Chapter 24 Questions
- In your own words, define species. Why is it such a difficult term to define? (4 points)
- You are confronted with a box of preserved grasshoppers of various species that are new to science and have not been described. Your assignment is to separate them into species. There is no accompanying information as to where or when they were collected. (7 points total)
- What species concept would you use to separate out the species? Why? (2 points)
- If you were able to collect DNA from these grasshoppers, would the information from the DNA be helpful in determining whether two organisms were from the same species? Why/why not? What would you want to find out? (3 points)
- If you found out later that one group of these grasshoppers was found in the rain forests of Asia, while another group was found in the deserts of Australia, would you consider the two groups to be different species? Why? What species concept(s) would you use? (2 points)
- House finches were found only in western North America until 1939, when a few individuals were released in New York City. These individuals established a breeding population and gradually expanded their range. The western population also expanded its range somewhat eastward, and the two populations have recently come in contact. When their expanding ranges met, the two forms were unable to interbreed (no hybrids were found), even though they tried to mate. (6 points total)
- Did speciation occur here? If so, was it due to allopatric or sympatric speciation? Explain. (2 points)
- What species concept(s) could apply here? Explain. (2 points)
- Based on the information above, what specific reproductive barrier must have been established? Why? (2 points)
- Two researchers experimentally formed tetraploid (4n) frogs by fertilizing diploid eggs from Rana porosa brevipoda (2n=26) with diploid sperm from Rana nigromaculata (2n=26). When they mated these tetraploid frogs with each other, most of the offspring that survived to maturity were tetraploid, with chromosome sets of both diploid parent species. (8 points total)
- What kind of polyploidy do the hybrids have? How many unreplicated chromosomes are in a typical cell in the hybrid? (3 points)
- Based on these results, if this type of tetraploid formed in the wild, would they be able to mate with either of the parent species? Why/why not? (3 points)
- Is this a type of speciation allopatric or sympatric? Why? Why wouldn’t it be the other kind? (2 point)
- The common edible frog of Europe is a hybrid between two species, Rana lessonae and Rana ridibunda. The hybrids were first described in 1758 and have a wide distribution, from France across central Europe to Russia. Both male and female hybrids exist, but when they mate among themselves, they do not produce offspring. (5 points total)
- What kind of reproductive barrier is seen here? Explain. (2 points)
- If after some time, the hybrids were able to mate among themselves and with those of their parent species, is reinforcement, fusion, or stabilization occurring here? What is happening to reproductive barriers? How could these reproductive barriers have been changed? What do you think will eventually happen to the two different species? Explain. (3 points)
- In the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. Over the next 7 million years, the isthmus rose until the oceans were completely separated by the isthmus about 3 million years ago.
In the figure below, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1-5), with 1 being the shallowest.
- Is the evolution of the 30 shrimp species from the 15 original species an example of allopatric or sympatric speciation? Why? Would deepwater shrimp on different sides of the isthmus have diverged from each other earlier than shallow-water shrimp? Why? (3 point)
- Does the speciation of these sister species provide an example of the gradual model or the punctuated equilibrium model of speciation? Explain. (2 points)
