Population Genetics

Population

A group of individuals of the same species living in a specific area that interbreed.

Microevolution

Small-scale evolutionary changes that occur within a population. (Ex. antibiotic resistance)

Macroevolution

Large-scale evolutionary changes that occur over geologic time, involving the emergence of new species. (Ex: dinosaurs to birds)

Evolutionary biologists care about variation because

it is essential for natural selection and adaptation

Deleterious Trait

A trait that decreases an organism's fitness, reducing survival and reproduction.

Character

A heritable feature that varies among individuals (Ex: bill size)

Trait

A specific characteristic of an organism (Ex: small bill or big bill)

Gene Pool

The total collection of alleles in a population

Allele Frequency

The proportion of a specific allele among all allele copies in a population (p and q, A and a)

Locus

A specific location on a chromosome where a gene or alleles are found.

Genotype Frequency

How often we see a specific allele combo (p² and q²)(AA, Aa, aa)

Population Genetics

The study of genetic variation within populations and how it changes over time

An equation expressing the relationship between allele frequencies in a population under the Hardy-Weinberg principle

p + q = 1

Hardy-Weinberg Assumptions

No mutations, random mating, no gene flow, infinite population size, and no selection

Deviation from Hardy-Weinberg Predictions

If allele or genotype frequencies differ from predictions, it means that evolutionary forces are acting on the population (Ex: natural selection, genetic drift, gene flow, mutation, or non-random mating)

Factors Changing Allele Frequencies

natural selection, genetic drift, mutation, and gene flow

Mate Choice

Selection of a mate based on certain traits or characteristics

Assortative Mating

A form of mate choice where individuals with similar phenotypes mate more frequently

Genetic Drift

Random changes in allele frequencies that have a more significant effect in small populations

Population Bottleneck

A sharp reduction in population size due to environmental events, leading to a loss of genetic diversity

Founder Effect

Reduced genetic diversity that occurs when a small number of individuals establish a new population

Gene Flow

The transfer of genetic variation from one population to another

Adaptation

The process by which a species becomes better suited to its environment through changes in traits

Example of gene flow

A bee carrying its pollen to one species of flowers to another

Examples of genetic drift

founder effect, bottleneck effect