Chapter 19 Key Terms - Principles of Biology

Assortative mating

When individuals tend to mate with those who are phenotypically similar to themselves

Bottleneck Effect

magnification of genetic drift as a result of natural events or catastrophes

Cline

Gradual geographic variation across an ecological gradient

Directional Selection

Selection that favors phenotypes at one end of the spectrum of existing variation

Diversifying Selection

Selection that favors two or more distinct phenotypes

Evolutionary Fitness

Individual’s ability to survive and reproduce

Founder Effect

Event that initiates an allele frequency change in part of the population, which is not typical of the original population

Frequency-Dependent Selection

Selection that favors phenotypes that are either common (positive frequency-dependent selection) or rare (negative frequency-dependent selection)

Gene Flow

Flow of alleles that the individuals in the population carry

Genetic Drift

Effect of chance on a population’s gene pool

Genetic Structure

Distribution of the different possible genotypes in a population

Genetic Variability

Diversity of alleles and genotypes in a population

Good Genes Hypothesis

Theory of sexual selection that argues individuals develop impressive ornaments to show off their efficient metabolism or ability to fight disease

Handicap Principle

Theory of sexual selection that argues only the fittest individuals can afford costly traits

Honest Signal

Trait that gives a truthful impression of an individual’s fitness

Inbreeding Depression

Increase in abnormalities and disease in inbreeding populations

Microevolution

Changes in a population’s genetic structure

Modern Synthesis

Overarching evolutionary paradigm that took shape by the 1940s and scientists generally accept today

Nonrandom Mating

Changes in a population’s gene pool due to mate choice or other forces that causes individuals to mate with certain phenotypes more than others

Population Genetics

Study of how selective forces change the allele frequencies in a population over time

Population Variation

Distribution of phenotypes in a population

Relative Fitness

Individual’s ability to survive and reproduce relative to the rest of the population

Selective Pressure

Environmental factor that causes one phenotype to be better than another

Sexual Dimorphism

Phenotypic difference between a population’s males and females

Stabilizing Selection

Selection that favors average phenotypes