Evolution of Populations

Flashcards about evolution of populations, microevolution, allele frequencies, and agents of microevolution.

What is Microevolution?

Change in allele frequency in a population

What is a population?

Group of individuals of the same species that live in the same area and interbreed with each other significantly more often than they interbreed with individuals from a different population

What is exclusion breeding?

Consistent interbreeding among individuals of a population to the near exclusion of individuals in another population. The ranges of those two populations could overlap while the genetic compositions remain distinct.

What is the frequency of an allele?

Measure of how common a particular allele is in the population in comparison to all other alleles for the same gene

What does it mean when an allele is fixed in the gene pool?

When the frequency of the allele = 1.0. All members of the population are homozygous for that particular gene.

What does it mean when an allele is lost or extinct from the gene pool?

When frequency = 0.0. It is not present in the gene pool.

What are the three major ways in which allele frequencies change in a population?

Genetic drift (differential survival of alleles and random loss of alleles), gene flow (gain of alleles and loss of alleles), and natural selection (differential survival of alleles).

What is genetic drift?

Random change in allele frequency in a population as a result of chance

How does genetic drift affect adaptive traits?

Unlikely to facilitate the spread of adaptive traits. Adaptive traits have no better chance of persisting and spreading in the population that any other trait.

How does genetic drift affect small populations?

The effects of genetic drift are exaggerated.

What two processes result in small, homogenous populations in which genetic drift will have substantial effect on allele frequencies?

The founder effect and the bottleneck effect.

What is gene flow?

The movement of alleles or genes between one or more populations of the same species.

How does gene flow affect gene pools of linked populations?

The populations that are linked through gene flow tend to become more genetically similar.

When does gene flow increase?

It increases as the distance between populations decreases; as population size increases or population density increases.

How does natural selection alter reproductive success?

Causes differential reproductive success among individuals, resulting in an overrepresentation of some traits/alleles in future generations at the expense of others.

What is relative fitness?

Defined as the contribution of a specific genotype to the next generation compared to the contribution of the most fit genotype for the same gene in a single population.

What is the selection coefficient (s) used for?

Quantify the frequency reduction in reproductive success (reduced fitness) of less fit genotypes in comparison to the most fit genotype.

What is balancing selection?

The phenomenon in which selection preserves genetic variation by maintaining two or more phenotypes in a population.

What is an example of heterozygote advantage?

Persons heterozygous for the sickle-cell allele gain immunity from malaria but do not suffer the full effect of sickle cell disease. Heterozygotes have an advantage over both homozygotes where malaria is common.

What is frequency-dependent selection?

The fitness of a genetic variant or genotype depends on how commonly the variant or genotype occurs in the population.

What is a mutation?

Change in nucleotide sequence in an organism’s DNA or RNA

How do mutations effect fitness?

Advantageous mutations increase fitness, deleterious mutations decrease fitness and neutral mutations have no effect on fitness.

What is non-random mating?

Mates for sexual reproduction are selected based on one or more criteria.

What are the two major forms of non-random mating?

Sexual Selection and Inbreeding