The Origin of Species - Speciation and Evolution

Flashcards covering key vocabulary related to speciation, reproductive barriers, species concepts, and evolutionary tempos from lecture notes.

Speciation

The process by which one species splits into two species, bridging microevolution and macroevolution.

Microevolution

Evolutionary change within a species or small group of organisms over a short period.

Macroevolution

The broad pattern of evolution above the species level.

Morphospecies

Organisms defined as a species based on very similar morphology or physical form.

Biological Species Concept

A population whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not with members of other such groups, based on reproductive compatibility.

Reproductive Isolation

Mechanisms that serve to isolate populations from other gene pools, preventing interbreeding and gene flow.

Reproductive Barriers

Mechanisms that prevent two species from producing fertile and viable offspring. They can be prezygotic or postzygotic.

Prezygotic Barriers

Reproductive barriers that block fertilization from occurring, acting 'before the zygote'.

Postzygotic Barriers

Reproductive barriers that contribute to reproductive isolation after the hybrid zygote is formed, acting 'after the zygote'.

Habitat Isolation

A prezygotic barrier where two species occupy different habitats within the same area, rarely encountering each other.

Temporal Isolation

A prezygotic barrier where species breed during different times of the day, different seasons, or different years.

Behavioral Isolation

A prezygotic barrier where unique courtship rituals or other behaviors prevent interbreeding, even between closely related species.

Mechanical Isolation

A prezygotic barrier where morphological differences prevent the successful completion of mating attempts.

Gametic Isolation

A prezygotic barrier where the sperm of one species cannot fertilize the eggs of another species, or cannot survive in the reproductive tract.

Reduced Hybrid Viability

A postzygotic barrier where genes of different parent species interact to impair the hybrid’s development or survival.

Reduced Hybrid Fertility

A postzygotic barrier where vigorous hybrids are sterile, often due to differences in parent species' chromosomes preventing normal gamete production.

Hybrid Breakdown

A postzygotic barrier where first-generation hybrids are viable and fertile, but offspring of subsequent generations are feeble or sterile.

Morphological Species Concept

A model that distinguishes a species by body shape and other structural features.

Ecological Species Concept

A model that defines a species in terms of its ecological niche, how its members interact with their environment.

Allopatric Speciation

Speciation that occurs when gene flow is interrupted as a population is divided into geographically isolated subpopulations.

Sympatric Speciation

Speciation that occurs in populations living in the same geographic area, often as a result of polyploidy.

Adaptive Radiation

The rapid emergence of several species from a common ancestor, often due to allopatric speciation in 'empty' environments.

Polyploidy

An accident during cell division that results in extra sets of chromosomes, often leading to new species in plants.

Autopolyploid

An individual with more than two chromosome sets, all derived from a single species (e.g., chromosome number doubles from 2N to 4N).

Allopolyploid

A fertile polyploid formed when two different species interbreed and produce hybrid offspring, which are usually sterile but can become fertile in subsequent generations.

Hybrid Zones

A region where members of different species meet, mate, and produce hybrid offspring.

Reinforcement (of Isolation Barriers)

An outcome in hybrid zones where prezygotic barriers are strengthened, reducing the formation of unfit hybrids until they gradually cease to be formed.

Fusion (of Isolation Barriers)

An outcome in hybrid zones where reproductive barriers are weak, leading to the two species fusing to form one species, reversing speciation.

Stability (of Hybrid Zone)

An outcome in hybrid zones where hybrids continue to be produced because they survive or reproduce better than members of either parent species, preventing species fusion.

Gradualism Evolution

A model of evolution where small changes accumulate over a very long period of time, leading to the creation of new species.

Punctuated Equilibrium

A model of evolution characterized by periods of apparent stasis punctuated by sudden, rapid bursts of change or speciation.