Evolution of Populations Lecture Notes

A set of vocabulary flashcards covering the concepts of speciation, population genetics, Hardy-Weinberg equilibrium, and natural selection based on Alexandra Kukova's lecture notes.

Allopatric speciation

Speciation occurring through geographical separation where a physical barrier stops populations from interbreeding, causing groups to change drastically over time.

Sympatric speciation

Speciation occurring through ecological and behavioral separation within the same geographic area.

Polyploidy

A condition common in plants where an organism has more than two complete sets of chromosomes.

Tetraploidy

An organism with four sets of chromosomes that is sterile but can still grow and divide via mitosis; it is theoretically a new species because it cannot interbreed with its diploid parent.

Prezygotic Isolation

Reproductive isolation mechanisms that occur before a zygote is formed, such as mismatching mating behaviors, physical inability to mate, or gametic incompatibility.

Postzygotic Isolation

Reproductive isolation mechanisms that occur after a zygote has formed, resulting in non-viable offspring or viable but sterile offspring, such as a mule.

Population

A localized group of individuals that is capable of interbreeding and producing fertile offspring.

Microevolution

The change in genetic makeup from generation to generation, representing evolution over a few generations.

Modern Synthesis

The integration of many different fields of study, such as statistics and botany, into the study of evolution.

Gene Pool

The collection of all alleles at all loci of a population; in other words, all the genes of a given population.

Hardy-Weinberg Theorem

The principle that frequencies of alleles and genotypes in a population gene pool will remain constant from generation to generation if only Mendalian segregation and recombination of alleles are at work.

p

The variable representing the frequency of the dominant allele in a population; in the provided example, $p=0.8$ for the $C^R$ allele.

q

The variable representing the frequency of the recessive allele in a population; in the provided example, $q=0.2$ for the $C^W$ allele.

Hardy-Weinberg Equilibrium Equation

The mathematical formula $p^2+2pq+q^2=1$ used to determine genotype frequencies in a non-evolving population.

Genetic Drift

Fluctuation in allele frequency based on finite population size and chance rather than natural selection.

Bottleneck Effect

A type of genetic drift where a sudden change in the environment reduces population size, leaving survivors that are not reflective of the original gene pool.

Founder Effect

A type of genetic drift that occurs when individuals become isolated from a population and establish a new population in a new area.

Gene flow

The movement of traits resulting from genetic additions or subtractions from a population, such as pollen moving from one island to another.

Phenotypic Polymorphism

The existence of two or more distinct morphs represented in a population in highly notable frequencies.

Average heterozygosity

The average number of heterozygous loci in a population, calculated as the number of heterozygous loci divided by total loci.

Geographic variation

Differences in the gene pools of separated populations, such as those divided by a mountain range.

Clines

A graduated change in a trait along a geographic axis, such as plant height changing based on altitude.

Fitness

The contribution an individual makes to the gene pool of the next generation; a value of $1$ means the next generation is entirely composed of that individual's traits.

Directional Selection

Selection that occurs when environmental change or migration shifts the frequency curve of phenotypes toward one extreme.

Disruptive Selection

Selection that favors variants at both extremes of the distribution while removing intermediate phenotypes.

Stabilizing Selection

Selection that removes extreme variants from the population and favors intermediate phenotypes.

Sexual Selection

Natural selection specifically for mating success.

Intrasexual Selection

Selection involving competition within the same sex, such as males fighting males for the right to breed.

Intersexual Selection

Often called mate choice, this occurs when individuals of one sex (usually females) are choosy in selecting their mates.