Study reproductive barriers, gene flow, and how populations can diverge into species.
Part of the free Knowledge Mountain biology library. Read an explanation, try a question, and use a memory cue to check what you can recall.
The biological species concept groups populations that can interbreed in nature and produce viable, fertile offspring, while being reproductively isolated from other such groups.
This concept has limits for fossils, asexual organisms, and some hybridizing groups. Different species concepts are useful for different questions.
Two frog species breed in different seasons. Is this a prezygotic or postzygotic barrier?
Prezygotic: temporal isolation.
The timing difference reduces the chance that a zygote forms. Postzygotic barriers act after fertilization, such as reduced hybrid survival or fertility.
Allopatric speciation begins with geographic separation that reduces gene flow. Mutation, selection, and drift can then make populations diverge until reproductive barriers evolve.
A mountain or river does not automatically create new species. The populations must become sufficiently reproductively isolated; geography provides an opportunity for divergence.
Can new species form without a geographic barrier? Give one mechanism.
Yes. For example, polyploidy can create reproductive isolation, especially in plants.
Sympatric speciation occurs in the same geographic area. Changes in chromosome sets, habitat use, or mating preferences can reduce gene flow.