Evolution 2: Gene Flow, Speciation, & Macroevolution

Vocabulary flashcards covering gene flow, species concepts, reproductive isolation, modes of speciation, macroevolution concepts, and notable examples from the lecture notes.

Gene flow

The movement of alleles among populations, via movement of individuals or reproductive structures (e.g., pollen, seeds), which can introduce new variation into a population.

Gene pool

The aggregate of all alleles present in all individuals within a population.

Natural selection

Differential survival and reproduction of individuals based on heritable traits, leading to adaptive change in the population.

Sexual selection

A form of natural selection where traits affecting mating success are favored, often contributing to reproductive isolation.

Artificial selection

Human-driven selection of traits in a population.

Genetic drift

Random fluctuations in allele frequencies due to chance events, often reducing genetic variation.

Mutation

Random changes in DNA that create new alleles; the raw material for evolution.

Microevolution

Small-scale evolution within a population, involving changes in allele frequencies.

Macroevolution

Large-scale evolution above the species level, including patterns like speciation and extinction.

Speciation

The process by which new species arise through the evolution of reproductive isolation and divergence.

Biological species concept

A group of interbreeding natural populations that can produce viable, fertile offspring in nature; defined by reproductive compatibility.

Morphological species concept

Species defined by structural features and morphology.

Ecological species concept

Species defined by occupying a unique ecological niche.

Phylogenetic species concept

Species defined by evolutionary history and common ancestry (shared evolutionary lineage).

Reproductive isolation

Barriers that prevent gene flow between populations, leading to the formation of different species.

Prezygotic barriers

Barriers that prevent mating or fertilization before a zygote is formed.

Habitat isolation

Populations inhabit different habitats, reducing encounters and mating opportunities.

Temporal isolation

Mating occurs at different times or seasons, preventing interbreeding.

Behavioral isolation

Differences in mating behaviors or signals that prevent interbreeding.

Mechanical isolation

Incompatibilities in reproductive anatomy that prevent mating or transfer of gametes.

Gametic isolation

Gametes are unable to unite or fertilize due to biochemical incompatibilities.

Postzygotic barriers

Barriers after fertilization that reduce the viability or fertility of hybrids.

Reduced hybrid viability

Hybrids have lower survival rates or die before reaching maturity.

Reduced hybrid fertility

Hybrids are sterile or have greatly reduced fertility.

Hybrid breakdown

First-generation hybrids may be viable/fertile, but subsequent generations have reduced viability or fertility.

Allopatric speciation

Speciation driven by geographic separation that leads to reproductive isolation and divergence.

Sympatric speciation

Speciation occurring within the same geographic area, often via habitat differentiation, sexual selection, polyploidy, or behavioral changes.

Polyploidy

Having more than two sets of chromosomes; a common mechanism of instant speciation in plants.

Habitat differentiation (sympatric mechanism)

Populations diverge by occupying different habitats or microhabitats, leading to reproductive isolation.

Sexual selection (sympatric mechanism)

Divergence driven by mate preferences within a shared area, contributing to speciation.

Mimulus color genetics

In Mimulus (monkey flowers), two genetic loci determine flower color, influencing pollinator preference and reproductive isolation.

Euhadra snail shell direction (single-gene)

Direction of shell spiral controlled by a single gene, affecting mating compatibility and isolation.

Pollinator-driven speciation

Speciation driven by shifts in pollinator attraction or visitation (e.g., hummingbirds vs bees) leading to reproductive isolation.

Punctuated equilibrium

Speciation occurs relatively rapidly, with long periods of little evolutionary change in between.

Gradualism

Slow, steady evolutionary change over long time scales.

Proponents of punctuated equilibrium

Mayr; Eldredge & Gould, who argued for rapid bursts of speciation with stasis in between.

Anagenesis

Evolutionary change within a single lineage without branching into separate lineages.

Rate of speciation timescale

Intervals between speciation events can range from ~4,000 years to ~40 million years, averaging around 6.5 million years.