Lecture 13: Fitness and Selection (Exam 2)

Question 1

Why it appears evolution can be “goal directed” and how we know it’s not

Answer 1

• organisms appear as if they were designed, and sometimes nonsensical
• organisms cannot predict future conditions and change their own genes to ensure their survival

Question 2

What makes natural selection nonrandom and what happens if traits are positively or negatively (or not) correlated with reproductive success

Answer 2

• it only works by births + deaths of individuals overtime
• the correlation between trait and reproductive success is **not zero **
• if a trait positively correlates, the genotype frequency increases in population
• if a trait negatively correlates, genotype frequency decreases in population

Question 3

biological fitness

Answer 3

a quantitative measure of reproductive success relative to others in a population

Question 4

selected for

Answer 4

• nothing is “actively” selecting anything
• traits providing an advantage in survival & reproduction in an abiotic & biotic context can be “selected for”

Question 5

5 assumptions of Hardy-Weinberg Equilibrium

Answer 5

1. infinite population size
2. no mutation
3. no selection
4. no migration
5. random mating

Question 6

How we model selection mathematically

Answer 6

• through HWE
• mathematically account for more of a certain genotype than expected

Question 7

modes of selection and patterns they produce

Answer 7

• directional selection: single phenotype favored
• stabilizing selection: average phentoype value best
• disruptive selection: extreme values favored

Question 8

frequency-dependent selection

Answer 8

• frequency of trait in the population affects its fitness

Question 9

How selection interacts with drift or mutation and the patterns produced when different genotypes have higher fitness than others

Answer 9

??? watch video

Question 10

the cases in which we observe allele frequencies achieving equilibrm

Answer 10

??? watch video