The main idea
Microevolution occurs by means of changes in allele frequency, and that happens in five major ways. Natural selection is only one of these.
Describe microevolution and the Modern Synthesis that made this view possible.
- Microevolution is a change in the gene pool of the population. Evolution occurs at small scales by changes in gene frequencies
- Therefore, a population is the minimum unit that can evolve
- Darwin's ability to describe how evolution worked was limited because he did not know the mechanism for inheritance. The modern synthesis is this view of evolution that includes population genetics. This allows us to make testable predictions of how evolution might proceed
Define the Hardy Weinberg Equilibrium, the conditions necessary for its existence and how it relates to five modes of evolution.
- Hardy Weinberg Equilibrium (HWE) is a “null model” of no evolution within a population, i.e. allele frequencies remain constant through generations and requires certain conditions to be met.
- Microevolution occurs in any case that breaks the rules of HWE (*=most typical causes)
Describe three potential results of natural selection on the pattern of variation in a population, and give an example of each.
Explain how natural selection depends on variation, and why it cannot produce "perfect" organisms
- Selection is an editing process, and therefore requires variation in the gene pool. Lack of variation limits ability to adapt to changing environment
- Variation is generated by mutation and sexual recombination; not all variation is subject to selection (= neutral variation)
- Variation is maintained by diploidy and balancing selection
- Selection cannot fashion perfect organisms because: limits on existing variation, historical constraints, compromises among adaptations and because chance, natural selection and the environment interact
- Perpetuation of genes constitutes evolutionary fitness
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