The Ways of Change 4C (notes)

Question 1

What determines the probability of fixation in genetic drift?

Answer 1

1. The alleles initial frequency in the population
2. Remember- with genetic drift a population will eventually become fixed for one allele or another.

Question 2

Genetic drift is random as it occurs as

Answer 2

as a result of pure chance

Question 3

However, selection on an inbred population may have different results than on a random-mating population, since selection acts on genotypes. The most drastic case is heterozygote advantage.

Question 4

Evolution is often a compromise between natural selection and sexual selection. The trait that confers mating advantage to the male increases his evolutionary fitness because he will mate with more females. However, the same trait (the peacock’s tail, for example) may be a serious liability when he has to escape from predators. It may seriously shorten his lifespan. So, the fitness advantage of the trait (mating with more females) must offset the survival disadvantage (shortened lifespan), or sexual selection would not continue.

Question 5

The more complex the feature, the more likely

Answer 5

any kind of overlap is due to a common evolutionary past.

Question 6

Homologous structures share a similar —; analogous organs have a similar —

Answer 6

• embryonic origin
• function