Chapter 24 Biology

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

gene flow

Two animals are considered members of different species if they _____.

cannot mate and produce viable, fertile offspring

According to the phylogenetic species concept, what is a species?

a set of organisms with a unique genetic history

Which of these is an example of temporal isolation?

one species is nocturnal, and the other is not

Which of the following is the first step in allopatric speciation?

geographic isolation

Sympatric speciation is _____.

the appearance of a new species in the same area as the parent population

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

autopolyploidy

Hybrid zones provide an opportunity to investigate _____.

the evolution of reproductive isolation

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

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

punctuated equilibrium

The largest unit within which gene flow can readily occur is a

species

Males of different species of the fruit fly Drosophila that live in the same parts of the Hawaiian Islands have different elaborate courtship rituals. These rituals involve fighting other males and making stylized movements that attract females. What type of reproductive isolation does this represent?

behavioral isolation

According to the punctuated equilibria model,

most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.

Bird guides once listed the myrtle warbler and Audubon’s warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?

The two forms interbreed often in nature, and their offspring have good survival and reproduction.

Which of the following factors would not contribute to allopatric speciation?

gene flow between the two populations is extensive

Plant species A has a diploid number of 12. Plant species B has a diploid number of 16. A new species, C, arises as an allopolyploid from A and B. The diploid number for species C would probably be

28

Suppose that a group of male pied flycatchers migrated from a region where there were no collared flycatchers to a region where both species were present (see Figure 24.15 in your textbook). Assuming events like this are very rare, which of the following scenarios is least likely?

the frequency of hybrid offspring would decrease

How long does it take new species to form on Earth?

the time required varies considerably

Select the correct statement describing sympatric speciation.

sympatric speciation can occur in a single generation

Adaptive radiations on archipelagos (island chains) represent some of the best-understood speciation events. Why is an ancestral species more likely to give rise to multiple descendent species on an archipelago than on an equal-sized area of mainland?

Populations on nearby islands are more likely to be genetically isolated than populations that are equally close to one another on the mainland.

The original habitat of the North American maggot fly, Rhagoletis pomonella, was native hawthorn trees. About 200 years ago, some populations colonized newly introduced apple trees. The two populations are still classified as subspecies, but sympatric speciation is under way. What has contributed to incipient speciation in the maggot fly?

Because apples mature more quickly than hawthorn fruit, the apple-feeding flies have been selected for more rapid development.