4/17/24 - Lecture 11: Natural Selection III: Patterns and Constraints on Natural Selection

Question 1

Directional selection

Answer 1

Entire bell curve shifts to the left or right

Phenotypes at one extreme have the highest fitness

Question 2

Stabilizing selection

Answer 2

Bell curve is squeezed

Average phenotypes have the highest fitness, reduction in variance over time

Question 3

Disruptive/stabilizing selection

Answer 3

Bimodal distribution

Phenotypes at either extreme have the highest fitness. Results in an increase in trait variance

Question 4

Intra-sexual selection

Answer 4

Male-male/female-female competition

Question 5

Inter-sexual selection

Answer 5

One sex is ‘choosy’

Question 6

What should happen with the sex that invests more in reproduction?

Answer 6

It is selected to be more selective

Question 7

What should happen with the sex that invests less in reproduction?

Answer 7

It is selected to compete for mates

Question 8

Constraints on evolution by natural selection

Answer 8

If heritability is zero
Tradeoffs
Laws of physics (can’t get too big)
Evolutionary history (can’t make immediate big changes)