Chapter 17

Lineage Species Concept

A species is a single lineage of ancestor-descendant populations which maintain its identity from other such lineages and which has it own evolutionary tendencies and historical fate

Gametic Isolation

A type of prezygotic barrier. Gametic isolation happens when the egg and sperm are released but a zygote is not formed. Reproductive cells are not compatible

Postzygotic Isolating Mechanisms

A type of reproductive isolating mechanism which comes into play after the gametes of two different species have fused to create a hybrid zygote. These mechanisms may prevent the proper development of the hybrid and/or make it infertile, thus the hybrid is unable to successfully reproduce.

Cryptic Species

Cryptic speciation is a biological process that results in a group of species (which, by definition, cannot interbreed) that contain individuals that are morpholigically identical to each other but belong to different species.

Prezygotic Isolating Mechanisms

Reproductive isolating mechanisms which prevent the formation of a zygote between members of different species. These mechanisms include geographical isolation, ecological isolation, temporal isolation, behavioral isolation, mechanical isolation, and gametic isolation.

Sympatric Speciation

Speciation due to reproductive isolation without any physical separation of the subpopulation.

Allopatric Speciation

The formation of two species from one when reproductive isolation occurs because of a physical geographic barrier.

Speciation

The process of splitting one population into two populations that are reproductively isolated from one another.

Reproductive Isolation

When isolating mechanisms make it so two species can not reproduce.

Biological Species Concept

Where one species is reproductively isolated from another species, meaning they cannot breed and reproduce with species other than their own.

Temporal Isolation

A form of prezygotic isolation that prevents species from mating because they mate at different times.

Mechanical Isolation

A form of prezygotic isolation where the size and shape of an organisms genitalia can only fit into that of its own species.

Morphological Species Concept

Organisms are classified in the same species if they appear identical

Polyploidy

Polyploid cells and organisms are those containing more than two paired (homologous) sets of chromosomes.

Behavior Isolation

Prezygotic isolation usually in the form of mating rituals and signals. Signals that attract mates to each other may be one of the most important factors in determining whether closely related species mate with each other or not.

Habitat (Ecological) Isolation

Prezygotic isolation where species may live in the same place but different habitats. For example one lives underground while the other lives in a tree

Reinforcement

Reinforcement is the process by which natural selection increases reproductive isolation.

Hybrid Breakdown

hybrid produces offspring but offspring not viable or fertile

Punctuated Equilibrium

long periods of stasis punctuated by episodes of speciation. species develop in spurts of rapid NOT slow & gradual change

Low Hybrid Fertility

the hybrid is sterile

Low Hybrid Viability

zygote fails to develop or reach sexual maturity