22.Evolutionary Theory

22.Evolutionary Theory - What is meant by `evolution'?...

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1 Evolutionary Theory What is meant by ‘evolution’? • Biologists use the term to mean a change in the frequency of alleles in a population through time/generations. – Alleles are the forms that the genes can take (red eye vs. white eye fruit flies=two alleles) • Most people use it to mean the mutation of living organisms through time to produce new species (this is what biologists refer to as speciation). Micro vs. Macro • Microevolution is when evolution takes place within a species –e.g. the breeding is dogs and pidgeons • Macroevlution is when evolution goes far enough to produce a new species (this is also referred to as speciation). What is ‘natural selection’? • 1) Excess of offspring • 2) Scarcity of resources results in competition • 3) Variation (intraspecies and interspecies) produces differential dying which creates divergence • 4) Inheritance; the individuals that survive more often will pass on their traits with a greater proportion to the next generation than those with lower survival rates • Requires mutation and particulate inheritance Natural Selection • Evolution is the process, Natural Selection is a mechanism to explain how it happens. • Herbert Spencer first said “Survival of the Fittest” and Darwin borrowed the phrase, but it is tautological.
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2 Sewall Wright’s “adaptive landscape” What is ‘genetic drift’? • Even without selective pressures the frequency of alleles in an interbreeding population may shift over time. • Shifts are easier and more drastic in small populations than large. • Genetic bottlenecks produce an extreme. • Kurt Vonnegut’s book Galapagos is an excellent example of a genetic bottleneck. ‘Punctuated equilibrium’? • Large populations remain static, and evolution is most efficient when it is occurring in small peripheral isolates. • Small populations cut off from main populations will tend to diverge “quickly” from the parent stock. • Populations can be isolated from each other by
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This note was uploaded on 04/16/2008 for the course SYGN 101 taught by Professor Shorey during the Spring '08 term at Mines.

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22.Evolutionary Theory - What is meant by `evolution'?...

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