AP Biology : Understanding Sympatric and Allopatric Speciation

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Understanding Sympatric And Allopatric Speciation

The wing structures of bats and birds are examples of which of the following?

Possible Answers:

Allopatric speciation

Convergent evolution

Divergent evolution

Genetic drift

Homology

Correct answer:

Convergent evolution

Explanation:

Bird wings and bat wings arose independently of one another, as they do not share a common ancestor with wings, therefore this is convergent evolution.

Divergent evolution implies a common ancestor from which different traits arise, so that is incorrect. It is not homology, as homology describes structures that are similar due to a common ancestry. Allopatric speciation is the emergence of new species due to a geographic barrier. Genetic drift is random variation in population genetic structure of a single species, which is unrelated to the topic at hand.

Example Question #1 : Understanding Sympatric And Allopatric Speciation

A physical barrier separates a single species, causing two separate populations to form. Over time these two populations adapt to their environments. Eventually, these two populations are no longer able to successfully reproduce with each other. This is known as __________.

Possible Answers:

parapatric speciation

peripatric speciation

allopatric speciation

sympatric speciation

Correct answer:

allopatric speciation

Explanation:

Allopatric speciation refers to the process by which a physical barrier separates a single population, causing two (or more) populations to arise and evolve due to environmental differences to become different species. Examples of factors that can lead to allopatric speciation include island formation, canyon and valley formation, and river paths.

Example Question #2 : Understanding Sympatric And Allopatric Speciation

Which scenario is an example of allopatric speciation?

Possible Answers:

Hawks with thin, sharp beaks primarily eat fish and small rodents, while hawks with larger beaks tend to eat reptiles and larger birds

Houseflies from a certain region migrate and interbreed with a different housefly population in a neighboring area

A river separates members of a squirrel population that used to occupy the same geographical area

Certain members of a human population have more offspring than others

A disease ravages a large fox population, killing all members that did not have a genetic resistance to the disease

Correct answer:

A river separates members of a squirrel population that used to occupy the same geographical area

Explanation:

Allopatric speciation occurs when a geographical barrier, like a river, mountain, or canyon, separates members of a population. This barrier prevents the individuals on one side from reproducing with the individuals on the other. In addition, selecting forces may act differently on the two sides of the barrier. This separation eventually results in two distinct species.

Here, the only example of allopatric speciation is that regarding the squirrels separated by the river. The example with the hawks refers to sympatric speciation, where no geographical barrier exists, but speciation can still occur due to other stressors. The remaining choices do not describe speciation at all.

Example Question #3 : Understanding Sympatric And Allopatric Speciation

Which of the following reasons could explain why sympatric speciation is more common in plants than in animals?

Possible Answers:

Plants are less prone to chromosomal abnormalities 

Plants are more likely to be able to self-fertilize 

Animal populations move around too much

Plants can become geographically isolated more easily

Correct answer:

Plants are more likely to be able to self-fertilize 

Explanation:

Sympatric speciation implies a speciation event while the populations exist within the same geographical region.

Animals moving around more often does not really explain why speciation would occur differently, and plants are not necessarily less prone to chromosomal abnormalities. In fact, plants are more likely to be able to reproduce after abnormal chromosomal inheritance (nondisjunction, polyploidy, etc.) because many can self-fertilize. Instead of wandering around to find a mate, the plant can reproduce with itself and potentially create a reproductively isolated species.

Example Question #1 : Understanding Sympatric And Allopatric Speciation

Which of the following would be considered an example of conditions leading to allopatric speciation?

Possible Answers:

Females selecting mates based on courtship displays

Separation of a population of lake fish by a drought resulting in a sand bar dividing the lake

Combat amongst males to show superiority for mating with females

A differentiation in preferred food source by members of a population within a given habitat

Correct answer:

Separation of a population of lake fish by a drought resulting in a sand bar dividing the lake

Explanation:

Allopatric speciation results in the formation of a new species based on geographic separation of a population from its parent population. Geographic separation greatly restricts gene flow and, as a result of the isolation, other reproductive barriers may arise from the parent/ancestral species. Once reproductive barriers emerge in the allopatric population the ability to interbreed with the parent population may be prevented or highly impaired, even if the two populations were to come back into contact.

The other answer choices are factors of sympatric speciation, in which a population can give rise to a new species without geographic isolation.

Example Question #4 : Understanding Sympatric And Allopatric Speciation

What is required for sympatric speciation to occur?

Possible Answers:

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

Emergence of a reproductive barrier

Continuous gene flow between populations

Geographic separation of a population

Correct answer:

Emergence of a reproductive barrier

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.

Example Question #5 : Understanding Sympatric And Allopatric Speciation

Which of these animals would be least likely to undergo allopatric speciation?

Possible Answers:

Bird

Snake

Raccoon

Prehistoric human

E. coli

Correct answer:

Bird

Explanation:

Allopatric speciation occurs when two groups of organisms are separated by a physical or geographic barrier. Common examples of these barriers include mountain ranges, oceans, and even large rivers. The isthmus of Panama is a prime example of a geographical barrier and it separates the Atlantic and Pacific oceans. 

Certain barriers are more easily traversed by some animals than others. For instance, an animal such as a cat is more likely to be corralled by a river than a horse or dog because the latter two are known to swim more often. But a river poses no threat of isolation to a bird. Because of their mode of locomotion birds are least likely to be hindered by a geographical barrier than a snake, raccoon, or even a prehistoric human (modern globalization almost entirely eliminates human's vulnerability to allopatric speciation).

Example Question #2 : Understanding Sympatric And Allopatric Speciation

One species of organisms living in the same valley begin to diverge from each other over time and eventually two distinct species emerge that no longer mate with members of the other group. What type of speciation is this?

Possible Answers:

Sympatric speciation

Allosteric speciation

Sympathetic speciation

Allopatric speciation

None of these - this is not an example of speciation

Correct answer:

Sympatric speciation

Explanation:

Sympatric speciation occurs when a species of organisms becomes two different species whilst inhabiting the same area. Geographic barriers do not play a role in their divergence from one another. Allopatric speciation occurs because of a geographical barrier such as a mountain range. Sympathetic is not an evolutionary term and allosteric refers to specific sites on molecules in molecular biology and biochemistry.

Example Question #3 : Understanding Sympatric And Allopatric Speciation

Which of the following best describes the initial speciation event in allopatric speciation?

Possible Answers:

Genetic polymorphism

Isolated niche population

Geographic isolation

Partially isolated population

Correct answer:

Geographic isolation

Explanation:

Allopatric speciation occurs when one population separates into two geographically isolated populations. The geographic isolation prevents gene transfer and reproduction, allowing for genetic divergence between the two populations.

Example Question #10 : Speciation

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

Possible Answers:

Allopatric

Sympatric

Peripatric

Parapatric

Correct answer:

Allopatric

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.

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