Classification-07-web

Classification-07-web - Evidence for Evolution 1 The...

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Evidence for Evolution The Diversification of Life: Evidence for Evolution We can make a series of predictions based on Darwin’s theory of evolution. If these predictions are correct, then the evidence supports Darwin’s theory: Prediction 1: There should be evidence of extinction. Last time, I discussed the 5 mass extinction events as well as the phenomenon of background extinction. The most recent episode of mass extinction is happening right now. Although it is difficult to compare fossil extinction rates to present extinction rates, some estimates of current human-mediated extinction put extinction rate at 1000 to 10000 times above “background”. Here are some interesting facts: 11% of 9040 known bird species endangered. 4000 U.S. plant species are of conservation concern, with 680 of 20,000 U.S. plant species expected to be extinct by end of this year. (The most rapid loss of habitat is not in the rain forest, but in the coastal chaparral of Southern California.) 20% of freshwater fishes in the world have either gone extinct in the last few hundred years or are endangered, with 40 species going extinct in the U.S. over the last century. 31,000 plant and animal species are endangered worldwide, with as many as 1/5 of all species going extinct in the next 30 years. In short, extinction is a reality, and Darwin’s Theory of Evolution predictions that there should be much evidence of extinction in the fossil record. However, we’re not quite sure why there have been periods of mass extinction. Prediction 2: There should be evidence of transitional (or intermediate) forms in the fossil record. To illustrate transitional form, let’s once again consider the case of the dinosaurs. You’ve already heard me say that some dinosaur species have modern descendants that we call birds, but what is the evidence for this supposition? After all, dinosaurs and birds look quite different! The evidence comes from the fossil record. First, recent fossil digs in China that have revealed well-preserved fossils that clearly show that some dinosaurs had feathers. But this is only a small part of the argument. A more important part of the argument is the species called Archaeoptoryx . I want you to remember two things: 1) Archaeopteryx fossils have a few characteristics like those of modern birds that most dinosaurs (and sometimes all dinosaurs) did not have. 2) Archaeopteryx fossils display many traits in common with dinosaurs. 1
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Evidence for Evolution Because Archaeopteryx contains many features of birds AND dinosaurs, it is an organism that represents the transition from birds to dinosaurs. In Darwin’s time, the lack of transitional fossils was one of the problems with his argument with evolution. However, over the last 140 years paleontologists have uncovered a multitude of transitional fossils. Other examples include whales and horses. Notes about transitional forms in the fossil record #1)
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Classification-07-web - Evidence for Evolution 1 The...

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