Origin of species

Speciation

The evolutionary process by which populations evolve to become distinct species.

Biological Species Concept

Defines a species as a group of populations that can interbreed in nature and produce viable and fertile offspring.

Reproductive Isolation

Biological barriers that prevent interbreeding and successful production of offspring between different species.

Prezygotic Barriers

Barriers that hinder fertilization from occurring before the zygote is formed.

Postzygotic Barriers

Barriers affecting the viability or fertility of hybrids after fertilization has occurred.

Habitat Isolation

Populations live in different habitats, preventing them from interbreeding.

Behavioral Isolation

Unique courtship behaviors attract mates within a species but not others, preventing interbreeding.

Temporal Isolation

Species breed at different times, preventing interbreeding.

Mechanical Isolation

Anatomical incompatibility that prevents successful mating.

Gametic Isolation

Incompatibilities at the gamete level that prevent fertilization.

Reduced Hybrid Viability

Genetic incompatibility that may lead to aborted development of hybrids.

Reduced Hybrid Fertility

Hybrids that are vigorous but sterile, preventing reproduction.

Hybrid Breakdown

First-generation hybrids are viable and fertile, but subsequent generations are feeble or sterile.

Ecological Species Concept

Defines species by their ecological niche and interactions with the environment.

Phylogenetic Species Concept

Uses shared ancestry and evolutionary histories to define a species.

Allopatric Speciation

Speciation that occurs when geographic barriers lead to reproductive isolation.

Sympatric Speciation

Speciation occurring without geographic isolation, often through mechanisms like polyploidy or sexual selection.

Gradualism

The idea that evolution happens slowly and steadily over time.

Punctuated Equilibrium

A model proposing that species experience long periods of stasis interrupted by brief, rapid changes.

Divergent Evolution

New species evolve in response to varying environments after being geographically isolated.

Convergent Evolution

Different species develop similar characteristics due to adaptation to similar environments.

Parallel Evolution

Related species evolve similarly after diverging from a common ancestor.

Coevolution

Interdependent evolution of two species that influence each other’s adaptations.