Lec 11: Sexual Selection and Co-evolution Flashcards
What is a maladapted trait? Give an example.
A trait which is detrimental to fitness. Ex: the peacock’s tail
fitness is a function of …
survival and reproductive success
what are primary sexual characteristics?
differences in the biological sexes directly related to REPRODUCTION
What are secondary sexual characteristics?
traits used in sexual selection, but that are not REQUIRED for sexual reproduction
Name the 2 main types of sexual selection
- intrasexual selection
- epigamic selection
How can you tell that a male will not stay to raise the children after epigamic selection?
- the male is more colorful
- the female is larger
Why do females chose males?
- sperm is not a limiting factor, unlike ovaries
- pregnancy requires a high energy investment
What are physical indicators of intrasexual selection?
sexual dimorphism:
- males larger
- males have sexual ornaments
- males and females are of similar color
Which type of sexual selection is most common in species where both individuals raise the children and couple are monogamous?
epigamic selection
How can you tell that the male will help raise the children in epigamic selection
the male and female are of similar size and color
In males, reproductive success comes from…
mating with as many females as possible
in females, reproductive success comes from…
breeding with the BEST male
according to Bateman’s principle, which sex will become a limiting resource over which the other sex competes?
the sex which invests the most in producing offspring (not necessarily females)
Explain how, according to the Fischerian Runaway Selection Hypothesis, the desirability and extreme nature of maladaptive traits increase over generations.
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.
explain the sexy son hypothesis
females chose sexy mates so their son is also sexy so he attracts better mates
explain the handicap hypothesis
extreme secondary sexual characteristics demonstrate to the other sex that the individual can survive despite this handicap and is therefore a good mate
what is specific coevolution?
what is the most common type?
give 2 examples
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
distinguish asymmetrical and symmetrical arms race?
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
what’s the difference between obligate and facultative mutualism?
obligate = one of them would die without the other
facultative = they benefit from each other but they could survive without eachother
What are the different types of symbioses?
- 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.
What are the different types of coevolution?
- predator prey relationship
- symbioses (mutualism and parasitism)
- competition between species
