Speciation and Species Concepts

These flashcards cover key vocabulary related to the concepts of speciation, species identification criteria, and mechanisms of isolation and divergence.

Speciation

The process of creating distinct species from an ancestral species, which can occur rapidly or gradually.

Genetic isolation

A barrier to gene flow that isolates two populations within species, leading to speciation.

Biological species concept

Defines species based on reproductive isolation, where distinct species do not interbreed or fail to produce viable, fertile offspring.

Morphospecies concept

Classifies species based on differences in size, shape, or other morphological traits.

Phylogenetic species concept

Defines a species as the smallest monophyletic group on the phylogenetic tree, based on evolutionary history.

Allopatric speciation

Speciation that occurs when populations are geographically isolated.

Sympatric speciation

Speciation that occurs in populations that live in the same geographic area but diverge genetically.

Premating isolating mechanisms

Barriers that prevent mating between species before fertilization, including habitat, temporal, and behavioral isolation.

Postzygotic isolating mechanisms

Barriers that occur after fertilization, affecting the viability or reproductive capacity of hybrid offspring.

Hybrid inviability

When hybrid offspring fail to develop or reach maturity.

Hybrid infertility

When hybrid offspring are sterile and cannot reproduce.

Hybrid breakdown

When hybrid offspring are viable and fertile, but subsequent generations are inviable or sterile.

Polyploidy

A condition in which an organism has more than two complete sets of chromosomes, often leading to speciation in plants.

Disruptive selection

A form of natural selection that favors extreme traits over intermediate ones, which can lead to sympatric speciation.

Ecological niche

The range of ecological resources and conditions needed by a species for survival and reproduction.

Reinforcement

Natural selection that favors traits preventing interbreeding between diverging populations when they come into contact.

Hybrid zone

A geographic area where interbreeding occurs between two distinct populations, producing hybrid offspring.

Gene flow

The transfer of genetic variation from one population to another, which can prevent speciation.