Evolution, Speciation, and Reproductive Barriers Lecture Review

Flashcards covering key vocabulary from the lecture on evolution, speciation, and reproductive barriers, including concepts like natural and sexual selection, gene flow, the biological species concept, and different isolation mechanisms.

Natural Selection

The only process that causes organisms to become better adapted to their environment over time by accumulating alleles for heritable traits that enhance survival and reproduction.

Sexual Selection

A form of natural selection where individuals with certain inherited characteristics are more likely to obtain mates, often pushing populations in opposite directions to natural selection, as seen in guppy spot size.

Genetic Drift

Random changes in allele frequencies within a population, operating at all times alongside natural and sexual selection, especially in isolated populations.

Adaptation (process)

The accumulation of traits that are beneficial for a particular environment in a population over time through natural selection.

Adaptation (trait)

Any one of the traits that is beneficial for a particular environment, which can be entirely contextual (e.g., polar bear's white fur).

Gene Flow

The input of alleles from adjacent populations, often through the migration of individuals or gametes, causing changes in allele frequencies unconnected to genetic drift or natural/sexual selection.

Macroevolution

Evolution at or above the species level, involving the formation of new evolutionary lineages, largely focused on processes leading to new species.

Speciation

Any process that leads to the formation of new species.

Biological Species Concept

A species is defined as a group of populations whose members have the capacity to interbreed under natural conditions and produce viable and fertile offspring.

Viable Offspring

Offspring that are alive, can develop, and produce actual offspring.

Fertile Offspring

Offspring that can have babies of their own and reproduce.

Horizontal Gene Transfer (HGT)

The transfer of genes across lineages, even unrelated ones, through processes like viruses or endosymbiosis, disconnected from usual sexual reproduction.

Prezygotic Barriers

Reproductive barriers that prevent fertilization from happening.

Postzygotic Barriers

Reproductive barriers that arise or maintain after fertilization happens, affecting the viability or fertility of hybrids.

Habitat Isolation

A prezygotic barrier where individuals from different populations live in different environments, preventing them from meeting to mate (e.g., islands vs. mainland).

Temporal Isolation

A prezygotic barrier where individuals are awake or reproductively active at different times (e.g., nocturnal vs. diurnal, different breeding seasons).

Behavioral Isolation

A prezygotic barrier where different mating behaviors or rituals prevent individuals from recognizing each other as mates).

Mechanical Isolation

A prezygotic barrier where physical parts, such as reproductive organs, do not fit together, preventing successful mating (e.g., snail shell coiling, insect genitalia).

Gametic Isolation

A prezygotic barrier where gametes (sperm and egg) are not chemically compatible with each other, preventing fertilization even if mating occurs.

Reduced Hybrid Viability

A postzygotic barrier where hybrid offspring fail to develop normally and often die before completing development.

Hybrid Sterility

A postzygotic barrier where hybrid offspring develop normally but are infertile and unable to reproduce themselves (e.g., mules).

Hybrid Breakdown

A postzygotic barrier where the first-generation hybrids are robust, but subsequent generations (F2, F3) experience genetic difficulties, incompatibilities, and reduced viability or fertility.

Allopatric Speciation

Species divergence that occurs due to a physical or geographical barrier separating populations ('different homelands').

Sympatric Speciation

Species divergence that occurs in the absence of a physical barrier, with populations remaining in the same homeland or territory.