High School Biology : Understanding Speciation

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understanding Speciation

Which of the following would be LEAST likely to lead to speciation?

Possible Answers:

A volcanic eruption creates a barrier separating two populations of rodents.

A single coconut is carried to a remote island in the Pacific Ocean by water currents. 

A flock of sparrows is blown off course to an island far from their natural habitat.

A mutation arises within a population of orchids that prevents the orchids from breeding with other populations of orchids.

Correct answer:

A single coconut is carried to a remote island in the Pacific Ocean by water currents. 

Explanation:

Speciation usually relies on the isolation (either geographical or reproductive) of a group of individuals. The coconut example would be unlikely to lead to speciation due to the fact that that it is only one coconut. If many coconuts arrived, then it would be much more likely.

Example Question #2 : Understanding Speciation

Which of the following is not a type of speciation?

Possible Answers:

Allopatric

Orthopatric

Sympatric

Peripatric

Correct answer:

Orthopatric

Explanation:

Allopatric speciation occurs when organisms become separated by a geographical barrier. Over time, distinct species develop due to the separation of the original population.

Sympatric speciation occurs when organisms evolve into distinct species over time in a single location due to specialization and natural selection.

Peripatric speciation is a type of allopatric speciation in which a small part of a population is separated from the main population and evolves in isolation. The founder effect is often observable in the separated population.

Orthopatric is not a type of speciation, so it is the correct answer.

Example Question #17 : Genetics And Evolution

As a result of rising ocean levels, an island that once contained a homogenized population of arabidopsis has now undergone genetic drift. The island has been divided into two parts, separated by a significantly large body of water. What is likely to have happened to result in two genetically different populations that can no longer reproduce?

Possible Answers:

Sex linked genes 

Synetny

Adaptive radiation

Artificial selection

Allopatric speciation

Correct answer:

Allopatric speciation

Explanation:

Speciation involves events causing the creation of a new species. Therefore, the separation of the two groups of arabidopsis caused an allopatric speciation event to occur given that the two populations could no longer cross breed. Adaptive radiation involves the rapid diversification of characteristics of a species, which may lead to speciation over time. Artificial speciation involves humans directly influencing allele frequencies. For example, deliberately continuously crossing the largest pigs in a farm to increase the average weight of the pigs. 

Example Question #2 : Understanding Speciation

A species of fruit fly that traditionally inhabits the western slope of a mountain was blown by the wind to reach the eastern side of the mountain. Over time, the fruit fly population on the eastern side of the mountain lost its ability to mate with the western fruit flies when they encountered each other. This is an example of which type of speciation?

Possible Answers:

Sympatric speciation

Hypopatric speciation

Parapatric speciation

Allopatric speciation

Correct answer:

Allopatric speciation

Explanation:

Allopatric speciation takes place when a group of individuals becomes physically isolated from the original population and starts to evolve separately. When individuals from the two populations stop mating regularly gene flow is reduced and over time the populations will start to lose the ability to recognize each other and successfully mate. This phenomenon leads to the speciation of one species into two.

Example Question #19 : Genetics And Evolution

A certain type of flower used to grow on both sides of the Amazon River. However, over time, the salinity of the soil on the north side grew significantly, while the salinity on the south side stayed the same. Over time, the flowers on one side became unable to reproduce with the flowers growing along the opposite bank because their offspring could not survive in the saline conditions; however, these plants were formerly of the same species. 

What type of speciation is described?

Possible Answers:

Sympatric speciation

Artificial speciation

Peripatric speciation

Allopatric speciation

Parapatric speciation

Correct answer:

Parapatric speciation

Explanation:

Parapatric speciation is a type of speciation that occurs when an extreme change in habitat occurs and separates a species from members of its groups. This does not have to do with geographic barriers, but a difference in climates or conditions. In this case, the salinity of the soil on one side separated the flowers from mating with their own species, thus delineating them.

Allopatric speciation is a separation of species due to geographic location. For example, the speciation of Darwin's finches is allopatric speciation—the finches eventually lost the ability to interbreed due to being on separate islands. 

Sympatric speciation is when a species is still in the same geographic location, but becomes reproductively isolated. This usually happens through a mutation during reproduction when the offspring recieves twice the number of normal chromosomes. This individual possesses a quality called tetraploidy, and cannot reproduce with other diploids. 

Peripatric is similar to allopatric speciation in that the individuals are separated by geographic barriers. However, the main difference is that the group that is broken off is much smaller and may possess a certain quality or trait that, due to the small group, is made a more predominant quality or trait.

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