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Evolution, Diversity& Phylogeny Practice Problems Will an extremely rare, beneficial allele have a better chance of fixing in a very large population, or in a very small population? Explain your answer. What are the four forces of evolution? Which evolutionary forces increase genetic diversity? Which decrease diversity? List Darwin's postulates? If these are NOT fulfilled, can evolution occur? 1. 2. 3. 4. The A and B genes are closely linked on an autosome). Gene D resides on a separate autosome. Draw these chromosomes, and their alleles, in a 2n cell with unreplicated chromosomes whose genotype is: 5. AB Dd ab If two, or four crossover (recombination) events occur between genes A and B, will you see the results of those events in the gametes? What if one (or three, or five) occur: will you see the results then? Draw a cell whose chromosomes have crossed over twice between genes A and Draw that cell in Metaphase I of Meiosis. B 6. 7. In a population of birds, if beak depth is not variable, can it evolve via natural selection? Why or why not? Which of Darwin's postulates are verified by this data from a population of finches? 11.0 ” E 10.0 9.0 '억 8아 s.0 9.0 11.0 Midparent bill depth, mm (Futuyma 1998)

Answer 1

• 1. Larger populations pave the path for arousal of many rare beneficial alleles.
• If a rare mutation creates an extremely rare beneficial allele, it gets fixed through positive selection.
• If there is random genetic drift, the rare beneficial allele gets lost up.
• Heterozygosity decreases and homozygosity increases in genetic drift.
• Deleterious mutant alleles get fixed up in smaller populations.
• Founder effect could be seen in smaller populations.
• Founder effect results in reduced genetic diversity.

1. If founder carries the rare beneficial allele, as in larger populations, it spreads up.