Speciation

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AP Biology › Speciation

Questions 1 - 10
1

Which of the following is false of sympatric populations?

Sympatric populations diverge due to geographic isolation

Sympatric populations are geographically overlapping

Sympatric populations diverge due to behavioral isolation

Sympatric populations show differences in body structure

Sympatric populations may form hybrids

Explanation

Allopatric literally means “other fatherland,” meaning that populations are geographically separate. Because populations are separate, they may use similar resources and be similar in structure. Allopatric populations come about due to geographic isolation, rather than behavioral isolation. Sympatric means “same fatherland,” meaning that populations are geographically overlapping and diverge due to behavioral isolation. As a result, they may also, show divergence from a common resource and original body structure. Where the two sympatric populations overlap, there is a hybrid zone. The two species may mate and produce hybrid offspring.

2

Which of the following best defines sympatric speciation?

Formation of two distinct species within the same geographic location

Populations diverge due to geographic location

Isolated peripheral populations cease genetic exchange

A population divides into two adjacent niches with contact and minimal genetic exchange

Explanation

In cases of sympatric speciation, two distinct species diverge from the same population within the same geographic location.

3

Peripatric speciation is a subgroup of which of the following types of speciation?

Allopatric

Sympatric

Parapatric

Peripatric

Explanation

Peripatric speciation is a subgroup of allopatric speciation. In instances of peripatric speciation, a small portion of the population becomes genetically isolated from the main population; therefore, it becomes genetically distinct. An example of peripatric speciation is the founder effect.

4

Peripatric speciation is a subgroup of which of the following types of speciation?

Allopatric

Sympatric

Parapatric

Peripatric

Explanation

Peripatric speciation is a subgroup of allopatric speciation. In instances of peripatric speciation, a small portion of the population becomes genetically isolated from the main population; therefore, it becomes genetically distinct. An example of peripatric speciation is the founder effect.

5

What is required for sympatric speciation to occur?

Emergence of a reproductive barrier

Geographic separation of a population

Continuous gene flow between populations

A limited separation of members of a population, followed by reintroduction back into the parent population

Explanation

Sympatric speciation refers to the evolution of a new species from a parent population without geographic isolation. The divergence into a new species requires the formation of a reproductive barrier that isolates a subset of the population from the rest, thereby blocking gene flow.

The formation of a reproductive barrier can result from polyploidy or natural selection. If a subset of a population chooses to only eat fruit that have fallen from trees while the rest climb the trees to eat, then the subset may eventually evolve different traits. Polyploidy creates a distinct genetic difference between individuals and can lead to difference phenotypes and reproductive barriers.

6

Which of the following is false of sympatric populations?

Sympatric populations diverge due to geographic isolation

Sympatric populations are geographically overlapping

Sympatric populations diverge due to behavioral isolation

Sympatric populations show differences in body structure

Sympatric populations may form hybrids

Explanation

Allopatric literally means “other fatherland,” meaning that populations are geographically separate. Because populations are separate, they may use similar resources and be similar in structure. Allopatric populations come about due to geographic isolation, rather than behavioral isolation. Sympatric means “same fatherland,” meaning that populations are geographically overlapping and diverge due to behavioral isolation. As a result, they may also, show divergence from a common resource and original body structure. Where the two sympatric populations overlap, there is a hybrid zone. The two species may mate and produce hybrid offspring.

7

Which of the following best defines sympatric speciation?

Formation of two distinct species within the same geographic location

Populations diverge due to geographic location

Isolated peripheral populations cease genetic exchange

A population divides into two adjacent niches with contact and minimal genetic exchange

Explanation

In cases of sympatric speciation, two distinct species diverge from the same population within the same geographic location.

8

What is required for sympatric speciation to occur?

Emergence of a reproductive barrier

Geographic separation of a population

Continuous gene flow between populations

A limited separation of members of a population, followed by reintroduction back into the parent population

Explanation

Sympatric speciation refers to the evolution of a new species from a parent population without geographic isolation. The divergence into a new species requires the formation of a reproductive barrier that isolates a subset of the population from the rest, thereby blocking gene flow.

The formation of a reproductive barrier can result from polyploidy or natural selection. If a subset of a population chooses to only eat fruit that have fallen from trees while the rest climb the trees to eat, then the subset may eventually evolve different traits. Polyploidy creates a distinct genetic difference between individuals and can lead to difference phenotypes and reproductive barriers.

9

A researcher has discovered two species of frogs that live in the same location. In the lab he is able to generate a viable hybrid by combining gametes from each species, however, no such hybrids exist in the wild. Which of the following methods of reproductive isolation might explain this phenomenon?

Temporal isolation

Habitat isolation

Gametic isolation

Hybrid breakdown

Explanation

Out of the choices, only temporal isolation can explain this phenomenon. Temporal isolation describes a type of reproductive isolation that comes about because the two species mate at different times.

Habitat isolation cannot explain this occurrence because we are told that the two species live in the same area. Hybrid breakdown also cannot be correct because the researcher was able to generate a viable hybrid (so he should reasonably be able to find first generation hybrids in the wild). Gametic isolation is also not correct because a hybrid was successfully generated.

10

Which is not an example of behavioral isolation?

Species of fish living in different areas of a pond due to differential salt concentrations

Two species of bird having distinct male mating dances

Pheremones that attract only one species of insect

Male plumage on a bird species that is only found to be attractive by females of the same species

Explanation

Behavioral isolation is a type of pre-zygotic barrier to reproduction that isolates species through different mating rituals. “Species of fish living in different areas of a pond due to differential salt concentrations” is not an example of behavioral isolation because there is not difference in mating behaviors that reproductively isolates the two species of fish. The rest of these examples demonstrate barriers to reproduction that originate with mating behavior.

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