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Study Questions:
5) How can the environment influence the expression of a trait?
6) How can the environment influence the VALUE of a trait? Relate this to Darwin's idea of the divergence of populations in different environments.
7) Why are most lethal alleles recessive? Answer with respect to the effects of selection on a dominant, deleterious gene.
8) As such, how can a dominant lethal allele be maintained in a population?
9) How does the particular type of sex determination in turtles, by temperature,
maximize reproductive success in
a harem-forming species?
10) Explain why females are often larger than males, even in species in which individuals change sex.
11) Consider this cross: AaXBY x AaXBXb
- How many types of gametes can the male make with respect to these loci? (answer: 4)
- How many phenotypes are possible in the progeny (Assume IA and complete dominance for both loci).
Answer: 2 at "A", 3 at "B" (B females, B males, and b males) = 6.
- What fraction of male offspring will express the Ab phenotype? 3/4 A x 1/2 b. (only 1/2 the SONS) = 3/8
12) Why is sexual reproduction adaptive?
13) Why are multiple sexes adavantageous in populations with low rates of dispersal?
14) How might a multi-sex system have evolved into a two-sex system as a consequence of cytoplasmic wars?