EOC_ch05

Essential Environment: The Science behind the Stories (3rd Edition)

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Chapter 5 Testing Your Comprehension 1 Natural selection rests on the premises that more individuals are born into a population than will survive to reproduce; that variation exists within the population; that some of that variation both affects survival and reproduction and is heritable; and that Earth is ancient. Because we know each of these premises to be true, then individuals with favorable characteristics will be more likely to reproduce and pass the genes for those favorable traits along to the next generation in greater abundance. 2 Examples of evidence for natural selection include the human breeding of domesticated animals, human selective breeding of crop plants, and laboratory experiments with fast-breeding species such as fruit flies, as well as evidence from numerous evolutionary studies of the natural world, including those on organismal adaptations. 3 When a population is split into two populations that become geographically and reproductively isolated from each other, they may evolve over time, in their different environments and under different selective pressures, into different species. This is called allopatric speciation. 4 The golden toad has apparently gone extinct, probably due to the effects of climate change and possibly disease on an isolated mountaintop population. The passenger pigeon was driven to extinction by market hunting, after many of its forests had been cleared. The last of the dinosaurs went extinct,
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This document was uploaded on 10/30/2010.

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EOC_ch05 - Chapter 5 Testing Your Comprehension 1 Natural...

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