The Origin of Species

Corresponds with my notes :)

Biological Species Concept

defines a species as a group of populations whose members have the potential to produce viable, fertile offspring with each other, but not with the members of any other groups.

Morphological Species Concept

defines a species as a group that shares similar morphological structures.

Ecological Species Concept

defines a species as a group of organisms that shares an environmental niche.

Phylogenetic Species Concept

defines a species as a group with common evolutionary history.

Pre-zygotic barrier

things that prevent an egg cell from becoming fertilized.

Post-zygotic barrier

causes that allow an egg to be fertilized, but cause problems post-fertilization.

Hybrid inviability

when two organisms can create a zygote together, but the zygote is unable to survive development. The fertilized egg cannot go beyond the egg stage.

Hybrid breakdown

when two organisms can create a zygote, and that zygote makes it past development, but further generations of the hybrid have problems. The first hybrid organism is viable, but problems arise in its offspring.

Hybrid sterility

when two organism can successfully create offspring together, but the hybrid offspring is infertile. Examples of this would be horses and donkeys creating mules or lions and tigers creating ligers.

Temporal isolation

isolation based on time. The organisms are kept apart by the times that they are active. For example, spring flowers cannot reproduce with autumn flowers because they are not active at the same time.

Habitat isolation

When two organisms are in different habitats, they cannot create a fertilized egg cell. This is isolation via geography.

Behavioral isolation

when the mating behaviors of two organisms are too different for the two to mate with each other. This is common in birds, as many birds have complex mating behaviors.

Mechanical Isolation

when male and female reproductive anatomy are incompatible with each other, so there is no way for the two organisms to mate.

Gamete Isolation

when the gametes of two organisms are incompatible. The sperm cannot penetrate the egg cell, so creating a fertilized egg is impossible.

Allopatric Speciation

when one population is separated into two populations because they are in different places. Speciation occurs due to geographical separation (think habitat isolation!)

Sympatric Speciation

when one population splits into two, but they stay in the same habitat. This can happen for a few reasons. Think of all the non geographic forms of reproductive isolation.