Need for biodiversity

When a species is commercially important and goes extinct, its loss can be assigned a dollar value. Atlantic cod, American mahogany, and great auks are listed by the IUCN Red List as Vulnerable, Endangered and Extinct species respectively. All are or were harvested commercially, and all could be ascribed some worth by the industries that made use of them. Such large organisms as whales, tigers, bison, and manatees are mammalian megafauna that, while not commercially important, hold symbolic or aesthetic values for humans. But what about the lower metazoans, the species described in this volume of Grzimek's? Most people would not know that an ophiuoroid is related to a sea star or that as-cidians in their early life possess a structure very like a human notochord, let alone value these organisms. "Priapulan" is harder to pronounce than to describe, but few people will have even seen the word. Loriceferans were described for the first time in 1983 as resembling tiny "ambulatory pineapples." People might realize that sea cucumbers do not improve either the taste or the appearance of garden salads, but if one refers to them as holothuroids, most will respond with blank stares. When the poor name recognition of some of the lower metazoans is combined with their lack of commercial value, the fact that some of their populations are close to the vanishing point makes their value seem questionable.

The loss of any species, however, goes beyond its monetary worth. Certainly the morality of allowing species, including many that have been evolving longer than humans have, to suffer extinction as the result of human interference is indefensible. But a more scientific and impartial reason to prevent extinction exists: biodiversity. First coined by E. O. Wilson in 1986, the term "biodiversity" refers to the sum of all diversity, all the variability in a given area that is genetic, conferred by other species, or inherent in the ecosystem itself. Simply put, biodiversity is the natural variability among living organisms and everything that fosters that variability.

From a strictly anthropocentric standpoint, humans have benefited directly and greatly from biological diversity. Penicillin comes from the mold Penicillium sp. The tree Calophyl-lum lanigerum was found to produce a substance that inhibits replication in the AIDS virus. Aequorin, collected from the jellyfish Aequorea victoria, is a common fluorescent marker used in medicine and microbiology. Studies of the venom of a South American pit viper led to the discovery of the an-giotensin system that regulates human blood pressure. Venom from marine cone snails has given rise to a synthetic analgesic and is used to keep nerve cells alive following ischemia. The compound cytarabine is more effective at inducing remission in one form of leukemia than any other drug. The polymerase chain reaction (PCR), a technique that revolutionized the field of microbiology, was made possible because of an enzyme discovered in a bacterium in the hot springs of Yellowstone, Wyoming. PCR enables us to perform rapid DNA testing of criminal suspects. It allows microbiologists to modify the genomes of bacteria, insert specific genes into them, and ultimately produce genetic modifications of other plants and animals. The thermophilic bacteria found in those hot springs are more similar to bacteria found at hydrothermal vents in the deep sea than to common bacteria like Escherichia coli; scientists have classified them in their own kingdom, Archaea.

As we find new organisms or look more closely at familiar ones, we discover more human uses for those organisms. This fact underscores the very tangible benefits to humans of conservation—even if it is based on aesthetic values, as was the inception of Yellowstone National Park over a century ago. Moreover, conservation offers emphatic demonstrations of the value of biological surveys because scientists continue to find new organisms even at the most general level of classification, the animal kingdom.

Yet even species that have no present or apparent commercial use benefit humans in ways that are taken for granted. Processes as fundamental as natural selection and evolution depend on genetic variability. Plants require nitrogen to grow. Although nitrogen is the largest single component of the air humans breathe, most plants cannot use it in its stable atmospheric form N2. Some bacteria and blue-green algae help to "fix" atmospheric nitrogen into forms that can be used by plants. Different species of bacteria form different types of nitrogenous byproducts. Some bacteria are even endosymbi-otic and live in the root tissues of legumes. As organisms die and then decompose into their elemental components— mostly water, carbon, nitrogen and some minerals—which are eventually recycled, the very mechanics of nutrient and energy transfer are dependent upon a diversity of plant and animal species. Humans do not ascribe a monetary value to such ecosystem services as decomposition, carbon, or nitrogen cycling. They are, however, invaluable because life as we know it would not exist without them.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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