Lecture 8: Natural & Sexual Selection Flashcards
natural selection
-the only adaptive evolutionary force
adaptation
-a natural change that allows an orgnism to either survive better, or reproduce more
adaptive
-adaptiveness isnt the cause of natural selection events
selective forces defintion
-environmental factors which may reduce reproductive success in a population and thus contribute to evolutionary change or extinction through the process of natural selection
selective forces examples
- predation
- parasitism
- climate factors
- mate attraction
- resource acquisition
fitness
- quantified
- the # of offspring that survive into the next generation
absolute fitness
-the total # of surviving offspring that an individual produces during its lifetime
relative fitness
-the # of offspring in ratio to the highest possible # of offspring
stabalizing selection
- stabilizes the populations variation around the best version of the trait(ends up being the mean)
- ex: birth weight
directional selection
- when the environment changes
- mean always changes
disruptive seleciton
- selection for both ends of the trait range and against the avg trait value
- most important for speciation
balancing selection
- selection actively works to maintain multiple alleles or phenotypes in the population
- ways it works is through heterozygote advantage and negative frequency dependent selection
heterozygote advantage
-heterozygote has a higher fitness than either of the 2 homozygotes
negative frequency dependent selection
-the fitness of a genotype dec. when its frequency in the population becomes higher
reproductive strategy examples
- mate choice
- mating frequency
- mate guarding
- parental care
- long-term mating behavior(monogamy vs. polygyny)
- offspring spacing
parental investment
- men invest less to mate
- for women, the after effects of mating can be very costly so they’re cautious
what happens when a male and female parental investment is equal or males invest more?
-partner choice are done cautiously by both men and female
female choice
-they choose whoever wins male/male/competition
male/male competition
-can be physical or more of a portrayal of appearance of dominance
sexual dimorphism
-distincting btwn male and female animals
parental care
-looking for good fathers, resource protection, good genes (oldest, largest, healthiest)
territory defense and resource acquisition
-good for when she raises her kids
good genes hypothesis
- females look for good genes
- old males: successful in surviving, getting food, resisting parasites
- health: denoted as good size, diet, thus less likely to have a disease
handicap principle hypothesis
- applies to organisms that have display characteristics that’re hard to maintain
- males show off characters that are a handicap to their survival/success
runaway selection
- women choose something about the other animal that probably once showed good health but is now a handicap but they still choose them
- “ghost of selection past”
- i.e. long tailed widowbird
what is an example of directional selection?
- salmon
- selective pressure (humans) lower the mean weight by keeping higher weighted salmon
what is an example of disruptive selection?
- colonial bentgrass
- grows in soil heavily contaminated with metals and is resistant to metals
- grass farthest away is also thriving
what is an example of sexual dimorphism?
- males are a lot larger
- males have specialized structures for fighting
what is an example of a reproductive strategy?
- austrailian riflebirds
- the males had a dance to show off to females in hope to mate
