GRE Subject Test: Biology : Speciation

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #1 : Speciation

A certain class of protein is found to exist in several different species. The amino acid sequence of this protein is compared between a large number of species. The greatest number of amino acid differences will be found between species of different __________.

Possible Answers:

phyla

orders

families

genera

Correct answer:

phyla

Explanation:

The higher the taxonomic group, the less similar the members are. This is true for appearance, behavior, and genetics. The order of taxonomic groupings, from most general to most specific is: kingdom, phylum, class, order, family, genus, species.

Of the given answers, phyla are the highest taxonomic rank. Species of different phyla would show the greatest genetic difference. In contrast, genera are the lowest taxonomic rank of the given answers; species of the same genus would show the least genetic difference.

Example Question #2 : Speciation

Which of the following is an example of convergent evolution?

Possible Answers:

A species regains a trait that an ancestor had previously lost

Two different species independently gain the ability to fly

Two species merge together to form a single species

Two populations living in the same geographic region acquire enough differences to diverge into two separate species

Correct answer:

Two different species independently gain the ability to fly

Explanation:

Convergent evolution is the phenomenon by which two separate species evolve a shared trait. A classic example of this is that both birds and bats have evolved wings, but do not share a common ancestor prior to the development of this trait. Birds and bats developed their wings separately through completely unique mechanisms.

A population diverging into two separate species while residing in the same area describes the phenomenon of sympatric speciation. A species regaining a trait is an example of evolutionary reversal. 

Example Question #3 : Speciation

An example of __________ is the speciation of Darwin's finches through the accumulation of many small, distinct traits.

Possible Answers:

parsimony

divergent evolution

artificial selection

convergent evolution

Correct answer:

divergent evolution

Explanation:

Convergent evolution is the phenomenon by which two species independently evolve a similar trait. An excellent example is the evolution of flight/wings in birds and bats, which do not share a common ancestor. Parsimony is a principle that guides scientific explanation toward simple terms, rather than eleborate principles. By parsimonious thinking, the simplest explanation is also the most likely to be true. Artificial selection is a form of evolution in which organisms are selected and bred for beneficial traits that would not necessarily be selected for in nature. Dog breeding and the production of numerous types of produce and grains are subject to artificial selection by humans (this is different from genetic modification).

Divergent evolution describes the accumulation of distinct traits that can lead to speciation events. A large population consists of a single ancestor species. Over time, different groups of the population come to inhabit different niches and develop traits for specialized inhabitance of that niche. As these changes accumulate, the population slowly develops distinct groups. When these groups can no longer reproduce due to some sexual barrier, a speciation event has occurred. This process aligns with the theory of evolution for Darwin's finches.

Example Question #1 : Speciation

Which of the following refers to speciation that results from physical barriers such that biological populations become isolated?

Possible Answers:

Disruptive selection

Allopatric speciation

Natural selection

Sympatric speciation

Parapatric speciation

Correct answer:

Allopatric speciation

Explanation:

The correct answer is allopatric speciation. Sympatric speciation occurs when two biological populations inhabit the same geography, but speciate due to behavorial differences. Parapatric speciation occurs when there is a small hybrid zone or overlap of two biogeographically distinct populations. Disruptive selection and natural selection do not explain events of speciation in the context of the question. 

Example Question #5 : Speciation

Which of the following refers to speciation that occurs due to reproductive isolation in populations that occupy the same geographical area?

Possible Answers:

None of the other answers

Sympatric speciation 

Parapatric speciation 

Balancing selection

Allopatric speciation

Correct answer:

Sympatric speciation 

Explanation:

The correct answer is sympatric speciation. Although rare, sympatric speciation occurs in populations that occupy the same geography, but still develop reproductive isolation. This isolation is generally driven by behavioral differences. Allopatric speciation occurs in biogeographically distinct populations. Parapatric speciation occurs when there is a small hybrid zone or overlap of two biogeographically distinct populations. Balancing selection refers to a mode of natural selection, not speciation. 

Example Question #2 : Evolution

A scientist studies three populations of frog (populations A, B, and C) that live in the same rainforest. He notices some interesting similarities between the three groups. What would be the best evidence that A and B have a more recent common ancestor than A and C or B and C?

Possible Answers:

Populations A and B are both blue

Populations A and C often fight over territory

Populations A and B are not native to the rainforest, but came from two different areas that were very similar to the rainforest

Populations B and C eat different things

Populations A and B share similar mtDNA sequences, but differ in their nDNA sequences

Correct answer:

Populations A and B share similar mtDNA sequences, but differ in their nDNA sequences

Explanation:

Mitochondrial DNA (mtDNA) is only inherited directly from a mother to her offspring and can be used to directly track lineage of a population or species. Nuclear DNA (nDNA) is inherited from both the father and mother of the offspring; it can be used to track lineage as well, but mtDNA similarity is enough to conclude a close relationship between the two populations described in the question.

Color, diet, and location are all distinguishing features of the populations and help characterize their niche in the ecosystem. Diet and location (territory) are not heritable traits, and do not signify ancestry. Color is genetic, but could result from convergent or divergent evolution. mtDNA similarity is the strongest available evidence for a close ancestral link between populations A and B.

Example Question #7 : Speciation

Phylogenetics relates organisms to one another based on genetic distance that increases with evolutionary time. This principle requires the use of what kind of genes in order to give accurate relationships?

Possible Answers:

Genes under directional selection

Genes that are not under selection

Genes from the mitochondrial DNA

Genes from the nuclear DNA

Genes under sexual selection

Correct answer:

Genes that are not under selection

Explanation:

In order to derive an accurate estimate of phylogenetic relationships, scientists need to use neutral DNA markers in their studies. If genes are under any sort of selection, it could completely change the results, because this may not reflect the actual evolutionary past of the organisms. It is also generally important to incorporate both nuclear and mitochondrial DNA, because these types of genes can show different histories (remember, mitochondrial DNA is inherited maternally).

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