Exam 13: The Origin of Species

Which of the following is not true regarding the accumulation of genetic differences in allopatric populations?

Under the biological species concept,

Which of the following conditions is/are thought to be necessary for sympatric speciation to occur?

Shapiro's variation on the stable ecotype model is most analogous to which species concept?

You are studying a potential case of incipient sympatric speciation involving two morphs of a cichlid fish in a crater lake that feed at different depths and differ in morphology. If true, which of the following statements would make sympatric speciation more likely (or at least possible)? i. The two morphs specialize on different food types; matings between the morphs produce offspring that are intermediate and can efficiently utilize both food types. Ii) The two morphs feed on different food types, and there is strong disruptive selection operating such that individuals that are intermediate are very strongly selected against (basically none survive). Iii) Mating occurs in the area of the lake where each morph feeds. Also, females choose males based on jaw morphology, preferring males that have the same jaw morphology as the female. Iv) The two morphs feed at different depths, but both morphs come to a rocky area near the shore to mate. Females prefer to mate with males of the other morph.

You are studying 20 lake populations of the three-spined stickleback. In each lake, there are two distinct morphs that specialize on feeding in different areas of the lake. The benthic morph feeds around the shoreline, while the limnetic morph feeds in the open water. The environments and food sources in these environments are quite different. You hypothesize that these morphs are diverging into two different species in accordance with the ecological speciation model. Please describe an experiment that would allow you to test this hypothesis. Be sure to include what results would support and refute the ecological speciation hypothesis.

Which species concept(s) focus(es) focuses primarily on the reproductive isolation of populations?

Which of the following is not an example of horizontal gene transfer?

What evidence did Janzen and colleagues find while studying the neotropical skipper butterfly, Astraptes fulgerator, that led them to test whether it was a cryptic species. What are the implications of their findings?

Put the following stages of allopatric speciation in a terrestrial beetle population in the correct order. i. Mutation, drift, and selection act separately on the two subpopulations, and they become increasingly divergent. Ii) A river dries up, and the population has continuous geographic range with reproductive barriers that reduce gene flow between certain individuals. Iii) A river physically divides the population into two subpopulations. Iv) The population has continuous geographic range with some genetic variation.

How did the formation of the Isthmus of Panama influence the speciation of shrimp?

The biological, phylogenetic, and general lineage species concepts each have their strengths and weaknesses. Compare and contrast all three and evaluate them for their relative usefulness. Based on your answer, describe the recent speciation of polar bears and whether you think it is useful to call them a species separate from brown bears.

A river that divides a population of terrestrial salamanders could lead to

Which of the following is/are required to designate populations as separate species under the phylogenetic species concept?

The phylogenetic species concept may not be useful for microbial species because

Allopatric speciation is probably the most common way that new species form. Please describe a hypothetical scenario in which an initial ancestral population could split to form a new species through allopatric speciation. A fully correct answer will incorporate the following terms: gene flow, divergence, natural selection (including sexual selection), genetic drift, reproductive isolation, and reinforcement.

Please provide a real or hypothetical example of (a) pre-mating, (b) post-mating, prezygotic, (c) intrinsic postzygotic, and (d) extrinsic postzygotic reproductive isolating barriers.

Describe how some biologists have proposed to use adaptation as a criterion for identifying bacterial species. What is a potential drawback of this approach?

How do researchers make an initial determination about which microbes are different species using the phylogenetic species concept?

Early classifications of the polar bear were based on