Chapter 21: Mechanisms of Evolutionary Change

What is defined as change in populations of organisms over time?

Evolution

True or False: Evolution happens at the individual and not the population level

False

What is genetic variation?

presence of difference alleles of genes in a population

The result of any process that changes the genetic composition of a population over time…

evolution

Morphology, genes, proteins, and genomes can all be used to study…

variation

What is polymorphic variation?

many different alleles in a population

Phenotype is a result of _______ and the environment

genotype

What are the mechanisms of evolution?

mutation, gene flow, genetic drift, selection, nonrandom mating

What is mutation

any change in the base sequence of DNA

What is the ultimate source of variation?

mutation

How common are mutations and are they the primary cause of changes in allele frequency?

rare, no

What is the movement of alleles from one population to another?

gene flow

How does gene flow impact allele frequency?

shifts frequency

• new alleles become introduced

What is defined as the change in allele frequencies due to sampling error (random chance)

Genetic drift

Where does genetic drift have the largest effect?

small populations

given sufficient time, genetic drift can cause substantial ______ to allele frequencies

changes

• alleles will drift to fixation or loss

• heterozygous decline

What is the founder effect?

new population is established by a small number of individuals it is unlikely that they carry all the alleles in the present population

What is the bottleneck effect?

small amount of individuals are contributing gametes to the next generation, alleles might not represent parent population

What describe the idea that the number of offspring an organism leaves behind is affected by phenotype and behavior?

selection

What i the primary mechanism of evolution?

natural selection

What are the conditions for natural selection?

variation, differences in survival and reproduction, heritability

What is the process that occurs when environmental conditions affect which individuals produce the most offspring?

natural selection

Evolutionary forces can _____ __________

work together

What is artificial selection?

process of human selecting for characteristics, selective breeding

What does fitness refer to?

combination of survival, mating success, # of offspring/mating

What does selection favor?

phenotypes with the greatest fitness

What does Hardy Weinberg determine?

proportion of genotypes in a population if evolutionary forces are not present

What is required to meet Hardy-Weinberg Equilibrium?

1) no mutation takes place

2) no genes are transferred to or from other sources

3) mating is random

4) the population size is very large

5) no selection occurs

How is H-W equilibrium used?

predict allele frequency for populations

population genetics

how selective forces change a population through changes in allele and genotypic frequencies

As the heritability of a population’s phenotypic variation increases, what else increases?

susceptibility to evolutionary forces

Nonrandom mating

individuals chose their mates nonrandomly, females may have a preference

What is sexual selection?

acts on traits that increase an organism’s ability to obtain mates

What are cases of genetic drift?

bottleneck effect, founder effect