bio120 test 1

tangled bank hypothesis

genetic variation beneficial in spatially heterogenous environments

red queen hypothesis

genetic variation beneficial in temporally heterogenous environments

outcrossing

occurs in hermaphrodite species, occurs when they mate with other individual

selfing (self-fertilization)

occurs in hermaphrodite species; mating with yoursel

population genetics effects of inbreeding

• changes in genotype frequencies

• decreases heterozygosity

• no change in allele frequencies or polymorphism

why does selfing in hermaphrodites have a transmission advantage

because it doubles to copy of genes for the next generation (ovule + pollen

reproductive system vs. sexual system vs. mating system

(asexual, sexual) vs. (dioecious, hermaphrodite) vs. (cross-fertilization, self-fertilization)

stochastic evolutionary forces

mutation, recombination, genetic drift

neutral theory of selection

• negative selection rapidly eliminated

• positive selection rapidly fixed

• most mutations are selectively neutral

polymorphism

• proportion of gene loci that have 2 or more alleles in the population

• polymorphic without being heterozygous

heterozygous

fraction of individuals that are heterozygous out of all gene loci

classical school

• less fit types reintroduced by mutation

• followed by selection acting to remove them

• low heterozygosity / polymorphism

balance school

• heterozygote advantage

• frequency-dependent selection

• fitness varies in space or time

• high heterozygosity / polymorphism

are genetic differences between flies adaptive?

Non-synon. substitutions are ~10x more likely to become fixed than synonymous ones

gene flow

movement of alleles from one population to another

factors that influence genetic variation

1) mutation

2) recombination

3) genetic drift

4) natural selection

5) gene flow

genetic drift

changes in frequency of existing gene variant due to random chance

3 types of natural selection

negative (purifying)

positive (directional)

diversifying

types of selection for continuous traits

stabilizing

directional

disruptive

gene flow

movement of genetic material from one population to another

gene flow influence on differentiation vs genetic variation

decrease differences between populations, increase genetic diversity/variation