Section 19.4 (Exam 3)

Question 1

What does natural selection act on?

Answer 1

The phenotype, not directly on the genotype

Question 2

Define fitness.

Answer 2

Reproductive contribution of a phenotype to subsequent generations relative to other phenotypes

Question 3

Define qualitative traits.

Answer 3

influenced by alleles at only one locus (e.g., smooth vs. wrinkled)

Question 4

Define quantitative traits.

Answer 4

show continuous variation ; influenced by alleles at more than 1 locus

Question 5

What are the three ways that natural selection can act on quantitative traits?

Answer 5

Stabilizing selection

Directional selection

Disruptive selection

Question 6

Define stabilizing selection. How does it affect variation in a population?

Answer 6

Average phenotypes are selected

Reduces variation but does not change the mean

Question 7

Define directional selection.

Answer 7

When individuals at one extreme are more successful

Question 8

Define disruptive selection. How does it affect variation in a population?

Answer 8

Individuals at either extreme are more successful than average individuals

Variation in a population is increased