| The New Dictionary of Cultural Literacy, Third Edition. 2002. |
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| Life Sciences |
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| The study of living things on the Earth has a long history. Because of the incredible richness and diversity of life, most of the effort in biology and in its predecessor, natural history, has been expended on an effort to describe what there is—simple exploration and cataloguing. The classical sciences of descriptive botany and zoology, with their emphasis on classification, are examples of this sort of work. The division of living things into the plant kingdom and animal kingdom (plus three more kingdoms added by modern scientists to describe microscopic organisms and fungi), and the collection of all living things into a coherent classification scheme, are the fruit of this work. During the past century and a half, however, two important discoveries have changed the face of the life sciences. | 1 |
| The first of these was the development of the theory of evolution by Charles Darwin and others. The mechanism of natural selection gave naturalists for the first time a way of answering questions about how life came to have the forms it has, rather than just questions about what those forms are. The great social and intellectual turmoil triggered by Darwin’s work is interesting, of course, but is not relevant from a purely scientific standpoint. What does matter is that we can now understand how the observed diversity of living things could have arisen through the action of a simple and easily comprehended mechanism. The original Darwinian notions have been modified and expanded since his time, of course, and there is still debate about the pace at which species evolve. Nevertheless, the main principle of Darwinism—that living things change and adapt in response to their environment—has been incorporated as one of the pillars of the modern life sciences. | 2 |
| The second great change in the life sciences is the shift from studying organisms as a whole to studying the complex chemical processes inside the cell, both in its everyday workings and in reproduction. This change can be symbolized by the discovery of the structure of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in the 1950s and the completion of the Human Genome Project in 2000. | 3 |
| The new emphasis on basic biochemistry has had several consequences. For one thing, the realization that genetic information is passed from one generation to the next through DNA has filled in the Darwinian picture of the development of life. Natural selection acts when individuals of the same species differ, but until recently we had no notion of why these differences occurred. Now, thanks to modern genetics, this missing piece of the Darwinian picture is being filled in. | 4 |
| A detailed understanding of the working of the individual cell, the basic building block of life, is also beginning to emerge. We see the cell as a system in which information is carried and stored in DNA and RNA molecules, but in which the actual work is done by an assembly of proteins. Most of the details of the cell’s working are too complex to be included in our list, but it is important to be aware that these secrets are being unraveled. It is hard to imagine modern cancer research progressing, for example, without consideration of what makes a cancer cell different from a normal one. At the same time, our knowledge of genetic processes makes it possible for us to cure hereditary diseases and to create living things that never existed in nature. We can produce life forms to help improve the human condition, much as our ancestors developed domestic livestock thousands of years ago. This field remains one of the most vital and exciting areas of research in modern science. | 5 |
| While some life scientists are examining the smallest parts of living organisms, others are studying the complex interrelationships of communities of plants and animals. The new science of ecology aims at understanding the way that living systems (including human beings) interact with one another and with their environment. The scope of such studies can extend from a small marsh to the entire planet. —J.T. | 6 |
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| | | The New Dictionary of Cultural Literacy, Third Edition. Edited by E.D. Hirsch, Jr., Joseph F. Kett, and James Trefil. Copyright © 2002 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. |
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