lecture 20 Flashcards
what is fitness and what impacts it?
relative genetic contribution of individuals to next gen
it results from the diff in viability and fertility
its relative measure to how much beter/worse individuals/genotypes are at surviving + reproducing compared to other pops
what is selection and how does it impact genetic/allele frequency?
some individuals are better adapted to certain enviros and have higher fitness
all else being equal we wld expect more of there genes in next gen
what’s the diff b/w natural and artifical selection?
artificial selection is done because of human goals, human get to choose who gets to reproduce and how much, natural selection is done due to abiotic and biotic enviro factors which doesn’t have a goal
ex. droughts don’t happen because enviro is trying to select for drought resistant plants
what is stabilizing selection and how does it impact phenotype frequency? what is an example of this type of selection?
under stabilizing selection individuals w/ values closer to mean will have survival/reproductive advantage
it will act against distribution extremes and favors individuals in the center
will reduce variant/spread of trait values in pop
ex. baby birth weight, birth canal is fixed width
what is disruptive selection and how does it impact phenotype frequency? what is an example of this type of selection?
it favours extreme values like rlly big/rlly small, rlly fast/rlly slow
favours extremes and acts against middle
it creates greater variaiton/wider distribution
ex. african finches are bimodal either have wide beaks food for hard seeds or narrow beaks good for soft seeds
what is directional selection and how does it impact phenotype frequency? what is an example of this type of selection?
it favours of the extremes and will change mean of the distribution/pop
ex. large beaks favoured in finches after drought and so average beak size became larger
what knowledge do we lack abt natural selection/what makes natural selection difficult to 100% prove?
we lack convincing cases where we know the mechanism/agents of natural selection
ex. we can show bigger rabbits have higher survival rate, but we can’t show why
demoing natural selection is easy, but demoing why is difficult
in what cases can selection be easily demonstrated and explained?
when agents of selection for evolution are man-made like pollution it becomes easier to in reason for selection
ex. black moths during industrial era britain
in what cases can selection be easily demonstrated and explained?
when agents of selection for evolution are man-made like pollution it becomes easier to in reason for selection
ex. black moths during industrial era britain
ex. metal contamination in plants
why don’t all organisms evolve resistance to the same thing in the same area?
resistance might be costly to have, so if its unneeded, for example only part of the area is contaminated by metal then only that part of the plants will selected to have resistant genotypes
