chapter 11 bio

genetic variation

genetic variation

increases the chance that some individuals will survive

gene pool

genetic variation stored in a population

allele frequency (gene frequency)

each allele existing at a certain frequency

2 sources of genetic variation

Mutation - random change in organism’s DNA - form new traits, mutations in reproductive cells passed on, increase of genetic variation in gene pool

Recombination - new allele combination show up in offspring - most happens during meiosis

microevolution

observable change in allele frequency of a population over time

directional selection

causes a shift in populations phenotypic distribution - extreme phenotype that once was rare is now more common

stabilizing selection

the intermediate phenotype is favored and becomes more common - decreases genetic diversity - extreme phenotypes may be lost

disruptive selection

both extremes are favored and intermediate one selected against - intermediate forms selected against

gene flow

movement of alleles between populations - increases genetic variation - less can create genetically different populations and increases the chance that two populations will evolve into different species

genetic drift

change of allele frequencies due to chance - decreases genetic variations

bottleneck effect

genetic drift that occurs after an event

Founder effect

genetic drift that occurs after a small number of individuals colonize a new area

sexual selection

certain traits increases mating success - can promote and maintain novel genetic variation among individuals

Hardy - Weinberg equations

p² + 2pq + q² = 1

p + q = 1

what conditions must be met for a population to be in a Hardy Weinberg equilibrium

-large populations

-no emigration/immigration (no gene flow)

-no mutations (no new alleles added to the gene pool)

-random mating (no sexual selection)

-no natural selection (all traits must equally aid in survival)

what does it mean to be the same species

if they can breed together to produce offspring

speciation

the rise of 2 or more species from one existing species due to reproductive isolation

reproductive isolation

when members of same populations can no longer mate successfully with one another (they are then considered 2 different species)

Behavioral isolation

differences in courtship or mating behavior

Geographic isolation

involves physical barriers that divide populations

Temporal isolation

timing prevents reproduction between populations

convergent evolution

evolution towards similar characteristics in unrelated species

divergent evolution

related species evolve in different directions and become increasingly different

coevolution

two or more species evolve in response to changes in each other when both are benefiting

extinction

elimination of a species from earth

punctuated equilibrium

burst of evolutionary activity

adaptive radiation

diversification of one ancestral species into many descendant species