Lecture 15: Sexual Selection and Co-Evolution Flashcards
What are maladaptive traits?
Traits that may not be beneficial for the survival aspect of fitness
What is sexual selection?
The mate preferences of one, or both, sexes drives evolution
What are primary sexual characteristics?
Differences in the biological sexes directly related to reproduction (e.g. genitalia, ovaries)
What are secondary sexual characteristics?
Traits which are used in sexual selection,
but are not required for sexual reproduction (e.g. horns, pretty feathers, etc)
What are thw two main types of sexual selection?
Intrasexual selection: within the same sex
Epigamic (intersexual) selection: between sexes
Explain intrasexual selection.
Direct competition between two members
of the same sex for the opposite sex –> Most often seen as male to male competition
for a female who has limited choice in mate selection
Explain epigamic (intersexual) selection.
Selective pressure from the member of one sex having complete choice over a mate of the opposite sex –> display or courtship to attract members of the opposite sex (usually when both individuals help raise the offspring)
How does dimorphism affect sexual selection?
When males do not stay to help raise the offspring: Males are often much more colorful
and smaller/same size than females (extreme sexual ornamentation)
Where males help raise offspring: both sexes are often the same color and size
T or F: Most common type of epigamic selection is female of the species having primary choice in mates.
True! While male choice does exist, it is much rarer.
What does resource intensity have to do with selection selection?
Males don’t typically care so much: sperm is low input and high output, success comes from mating with as many females as possible, meaning the male can afford to select a suboptimal mate.
Females do typically care more: Eggs are high energy investment and are a fixed number, pregnancy is energy intensive, reproductive success comes from breeding with the BEST male and costly to choose poor mate.
What is bateman’s principle?
The sex which invests the most in producing offspring will become a limiting resource over which the other sex competes.
What is the fischerian runaway selection hypothesis?
Female prefer a secondary sexual characteristic –> female selects that mate, then passes that secondary character to her male offspring and also passes on a genetic trait in her daughters to desire that secondary sexual characteristic –> creates a positive feedback, increases the desirability and extreme nature of the character over generations.
What is the sexy son hypothesis?
Females choose attractive mates because it means that their own male offspring will be better able to attract mates
What is the handicap hypothesis?
Extreme secondary sexual characteristics indicate that the individual can afford to waste resources on developing the secondary sexual characteristic and still survive making it a good mating choice.
What is reproductive isolation?
When more elaborate sexual practices and structures leads to more common changes in preference
What is coevolution (aka reciprocal evolution)?
Where two (or more) species impact each other’s evolution.
What is the evolutionary symmetric arms race?
Two species whose interactions result in them co-developing the same trait (ex: only tallest trees get sunlight so all tree species evolve to grow taller)
What is the asymmetrical evolutionary arms race?
Both species are co-evolving, however the selection pressure acting on the two species is different (ex: cheetah evolving speed but gazelle evolving endurance)
What is mutualism?
Interactions between two different species mutually benefit each other
What is parasitism?
Interaction between two different species where one benefits at the expense of the other (highly destructive) –> finely tuned to preserve host’s life
What are brood parasites?
Animals that rely on others to raise their young: cuckoo finch lays its eggs in other’s nests.
