplification of DNA seqments, DNA sequencing and fingerprinting hold great promise as tools that will allow informative evolutionary studies. For example, the firefly gene for luciferase has been successfully transfered to tobacco, resulting in transgenic bioluminescent plants. Human insulin and growth hormone are now routinely produced in chemostats of the human gut bacterium Escherichia coli that have had human genes spliced into their genomes. Transgenic cows produce milk containing medically useful proteins such as human blood clotting factors (useful for hemophiliacs!) Genetically altered transgenic bacteria have been used as living vaccines that confer resistance to particular diseases such as typhoid. Pest resistance and nitrogen-fixing genes are being spliced into crop plants with the hope of vastly increasing yields. Any day now, some enterprising genetic engineer will transplant elephant growth genes into cattle to make bigger and better cows! You want a bigger chicken?: I'll transplant some ostrich genes into chickens! We are audaciously bypassing natural selection and creating whatever phenotypes we think best.
Such recombinant DNA technology has also enabled us to produce useful new life forms such as pollutant-eating bacteria that can help us to clean up what's left of our environment. There are legitimate concerns, however, about the safety of research on such man-made transgenic organisms, particularly the possibility of accidental release of virulent strains that might attack humans. Such concerns have been addressed by implementation of strict containment procedures for recombinant DNA products, as well as by selecting and creating host organisms for foreign DNA that are incapable of surviving outside the laboratory. However, the genie has already gotten out of the bottle.
A large percentage of US crops (corn, soybeans, cotton, tomatoes, etc) are genetically engineered and are now being grown commercially. A bacterial gene (Bt) that produces an insecticide was spliced into the genome of corn to confer protection against corn borers. Corn is wind pollinated, and genetically engineered Bt pollen has now polluted the gene pool of corn crops in Mexico. More transgenic organisms will eventually be released into nature, and the process may be irreversible. Genetically-engineered organisms could have adverse effects on other species in natural ecosystems. We already have enough natural pests and certainly don't want man-made ones! Unfortunately, we still know far too little to engineer ecological systems intelligently (obviously genetic engineers should work hand in hand with ecological engineers). Still another problem is the human tendency to allow short-term financial returns to override long-term prospects.
Conflict Between Human Activities and Preservation of Wilderness
Most people hold the opinion that Earth exists primarily, or even solely for human exploitation. Genesis prescribes: "Be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth" (my italics). We have certainly lived up to everything except "replenish the earth."
The human population explosion has been fueled by habitat destruction -- we are usurping resources once exploited by other species. Massive consumption of fossil fuels for argriculture has also contributed greatly to overpopulation.
Tall grass prairies of North America have been replaced with fields of corn and wheat, native American bison have given way to cattle, etc. Humans now consume (primarily via fisheries, agriculture, pastoral activities, and forestry) HALF of the planet's total production. Today we consume more than half of available freshwater as well as over half of the solar energy trapped by plants. Many species have gone extinct due to human pressures over the past century and many more are threatened and endangered. Once we were surrounded by wilderness and wild animals, but now we surround them.
During the past quarter of a century, world population has increased from about 3.4 billion people to over 6.4 billion, an increase of over 85%. In some parts of the world, human populations are growing even faster.
If humans do not control their own population (and we seem unwilling and unable to do so), then other forces will certainly act to control our population. The four horseman of the apocalypse (conquest, war, famine, and death) are all candidates. Most likely, lethal virulent microbes like HIV and Ebola zaire will set limits on the growth of human populations. HIV, by allowing infected hosts to survive years while they spread the virus and infect new hosts, has already become a pandemic, but it will be years before it decimates the human population. Although Ebola kills 9 out of 10 people, outbreaks have so far been unable to become epidemics because they are currently spread only by direct physical contact with infected blood. However, a closely related virus that kills monkeys, Ebola reston, is airborne, and it is only a matter of time until Ebola zaire evolves the capacity to be airborne.
People everywhere today stand ready to rape and pillage their wildernesses ("wastelands") for whatever they can be forced to yield. Raw materials, such as ore, lumber, and even sand (used to make glass), are harvested in vast quantities. Big companies enjoy privileged status, excluding the public from extensive areas, producing great ugly clear cuts, vast deep open pit mines, instant but permanent, man-made mountains, eyesores paying testimony to the avaricious pursuit of timber, precious metals and minerals. Deforestation is nearly complete in many parts of the world. Overgrazing is rampant. Grasses and the shrub understory have been virtually eliminated over extensive areas. It is quite instructive to come upon a fenced graveyard, and to see a small patch of country as it must have been before the land rape by the pastoral industry. Native hardwoods are wasted to make charcoal and burned for firewood. Lumberjacks will soon be out of work whether or not the remaining timber is cut. Should forest habitats be saved? Is there enough left to save? This sort of pillage continues. Virtually everywhere, often with governmental subsidies and incentives, forests, deserts, and scrublands are being levelled and turned into fields for crops. Many of these fields are marginal and will soon have to be abandoned, transformed into great man-made vegetationless deserts. More dust bowls are in the making.
In some regions, such as Australia, replacement of the drought-adapted deep rooted native vegetation with shallow rooted crop plants has reduced evapotranspiration, thus allowing the water table to rise, bringing deep saline waters to the surface. Such salinization reduces productivity and seems to be irreversible. Some deserts have so far been able to resist the tidal wave of advancing human exploiters, but there are people who dream of the day that technological "advances," such as water plans to move "excess" water or the distillation of sea water, will make it possible to develop desert regions (i.e., to replace them with vast agricultural fields, or even cities). Antonyms, such as "sustainable development," are strung together by politicians and developers to make oxymorons in an attempt to make all this destruction and homogenization seem less offensive.
Only during the last few generations have biologists been fortunate enough to be able to travel with ease to remote wilderness areas. Panglobal comparisons have broadened our horizons immensely. This is a fleeting and unique opportunity in the history of humanity, for never before could scientists get virtually anywhere. However, all too soon, there won't be any pristine natural habitats left to study.
The Tragedy of the Commons
Nearly twenty years ago, in a setpiece of rational thought that deserves much more attention than it has so far received, Garrett Hardin [Science 162: 1244 (1968)] perceived a fly in the ointment of freedom, which he explained as follows:
"The tragedy of the commons develops in this way. Picture a pasture open to all. It is to be expected that each herdsman will try to keep as many cattle as possible on the commons. Such an arrangement may work reasonably satisfactorily for centuries because tribal wars, poaching, and disease keep the numbers of both man and beast well below the carrying capacity of the land. Finally, however, comes the day of reckoning, that is, the day when the long-desired goal of social stability becomes a reality. At this point, the inherent logic of the commons remorselessly generates tragedy.
As a rational being, each herdsman seeks to maximize his gain. Explicitly or implicitly, more or less consciously, he asks, "What is the utility to me of adding one more animal to my herd?" This utility has one negative and one positive component.
1) The positive component is a function of the increment of one animal. Since the herdsman receives all the proceeds from the sale of the additional animal, the positive utility is nearly +1.
2) The negative component is a function of the additional overgrazing created by one more animal. Since, however, the effects of overgrazing are shared by all the herdsman, the negative utility for any particular decision-making herdsman is only a fraction of -1.
Adding together the component partial utilities, the rational herdsman concludes that the only sensible course for him to pursue is to add another animal to his herd. And another; and another . . . But this is the conclusion reached by each and every rational herdsman sharing a commons. Therein is the tragedy. Each man is locked into a system that compels him to increase his herd without limit in a world that is limited. Ruin is the destination toward which all men rush, each pursuing his own interest in a society that believes in the freedom of the commons. Freedom of the commons brings ruin to all."
Hardin's logic is compelling: overgrazing of public lands and overfishing of the oceans serve as ample testimony to its accuracy. He extends his argument to pollution and unlimited reproduction, noting that the "tragedy of the commons" theme recurs and underlies these and other serious human problems. Hardin suggests that a commons is acceptable only at low population densities and that we can no longer afford to have commons. But it is not so easy to escape from this trap: the Earth and its atmosphere themselves constitute commons that all humans must share whether we like it or not.
Examples include the rush to catch the last of the great whales and the ongoing destruction of earth's atmosphere (ozone depletion, acid rain, carbon dioxide enhanced greenhouse effect, etc.). Global weather modification is a very real and an exceedingly serious threat to all of us, as well as to all other species of plants and animals struggling to continue their existence on this planet.
Earth's atmosphere is unusual in that it has a relatively high oxygen content (about 21 per cent). Most other planets have a reducing atmosphere. The free oxygen in today's atmosphere was probably produced largely by the activities of primary producers. The most plausible hypothesis to explain our planet's rather unusual atmosphere is that activities of living organisms, particularly green plants and certain bacteria, play vital roles in the building and maintenance of air. Photosynthetic activities of plants utilize carbon dioxide and water to produce oxygen as a by-product, along with energy-rich reduced carbon compounds, such as glucose. Free oxygen is released into the atmosphere by an inanimate process, too. High in the atmosphere above the ozone shield, ionizing solar radiation dissociates water vapor into molecular hydrogen and oxygen. Free oxygen is left behind as the light hydrogen atoms escape into outer space. In a reduced atmosphere, oxidation quickly uses up such free oxygen. Both of these oxygen-generating mechanisms have been important; dissociation was probably much more significant billions of years ago before the ozone layer was formed than it is at present (it will become more important as the ozone layer is further thinned by the release of chloroflourocarbon gases). Ozone depletion has also increased ultraviolet radiation at the surface, which has almost certainly increased the frequency of skin cancers (though these may not be detectable for another decade).
Our atmosphere is in a complex quasi-equilibrium, although the concentration of carbon dioxide has risen steadily for the last quarter of a century and continues to rise due to deforestation and the burning of fossil fuels. Over the past 30 years, consumption of fossil fuels (measured in millions of tons of carbon emissions), increased from 2547 per year to 5600 worldwide (a 120% increase). [To generate this amount of carbon dioxide metabolically, every man, woman and child on the planet would have to eat approximately 50 kg (about 110 pounds) of potatoes each and every day of his/her life!] Carbon emission increased by 55% in the US and by a whopping 170% in Australia. Per capita consumption of fossil fuel in both the US and Australia is 4 to 5 times above the world average.
This increase in atmospheric carbon dioxide has enhanced atmospheric heat retention and would have produced global warming sooner except for dumb luck -- a fortuitous spin-off of atmospheric pollution is that particulate matter increased earth's albedo (reflectance of solar irradiation), so that less solar energy penetrates to the surface (volcanic ash in the atmosphere has the same effect). Until recently these two opposing phenomena more or less balanced one another, but now the balance has clearly shifted and the "greenhouse effect" is leading to rapid global warming. Long-held meterological records the world over are being broken: 6 of the 7 hottest years on record have occurred since 1980; some years ago, the lowest low pressure zone ever recorded (hurricane Gilbert) in late summer was followed in the next winter by the highest high pressure area ever measured during recorded history. These are not random events, but are almost certainly direct consequences of human-induced changes in the atmosphere.
Desertification has been greatly accelerated during the past century due to above-mentioned processes, too. Arid areas are in a more precarious and perilous position than wetter areas. As the human population burgeons, the last remaining natural habitats are rapidly being destroyed. Earth's atmosphere is being altered at an ever increasing rate, leading to rapid weather modification. Global warming is having its impact on virtually all plants and animals, including humans, and its effects will continue to intensify into the forseeable future.
Crop failures would seem to be inevitable. People have lost touch with nature -- many seem to have forgotten where food comes from -- some people may think that boxes of Triscuits grow on supermarket shelves. But empty shelves in supermarkets will eventually awaken people to the dire danger of tampering with earth's atmosphere -- however, by then it will be much too late to rectify the situation. People will be appalled that scientists cannot restore the atmosphere to its former condition. But, there can be no quick "technological fix" for earth's much maligned atmosphere. The continuing existence of all the denizens of this poor beleaguered planet, including ourselves, will ultimately depend more on our ecological understanding and wisdom than it will on future technological "advances."
Unlimited cheap clean energy, such as that so ardently hoped for in the concept of cold fusion, would actually be one of the worst things that could possibly befall humans. Such energy would enable well-meaning but uninformed massive energy consumption and habitat destruction (i.e., mountains would be levelled, massive water canals would be dug, ocean water distilled, water would be pumped and deserts turned into green fields of crops). Heat dissipation would of course set limits, for when more heat is produced than can be dissipated, the resulting thermal pollution would quickly warm the atmosphere to the point that all life is threatened, perhaps the ultimate ecocatastrophe.
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Last updated 25 October 2004 by Eric R. Pianka