What is the most important factor that holds a gene pool of a species together and prevents speciation?
Gene flow

– Gene flow refers to the transfer of alleles among populations. As long as populations are exchanging alleles, speciation is unlikely.

Two animals are considered members of different species if they _____.
cannot mate and produce viable, fertile offspring.

– If two individuals cannot interbreed and produce viable, fertile offspring, they are members of different species.

According to the phylogenetic species concept, what is a species?
a set of organisms with a unique genetic history
Which of the following is the first step in allopatric speciation?
geographic isololation

– Allopatric speciation occurs when a population of organisms is geographically separated long enough for significant changes to occur. After a period of time, the populations may no longer be able to interbreed.

Which of these is an example of temporal isolation?
One species is nocturnal, and the other species is not.

– In temporal isolation, two species that breed during different times of the day cannot mix their gametes.

Sympatric speciation is _____.
the appearance of a new species in the same area as the parent population

– It is due to a radical change in the genome.

Hybrid zones provide an opportunity to investigate _____.
the evolution of reproductive isolation

– A hybrid zone allows researchers to see what happens when closely related species come together. Reproductive barriers may be strengthened or weakened, depending on environmental and genetic factors.

A certain species of salamander was split into two populations by a wide, dry valley, and the populations began to diverge from each other. After a period of time, some members of the two populations began to interbreed in a hybrid zone at the southern end of the valley. Only weak reproductive barriers existed by this time, so the two populations could freely interbreed and re-establish gene flow. This outcome in a hybrid zone is known as _____.
– fusion

Fusion refers to the weakening of reproductive barriers, allowing the two populations to fuse and remain (or become) one species.

According to the _____ model, evolution occurs in spurts; species evolve relatively rapidly then remain unchanged for long periods.
punctuated equilibrium

– This is the definition of punctuated equilibrium.

Which of the following has been shown to cause speciation most rapidly?
autopolyploidy

– Autopolyploidy has been shown to produce nearly instantaneous speciation in plants.

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