Natural Selection Probability Models

Name:

Date:

📚 Part 1: Probability & Hardy-Weinberg

1. In a large population under Hardy-Weinberg equilibrium, allele a has frequency q = 0.7. What is the expected frequency of homozygous aa individuals?

0.09

0.21

0.49

0.30

2. If p = 0.6 and q = 0.4 in a population of 1,000 individuals, how many heterozygotes (2pq) do you expect?

240

480

360

600

3. A dominant allele B confers higher survival than allele b (B fitness = 0.8, bb fitness = 0.5). Which allele is expected to increase in frequency over generations?

Neither — frequencies stay the same

Cannot tell without population size

4. If allele A frequency is 0.2, what is the probability that two random gametes produce a heterozygote offspring (2pq)?

0.04

0.16

0.32

0.64

5. In a small population the allele X frequency is 0.10. If two gametes combine at random, what is the probability at least one gamete carries allele X?

0.01

0.09

0.19

0.81

6. Which condition is required for allele frequencies to remain constant (Hardy-Weinberg equilibrium)?

Random mating and no selection

Small population size

Strong directional selection

High migration between populations

📊 Part 2: Selection & Sampling Models

7. A shell color allele has frequency 0.25. If you sample 8 offspring, what is the probability exactly 2 carry that allele? (Use binomial probability)

0.11

0.31

0.50

0.78

8. Light-colored mice survive predation at 30% while dark-colored mice survive at 90%. Starting with a light-allele frequency of 0.4, what is the most likely short-term outcome for the light allele?

Its frequency will decrease

Its frequency will increase

Frequency will remain the same

Frequency will change only due to mutation

9. If p = q = 0.5, what is the probability that a random offspring is homozygous (either AA or aa)?

0.25

0.50

0.75

1.00

10. If the probability an individual is homozygous is 0.5, what is the probability that in a sample of 4 offspring all are homozygous?

0.0625

0.125