Evolution – Core Concepts (Herrick)

Vocabulary flashcards covering key terms and definitions from Evolution lecture notes.

Evolution

A change in the frequency of alleles or genotypes in a population over time.

Genetic variation

Differences in DNA sequences among individuals.

Allele frequencies

The frequency of an allele in a population, calculated as copies of that allele divided by total allele copies.

Allele

A variant form of a gene at a given locus.

Genotype

The pair of alleles an individual has for a gene locus (e.g., BB, Bb, bb).

Phenotype

The observable traits of an organism resulting from the genotype.

Gene pool

All the alleles present in all individuals in a species.

Population

An interbreeding group of organisms of the same species living in the same geographic area.

Locus

The location of a gene on a chromosome.

Loci

The plural form of locus.

Hardy-Weinberg Equilibrium

A model describing allele and genotype frequencies in a non-evolving population; assumes no differential survival, no migration, no mutation, large population, and random mating.

p (allele frequency)

The frequency of the dominant allele for a gene in a population (p + q = 1).

q (allele frequency)

The frequency of the recessive allele for a gene in a population (p + q = 1).

p^2

Predicted frequency of the homozygous dominant genotype (BB) under HW.

2pq

Predicted frequency of the heterozygous genotype (Bb) under HW.

q^2

Predicted frequency of the homozygous recessive genotype (bb) under HW.

Natural selection

Process where individuals with certain heritable traits produce more offspring, increasing those traits in the population.

Fitness

The extent to which a genotype is represented in the next generation.

Migration

Gene flow; movement of individuals that can change allele frequencies.

Mutation

A change in DNA that can create new alleles; a nonadaptive evolutionary mechanism.

Genetic drift

Random fluctuations in allele frequencies, especially in small populations.

Nonrandom mating

Mating that is not random (e.g., mate choice, inbreeding) and can affect genotype frequencies.

Molecular evolution

Change in DNA or amino acid sequences over time.

Molecular clock

Concept that molecular changes accumulate at different rates across species, used to estimate evolutionary time.

Sexual selection

Selection related to mating success; can be due to competition or mate preference.

Intrasexual selection

Competition within the same sex for mates.

Intersexual selection

Mate choice by one sex for mates of the other sex.

Directional selection

Pattern where selection shifts the population mean in one direction.

Stabilizing selection

Pattern that favors intermediates, reducing variation.

Disruptive selection

Pattern that favors extreme phenotypes, disfavors intermediates.

Artificial selection

Directional selection driven by humans (breeders) rather than natural processes.

Dominant allele

An allele that is expressed in the phenotype of both homozygotes and heterozygotes.

Recessive allele

An allele expressed only in homozygotes.

Observed allele frequencies

The actual measured frequencies of alleles in a population.

Predicted genotype frequencies

Genotype frequencies (p^2, 2pq, q^2) predicted by Hardy-Weinberg from allele frequencies.

p + q = 1

In Hardy-Weinberg, the sum of allele frequencies for a gene equals 1.

Measurement methods for variation

Observable traits, gel electrophoresis (gene size), and DNA sequencing (sequence data).