Evolution and Natural Selection (Chapters 14–16)

Vocabulary flashcards covering key terms and concepts from lecture chapters 14–16 on evolution and natural selection.

Evolution

A change in allele frequencies within a population over generations, leading to diversification of species.

Allele Frequency

The proportion of a specific allele among all alleles for a given gene in a population.

Mutation

A change in the DNA sequence that creates new alleles and is the ultimate source of genetic variation.

Genetic Drift

Random changes in allele frequencies due to chance events, especially in small populations.

Bottleneck Effect

Genetic drift resulting from a drastic reduction in population size caused by disasters, disease, or over-hunting.

Founder Effect

Loss of genetic variation when a small group breaks off from a larger population to establish a new one.

Migration (Gene Flow)

Movement of individuals (and their alleles) between populations, altering allele frequencies in both.

Natural Selection

Differential survival and reproduction of individuals with heritable traits that are better suited to the environment.

Variation

Differences in traits among individuals of a population, supplying raw material for natural selection.

Heritability

The ability of a trait to be passed genetically from parents to offspring.

Differential Reproductive Success

The tendency of individuals with advantageous traits to leave more offspring than others.

Fitness

The relative reproductive output of an individual compared to others with alternative phenotypes in the same population.

“Survival of the Fittest”

Phrase summarizing that individuals with higher fitness contribute more genes to future generations.

Adaptation (Process)

The evolutionary process by which populations become better suited to their environments through natural selection.

Adaptation (Trait)

A heritable feature that increases an organism’s fitness in a particular environment.

Fixation

Point at which a single allele reaches 100 % frequency in a population’s gene pool.

Biological Species Concept

Definition of species as groups of naturally interbreeding populations that are reproductively isolated from others.

Reproductive Isolation

Set of barriers preventing gene flow between populations, leading to separate species.

Prezygotic Barrier

A reproductive barrier that prevents mating or fertilization between species (e.g., courtship differences, gamete incompatibility).

Postzygotic Barrier

A reproductive barrier that reduces viability or fertility of hybrid offspring (e.g., sterile mules).

Hybrid

An offspring resulting from mating between two closely related species.

Speciation

The evolutionary process by which one ancestral species splits into two or more descendant species.

Allopatric Speciation

Formation of new species following geographic isolation of populations.

Geographic Isolation

Physical separation of populations by barriers such as mountains, rivers, or distance, preventing gene flow.

Sympatric Speciation

Speciation occurring within the same geographic area, often driven by sexual selection or niche differentiation.

Adaptive Radiation

Rapid diversification of a lineage into many species, typically when new resources or habitats become available.

Mass Extinction Event

A period when extraordinarily high numbers of species disappear in a relatively short geologic time.

Fossil Record

Chronological collection of preserved remains and imprints used to trace evolutionary history.

Geochronology

Study of the age of earth materials; sediment layers reveal fossil succession and increasing complexity over time.

Intermediate Species

Transitional fossils, such as Tiktaalik, showing traits of two major groups and evidencing evolutionary links.

Homologous Structures

Anatomical features in different species that share a common ancestry, e.g., mammalian forelimb bones.

Vestigial Structure

A remnant feature that no longer serves its original function (e.g., human wisdom teeth).

Comparative Embryology

Study of embryo development revealing shared structures (gill pouches, tails) that imply common ancestry.

Molecular Biology Evidence

Similarities in DNA and protein sequences across species supporting common descent.

Antibiotic Resistance

Evolution of bacterial populations that survive drugs due to natural selection for resistant alleles.

Gene Flow

Exchange of genes between populations via migration, counteracting differentiation.

Fitness Depends on Environment

Relative reproductive success of a phenotype varies with specific environmental conditions (e.g., fur color vs. habitat).

Founder Effect in Amish

High frequency of extra digits in Amish due to small founding population carrying the allele.

Adaptive Landscape

Concept that populations navigate changing environmental ‘pressures,’ never reaching perfect optimization.

Five Lines of Evolutionary Evidence

Fossil record, biogeography, comparative anatomy & embryology, molecular biology, lab/field experiments.