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Species become extinct. In fact, in the long history of Earth (about 4.5 billion years) most species have become extinct. The fossil record (see How We Know) shows what many extinct animals and plants were like. These life forms have never come back. Are we next? Extinction occurs when drastic changes occur in climate or living conditions. A given species may or may not be adapted, for life under the changed conditions. About the same time that extinction occurs, new species appear to take their place. New species typically have a genetic make-up that allows them to take advantage of the changed life conditions. New species appear because they happen to be adapted to the changed conditions.
Science and EvolutionWe are talking here about evolution. Scientists also have evidence for evolution of the universe.
Scientists use theories
Absolute proof for a theory is not necessary. A theory deserves support as long as it remains useful and cannot be disproved through experimental evidence. No theory in biology meets these requirements better than the theory of evolution. In "modern" times, ideas about evolution were first introduced around 1865 by Charles Darwin and Alfred Wallace. When they found out about each other's work, Darwin and Wallace decided to publish at the same time. But it was not evolution that they discovered. What they discovered was how evolution occurred. Talk about evolution has always created religious arguments. In the time of Darwin and Wallace, people who thought evolution made sense were subject to vicious ridicule and condemnation as evil people. Both Darwin and Wallace were shy and reclusive and avoided public controversy. It took an aggressive champion, Thomas Huxley, to speak out on evolution. Huxley convinced the scientific world that the Theory of Evolution was correct. His story is the subject of our Story Time.
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Introduction |
Why It Matters |
How We Find Out |
What We Know |
Story Time
Peer Curriculum |
Ecosystems Home Page |
Communication Exercises
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