Evolutionary Biology: Species Concepts and Reproductive Isolation

Flashcards covering species concepts, reproductive isolation mechanisms, and different modes of speciation (allopatric and sympatric), along with illustrative examples from evolutionary biology.

Morphological Species Concept

Individuals of a single species share measurable traits.

Carolus Linnaeus

Scientist associated with the Morphological Species Concept.

Biological Species Concept (BSC)

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

Ernst Mayr

Scientist associated with the Biological Species Concept.

Reproductively Isolated

A characteristic of different species where members do not mate or cannot produce fertile offspring.

Reproductive Isolating Mechanisms

Mechanisms that prevent species from interbreeding successfully.

Prezygotic Isolating Mechanisms

Mechanisms that prevent the formation of a hybrid zygote.

Postzygotic Isolating Mechanisms

Mechanisms that act after a zygote has formed to prevent viable or fertile offspring.

Habitat Isolation

A prezygotic mechanism where species occur in different areas (geographically or ecologically) and rarely encounter each other.

Temporal Isolation

A prezygotic mechanism where species breed at different times.

Behavioral Isolation

A prezygotic mechanism where species have different courtship rituals or behaviors that prevent mating.

Mechanical Isolation

A prezygotic mechanism where physical differences prevent the transfer of gametes between species.

Gametic Isolation

A prezygotic mechanism where gametes fail to unite successfully.

Allopatric

Occurring in separate, non-overlapping geographical areas.

Sympatric

Occupying the same or overlapping geographical areas.

Hybrid Inviability

A postzygotic mechanism where hybrid offspring does not survive.

Hybrid Infertility

A postzygotic mechanism where hybrid offspring are infertile.

Hybrid Breakdown

A postzygotic mechanism leading to infertility in later hybrid generations.

Speciation

The process by which one species becomes two, typically through reproductive isolation.

Allopatric Speciation

The process where one species becomes two due to geographic isolation.

Dispersal Isolation

A type of allopatric speciation achieved when a small group starts a new population in a separate area.

Vicariance Isolation

A type of allopatric speciation where a geographical barrier emerges that splits a population into two.

"Missing Link" Isolation

A term for a type of isolation that leads to species formation when a population becomes isolated by disappearing intermediate populations.

Gene Flow

The transfer of genetic material from one population to another; acts to counter isolation in speciation.

Sympatric Speciation

Speciation occurring in the same geographical area without physical separation.

Polyploidy

A mechanism for sympatric speciation where an organism has more than two sets of chromosomes.

Disruptive Selection

A type of natural selection where extreme phenotypes are favored over intermediate ones, which can lead to sympatric speciation.

Adaptive Radiation

The rapid diversification of a single ancestral species into many new species, often occurring when a species enters a new area with many under-utilized resources.

Subspecies

Populations within a species that typically interbreed at the borders of their ranges but have distinct characteristics.

Ring Species

A series of populations arranged geographically in a ring, where adjacent populations can interbreed, but the two end populations cannot.

Liger

A hybrid offspring resulting from a male lion and female tiger, often infertile due to hybrid infertility.

Mule

A hybrid offspring resulting from a male donkey and female horse, infertile and an example of hybrid infertility.

Cycad

An example of a plant group whose distribution has been affected by vicariance due to continental drift.

Pea aphid

An example where early stages of sympatric speciation have been observed through host plant specialization.

Silverswords

A group of plants in Hawaii thought to have descended from a single immigrant species, demonstrating adaptive radiation.

Salamanders (Ensatina)

A classic example of a ring species in western North America.