Lec 11: Sexual Selection and Co-evolution

Question 1

What is a maladapted trait? Give an example.

Answer 1

A trait which is detrimental to fitness. Ex: the peacock’s tail

Question 2

fitness is a function of …

Answer 2

survival and reproductive success

Question 3

what are primary sexual characteristics?

Answer 3

differences in the biological sexes directly related to REPRODUCTION

Question 4

What are secondary sexual characteristics?

Answer 4

traits used in sexual selection, but that are not REQUIRED for sexual reproduction

Question 5

Name the 2 main types of sexual selection

Answer 5

• intrasexual selection

- epigamic selection

Question 6

How can you tell that a male will not stay to raise the children after epigamic selection?

Answer 6

• the male is more colorful

- the female is larger

Question 7

Why do females chose males?

Answer 7

• sperm is not a limiting factor, unlike ovaries

- pregnancy requires a high energy investment

Question 8

What are physical indicators of intrasexual selection?

Answer 8

sexual dimorphism:

• males larger
• males have sexual ornaments
• males and females are of similar color

Question 9

Which type of sexual selection is most common in species where both individuals raise the children and couple are monogamous?

Answer 9

epigamic selection

Question 10

How can you tell that the male will help raise the children in epigamic selection

Answer 10

the male and female are of similar size and color

Question 11

In males, reproductive success comes from…

Answer 11

mating with as many females as possible

Question 12

in females, reproductive success comes from…

Answer 12

breeding with the BEST male

Question 13

according to Bateman’s principle, which sex will become a limiting resource over which the other sex competes?

Answer 13

the sex which invests the most in producing offspring (not necessarily females)

Question 14

Explain how, according to the Fischerian Runaway Selection Hypothesis, the desirability and extreme nature of maladaptive traits increase over generations.

Answer 14

1) Females prefer a secondary sexual characteristic.
2) Females selects mate with this characteristic.
3) passes that secondary sexual characteristic to her male offspring and ALSO passes trait to desire this trait to her female offspring.
4) creates a positive feedback loop.

Question 15

explain the sexy son hypothesis

Answer 15

females chose sexy mates so their son is also sexy so he attracts better mates

Question 16

explain the handicap hypothesis

Answer 16

extreme secondary sexual characteristics demonstrate to the other sex that the individual can survive despite this handicap and is therefore a good mate

Question 17

what is specific coevolution?
what is the most common type?
give 2 examples

Answer 17

specific coevolution occurs when two species reciprocally impact each other’s traits or genes.

most common type of specific coevolution is the evolutionary arms race

trees
cheetah & gazelle

Question 18

distinguish asymmetrical and symmetrical arms race?

Answer 18

symmetrical:

• pressure is the same on both species
• co-evolve the same trait
• ex: sunlight

asymmetrical:

• pressure is different (hunting vs evading)
• evolve different traits

Question 19

what’s the difference between obligate and facultative mutualism?

Answer 19

obligate = one of them would die without the other

facultative = they benefit from each other but they could survive without eachother

Question 20

What are the different types of symbioses?

Answer 20

• mutualism: both benefit from the other (facultative or obligate)
• parasitism: one species lives at the expense of the other (brood parasites). Fine-tuned relationship to preserve life of host.

Question 21

What are the different types of coevolution?

Answer 21

• predator prey relationship
• symbioses (mutualism and parasitism)
• competition between species