Microevolution III: Natural Selection Flashcards
selection is a blend of what
chance(mutations) and sorting
how do new genetic variants arise
chance through mutations and sexual recombo
define sorting
favored alleles are passed on to next gen, deleterious ones are removed
define adaptations
traits that have evolved through mechanisms of NS
strong selection = ?
weak selection = ?
faster change in allele freq
slower change in allele freq
when does adaptive evolution occur
when the match between an indiv and env inc
t/f: adaptive evolution is a continuous process
t
directional selection
one ptypic extreme is favored
changes mean value of a character over time
shift trait freq
disruptive selectiond
favors both extremes of ptype range
stabilizing selection
favors intermediate trait
homogenizes and stabilizes pop, status quo, dec variation,
closer to mean of original pop
define relative fitness
contribution of a gtype to the next gen compared to contributions of other indivs
most fit gtype in population: W =1
define selection coefficient
measure of relative intensity of selection against a given gtype
s = 1-w
selection on dominant allele
W11 = W12 > W22
freq inc rapidly, slow to remove recessive allele
selection on incomplete dominance
as # of gens go by, selection quickly favors allele
W11>W12>W22
selection on recessive allele
takes long time to inc freq of rec allele
at very low freq most of recessive alleles are in heterozyg so are hiding but conce crosses threshold and selection acts quickly
