Species Concept and Speciation

Flashcards based on lecture notes about species concepts and speciation.

Species Fixity

The concept that each species remains unchanged since its creation.

Typological Species Concept / Morphological Species Concept

A species is a set of organisms that resemble one another and is distinct from other sets.

Ernst Mayr's definition of species

Groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.

Reproductively Isolated

Populations whose members do not mate with each other or who cannot produce fertile offspring.

Reproductive Isolating Mechanisms

Barriers to successful reproduction, including geographic, behavioral, mechanical, ecological, temporal, and gamete fusion barriers.

Prezygotic Isolating Mechanisms

Mechanisms that occur before the formation of a zygote, preventing mating or blocking fertilization.

Postzygotic Isolating Mechanisms

Reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown.

Reduced Hybrid Viability

Hybrid zygotes fail to develop or fail to reach maturity.

Reduced Hybrid Fertility

Even if hybrids are vigorous, they may be sterile.

Hybrid Breakdown

Offspring of hybrids have reduced viability or fertility.

Paleontological Species Concept

Focuses on morphologically discrete species known only from the fossil record.

Phylogenetic Species Concept

Defines a species as a set of organisms with a unique genetic history, as one branch on the tree of life.

Ecological Species Concept

Views a species in terms of its ecological niche, its role in a biological community.

Speciation

The process by which new species arise either by transformation of one species into another (anagenesis) or by the splitting of one ancestral species into two descendant species (cladogenesis).

Anagenesis

Transformation of one species into another.

Cladogenesis

Splitting of one ancestral species into two descendant species, leading to diversity.

Allopatric Speciation

Speciation that takes place in populations with geographically separate ranges.

Sympatric Speciation

Speciation that takes place in geographically overlapping populations.

Parapatric Speciation

Adjacent populations evolve into distinct species while maintaining contact along a common border.

Polyploidy

Greater than 2 sets of chromosomes

Autopolyploidy

Arises from genome duplication within a single species.

Allopolyploidy

Arises from hybridization plus genome duplication.

Homeologous pairing

Chromosomes from different species.