Ls 1 Lecture 5 (Agents Of Evolution)

Front 1

measuring variation can give u 3 types of frequencies, what are they

Back 1

allele frequencies
genotype frequencies
phenotype frequencies

Front 2

the frequences of alleles p and q

Back 2

# of certain allele / total alleles in population

Front 3

p+q=

Back 3

1

Front 4

hardy-weinberg equilibrium

Back 4

in the absence of selection or other agents that change the genetic makeup of the population, gene frequencies do not change over time

dominant alleles do not replace recessives

rare genes remain in populations

Front 5

hardy-weinberg equilibrium characterized by

Back 5

1. no selection
2. random mating
3. no differential immigration or emigratioin
4. large population
5. mutation rate low

Front 6

why is gene for sickle cell anemia so common?

Back 6

resistance to malaria in heterozygous state

Front 7

why do some recessive lethal alleles not disappear?

Back 7

rare, not selected against

Front 8

genetic bottleneck

Back 8

an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing, and the population is reduced by 50% or more, often by several orders of magnitude

ex: northern elephant seal
cheetah

Front 9

founder effect

Back 9

a small group becomes reproductively separated from the main population

galapagos finches

Front 10

directional selection

Back 10

selection for change
In population genetics, directional selection occurs when natural selection favors a single phenotype and therefore allele frequency continuously shifts in one direction.

Front 11

stabilizing selection

Back 11

selection against change

Put another way, extreme values of the character are selected against.

Front 12

disruptive selection

Back 12

selection against the average

Disruptive selection, also called diversifying selection, is a descriptive term used to describe changes in population genetics that simultaneously favor individuals at both extremes of the distribution.

Front 13

evolution can only work with ___

Back 13

what is present

ex: flight (birds used their arms, batsused their hands, pterosaurs used their fingers)

Front 14

extinction

Back 14

normal part of evolutionary process

most species that evolved are now extinct

history of life is one of adaptive radiations followed by mass extictions (mammalian dominance, dinosaur extinction)