Evolution and Sex III

Question 1

Define sexual selection.

Answer 1

differential reproductive success due to variation among individuals in success at getting mates

Question 2

Since females are typically limited by number of eggs and males by number of mated, should sexual selection be more important in driving phenotypic evolution in males or females?

Answer 2

Males

Question 3

What is male competition?

Answer 3

When males fight for females

Question 4

What is female choosiness?

Answer 4

Females pick the “best” males

Question 5

What are the two general types of selection?

Answer 5

Intersexual
Intrasexual

Question 6

What is intersexual selection?

Answer 6

o When one sex exercises choice over their mates of the opposite sex
o Usually females choosing males because of asymmetry in costs of sex, but role reversals exist

Question 7

What is intrasexual selection?

Answer 7

o When mates of the same sex compete with one another to gain access to mates
o Usually involves some form of male-male competition

Question 8

What are the five hypotheses for intersexual selection?

Answer 8

Good genes hypothesis
Run-away selection hypothesis
Direct benefits hypothesis Sensory bias hypothesis
Sexual conflict hypothesis

Question 9

Describe the good genes hypothesis.

Answer 9

Sexual selection acts on traits that represent an indirect signal of the genetic quality of the male mate, and thus whether offspring will inherit “good genes”

Question 10

Give examples of signals of good genes.

Answer 10

o Song
o Colour
o Displays

Question 11

Good genes for what?

Answer 11

o Resisting parasites
o Avoiding predators
o Maintaining top physical and physiological condition

Question 12

Describe the run-away selection hypothesis.

Answer 12

• The genetic control of female preference is genetically linked to the genes controlling the male trait females prefer
• Over time this can lead to increasing and increasing exaggeration of the trait

Question 13

Give an example that seems to follow the run-away selection hypothesis.

Answer 13

Long tails in widowbirds

Question 14

Describe the direct benefits hypothesis.

Answer 14

that increase the female’s survival and fecundity

Question 15

Give examples of direct benefits.

Answer 15

o Food
o Protection from predators
o Territories/nests
o Help raising young

Question 16

Describe the sensory bias hypothesis.

Answer 16

• Males evolve traits that exploit existing sensory biases in females
• The evolved traits provide no indicator of a male’s quality

Question 17

Give examples of sensory biases.

Answer 17

o Colours associated with favourite foods
o Behaviours for capturing food or avoiding predators

Question 18

Describe the sexual conflict hypothesis.

Answer 18

• Traits that evolve in one sex are detrimental to individuals of the other sex, leading to sexual conflict
• Sexual conflict can drive antagonistic coevolution of male and female traits

Question 19

What are some sources from which sexual conflict can arise?

Answer 19

o Predation risk
o Food acquisition
o Territory size
o Multiple paternity

Question 20

List the two forms of post-copulatory sexual selection.

Answer 20

Sperm competition
Female choice

Question 21

What is sperm competition?

Answer 21

Ejaculates from multiple males compete within female reproductive tract for access to eggs

Question 22

What is female choice?

Answer 22

Ability of females to affect the likelihood of sperm from a particular male fertilizes their eggs