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When gene flow between two populations ceases, the potential for _____ exists.

speciation; Reproductive isolation (the cessation of gene flow) is necessary for speciation

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species that lived side by side in parts of their ranges. However, recent books show them as eastern and western forms of a single species, the yellow-rumped warbler. Apparently, the myrtle warbler and Audubon's warbler _____.

successfully interbreed and produce fertile offspring

Imagine that part of a population of South American finches is blown by a storm onto an island far offshore and manages to survive and reproduce there for a period of 10,000 years. After that period, a climate change results in lower sea levels and the reconnection of the island with the mainland. Members of the formerly isolated island finch population can now interact freely with members of the original mainland population. Which of the following observations would, by itself, lead you to conclude unequivocally that the island finch population had evolved into a distinct species, according to the biological species concept?

Individuals from the different populations sometimes mate with each other, but all of the resulting eggs are sterile.

Which of the following conditions is necessary for speciation to occur?

reproductive isolation

At which point in the adaptation of a population is it clear that speciation has occurred?

Gene pool changes establish reproductive barriers between two populations.

Prezygotic barriers _____.

prevent fertilization of gametes from members of closely related species

Three species of frogs, Rana pipiens, Rana clamitans, and Rana sylvatica, all mate in the same ponds, but they pair off correctly because they have different calls. This is a specific example of a _____ barrier, called _____.

prezygotic ... behavioral isolation

Which of the following reproductive barriers actually prevents individuals of closely related species from copulating successfully?

mechanical isolation

Two species of water lilies in the same pond do not interbreed because one blooms at night and the other during the day. The reproductive barrier between them is an example of _____.

temporal isolation

Which of the following is an example of a postzygotic reproductive barrier?

Two fruit flies of different species produce sterile offspring.

There are two groups of pine trees that appear to be very similar phenotypically and genotypically. However, one releases pollen in January, when the female structures of that group are receptive, and one in March. What kind of reproductive barrier is this?

Temporal isolation

The phylogenetic species concept emphasizes _____.

Common ancestry

Lake Victoria, in Africa, is home to a group of related fishes known as cichlids. Many of these fishes are similar in appearance but have different feeding habits. What is the best method for scientists to determine conclusively whether the fish are members of a population that has a lot of variation or members of entirely different species?

Observe the fish in their natural environment for possible instances of interbreeding leading to several generations of fertile offspring.

In practice, how do scientists distinguish most species?

by using the morphological species concept

Which species concept defines a species as a set of organisms with a unique genetic history?

phylogenetic species concept

Sometimes two phenotypically different populations interbreed to a limited extent, so that it is difficult to determine whether they are clearly separate species. This is not a concern to scientists because this _____.

may indicate that the formation of a new species is in progress

Which of the following organisms is most likely to be subject to allopatric speciation?

pine trees in Alaska and pine trees on the island of Madagascar

According to the experiment of Diane Dodd, can adaptive divergence of allopatric fruit fly populations lead to reproductive isolation?

No. After several generations, the formation of a reproductive barrier (behavioral isolation) was evident, but not absolute.

Which of the following evolutionary mechanisms does NOT contribute to the process of allopatric speciation?

Gene flow

In which of the following groups has sympatric speciation been most important?

Plants

If a new species of plant is to be produced by means of allopolyploidy from two parental species that are 2n = 4 and 2n = 8, how many chromosomes would you expect in the somatic cells of the new species?

12; The two gametes would be n = 2 and n = 4. They would combine for a total of 6, which after doubling would be 12.

A new species can arise in a single generation _____.

if a change in chromosome number creates a reproductive barrier

The Galápagos finches collected by Darwin are thought to have descended from a very small parent population. Different species of finches that are confined to only one or two islands most likely arose by _____.

Allopatric Speciation

In the case of the Lake Victoria cichlids, sympatric speciation has been shown to be driven by _____.

Sexual selection

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