Chapter 21

Chapter 21 - Chapter 21 Evidence and Mechanism of Evolution...

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Chapter 21: Evidence and Mechanism of Evolution 21.1 – What facts form the basis of our understanding of Evolution? o Darwin made a trip in 1831 to the Galapagos islands where he noted that the species of finches were similar but different from those off of South America o Using these observations he came up with an evolutionary theory that stated that: Species are not immutable, they change over time Divergent species share a common ancestor The mechanism that produces changes in species is natural selection o Natural selection is the differential survival and reproduction of individuals in a population based on the variations in their traits. o Darwin said species were related to each other through common descent o Alfred Russel Wallace wrote a similar description of natural selection 4 years before Darwin o Darwin and Wallace are were influenced by Malthus o Darwin suggested that since not all animals reproduce as often or as much as they are able, then there are slight variations among individuals that affect the chance that it will survive and reproduce o Artificial selection is the controlled breeding of plants and animals with desirable traits o Individuals do not evolve, populations do o A population is a group of individuals of a single species that lice and interbreed in a particular geographic area at a particular time o Evolutionary adaptation refers both to the process of adapting new characteristics and the new characteristics as well Adaptive processes are the evolutionary mechanisms that produce adaptive traits Adaptive characteristics are the new traits created by the adaptive processes that would help an organism survive and reproduce o Biologists can say that an organism has adapted if there is a slightly different organism in the same environment that survives less well
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o Genetic links for Darwin were nonexistent due to population genetics not existing because it was discovered by Mendel in the 1930’s o When concepts of evolution joined with population genetics, the a new understanding of evolutionary biology called Modern Synthesis emerged o For a population to evolve, its individuals must have heritable genetic variations o We do not see these genetic variations unless they result in different phenotypes o Features of phenotypes (e.g. eye color) are called characters
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Chapter 21 - Chapter 21 Evidence and Mechanism of Evolution...

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