Chapter 3: Forces of Evolution Flashcards

Questions and Answers

Define: Breeding Population.

A group of organisms that tend to choose mates from within the group.

Define: Hardy-Weinberg Equilibrium.

An outdated mathematical statement whereby, in the absence of nonrandom mating and evolutionary forces, genotype and allele frequencies will remain the same from one generation to the next.

Define: Evolutionary Forces.

Four mechanisms that can cause changes in allele frequencies from one generation to the next: mutation, natural selection, genetic drift, and gene flow.

What are the four forces of evolution?

Mutation, natural selection, genetic drift, and gene flow. Signup and view all the answers

Define: Nonrandom Mating.

Patterns of mate choice that influence the distributions of genotype and phenotype frequencies. Signup and view all the answers

Define: Inbreeding.

Mating between biologically related individuals. Signup and view all the answers

Define: Fitness.

An organism's probability of survival and reproduction. Signup and view all the answers

Define: Balancing Selection.

Selection for the heterozygote and against the homozygotes (the heterozygote is the most fit). Signup and view all the answers

Define: Stabilizing Selection.

Selection against extreme values, large or small, in a continuous trait. Signup and view all the answers

Define: Directional Selection.

Selection against one extreme in a continuous trait and/or selection for the other extreme. Signup and view all the answers

Define: Genetic Drift.

A mechanism for evolutionary change from the random fluctuations of gene frequencies from one generation to the next. Signup and view all the answers

Define: Founder Effect.

A type of genetic drift caused by the formation of a new population by a small number of individuals. Signup and view all the answers

Define: Gene Flow.

A mechanism for evolutionary change resulting from the movement of genes from one population to another. Signup and view all the answers

Define: Genotype Frequency.

The measure of the relative proportions of different genotypes within a population. Signup and view all the answers

Define: Allele Frequency.

The measure of the relative proportions of different alleles within a population. Signup and view all the answers

What has the greatest evolutionary effect on small populations?

Genetic drift. Signup and view all the answers

In what ways may a harmful allele not be eliminated from a population?

The heterozygote could carry on the allele, new mutations could bring it back, and the recessive allele may be beneficial. Signup and view all the answers

Study Notes

Breeding Population

Group of organisms that preferentially mate within their own group.

Hardy-Weinberg Equilibrium

Mathematical principle stating that in the absence of evolutionary forces, allele and genotype frequencies remain stable across generations.

Evolutionary Forces

Four mechanisms influencing allele frequency changes:
- Mutation
- Natural selection
- Genetic drift
- Gene flow

Nonrandom Mating

Mating patterns that affect genotype and phenotype distributions.

Inbreeding

Occurs when related individuals mate, potentially increasing homozygosity.

Fitness

The likelihood of an organism’s survival and ability to reproduce successfully.

Balancing Selection

Favors heterozygotes over homozygotes, ensuring the most fit genotype.

Stabilizing Selection

Eliminates extreme phenotypes in a continuous trait, favoring intermediate values.

Directional Selection

Favors one extreme phenotype over the other in a continuous trait.

Genetic Drift

Changes in allele frequencies due to random sampling effects, more pronounced in small populations.

Founder Effect

Type of genetic drift that occurs when a new population is established by a small number of individuals, leading to reduced genetic variation.

Gene Flow

Transfer of genetic material between populations through migration, affecting allele frequencies.

Genotype Frequency

Relative proportion of different genotypes in a population.

Allele Frequency

Relative proportion of various alleles present within a population.

Impact of Genetic Drift

Genetic drift has the most significant effect on small populations, leading to potential loss of genetic variation.

Persistence of Harmful Alleles

Harmful alleles may persist due to:
- Heterozygotes carrying the allele
- New mutations reintroducing it
- Potential beneficial effects of recessive alleles.

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Description

Test your understanding of key terms and concepts related to the forces of evolution with these flashcards. Learn about breeding populations, Hardy-Weinberg equilibrium, and other fundamental ideas that shape evolutionary biology.