Week 6

Which conclusion can be drawn from this evolutionary tree?

A single clade (that is, a group of species that share a common ancestor) can include species that formed by gradualism and other species that formed by punctuated equilibrium.

Which habitats should harbor snapping shrimp species with the greatest degree of genetic divergence from each other?

A5 and B5

What is the best way to promote fusion between two related populations of mosquitofish, one of which lives in a predator-rich pond and the other of which lives in a predator-poor pond?

Build a canal linking the two ponds that permits free movement of mosquitofish, but not of predators.

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 are rarely successful in producing offspring. What can you infer from this information?

Postzygotic isolation exists between the two frog species.

Why should deepwater shrimp on different sides of the isthmus have diverged from each other earlier than shallow-water shrimp?

They have been geographically isolated from each other for a longer time.

Dogs (Canis lupus familiaris) and gray wolves (Canis lupus) can interbreed to produce viable, fertile offspring. These species shared a common ancestor recently (in geologic time) and have a high degree of genetic similarity, although their anatomies vary widely. Judging from this evidence, which two species concepts are most likely to place dogs and wolves together into a single species? a. biological and phylogenetic b. biological and morphological c. ecological and morphological d. ecological and phylogenetic

a

In a hypothetical situation, a certain species of flea feeds only on pronghorn antelopes. In the western United States, pronghorns and cattle often associate with one another in the same open rangeland. Some of these fleas develop a strong preference for cattle blood and mate only with other fleas that prefer cattle blood. The host mammal can be considered as the fleas' habitat. If this situation persists, and new species evolve, this would be an example of _____. a. sympatric speciation and habitat isolation b. allopatric speciation and gametic isolation c. sympatric speciation and temporal isolation d. allopatric speciation and habitat isolation

a

Use the following description to answer the question(s) below. In the ocean, on either side of the Isthmus of Panama, are thirty species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are fifteen species on the Pacific side and fifteen different species on the Atlantic side. The Isthmus of Panama started rising about ten million years ago. The oceans were completely separated by the isthmus about three million years ago. In the following figure, 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. The Panama Canal was completed in 1914, and its depth is about fifty feet. After 1914, snapping shrimp species from which habitats should be most likely to form hybrids as the result of the canal? a. A1 and B1 b. A3 and B3 c. A5 and B5 d. A1-A3 and B1-B3 have equal likelihoods of harboring snapping shrimp species that can hybridize.

a

Use the following description to answer the question(s) below. In the ocean, on either side of the Isthmus of Panama, are thirty species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are fifteen species on the Pacific side and fifteen different species on the Atlantic side. The Isthmus of Panama started rising about ten million years ago. The oceans were completely separated by the isthmus about three million years ago. In the following figure, 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. Which habitats should harbor snapping shrimp species with the greatest degree of genetic divergence from each other? a. A5 and B5 b. A1 and A5 c. A1 and B5 d. Both A1/A5 and B1/B5 should have the greatest, but equal amounts of, genetic divergence.

a

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. If the two forms were unable to interbreed when their expanding ranges met, it would be an example of _____.

allopatric speciation

A hybrid zone is properly defined as _____. a. an area where members of two closely related species intermingle, but gene flow is prevented by prezygotic barriers b. an area where mating occurs between members of two closely related species, producing viable offspring c. a zone where sterile hybrids form, kept separate by postzygotic barriers d. an area where the ranges of two closely related species overlap, but do not interbreed

b

Which of the following describes the most likely order of events in allopatric speciation? a. genetic drift, genetic isolation, divergence b. genetic isolation, genetic drift, divergence c. divergence, genetic drift, genetic isolation d. genetic isolation, divergence, genetic drift

b

Dogs (Canis lupus familiaris) and gray wolves (Canis lupus) can interbreed to produce viable, fertile offspring. These species shared a common ancestor recently (in geologic time) and have a high degree of genetic similarity, although their anatomies vary widely. Judging from this evidence, which two species concepts are most likely to place dogs and wolves together into a single species?

biological and phylogenetic

Male frogs give calls that attract female frogs to approach and mate. Researchers examined mating calls of closely related tree frogs in South America. If reinforcement is occurring, what would you expect if you compare the calls of the two species in zones of sympatry versus zones of allopatry? a. Calls would be about the same in both areas. b. Calls would be more similar in areas of sympatry. c. Calls would be more different in areas of sympatry.

c

Use the following information to answer the question(s) below. About 3 million years ago, the Isthmus of Panama (a narrow strip of land connecting North and South America) formed, dividing marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sides of the isthmus. Based on the morphological species concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus, were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. (N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629-32.) Refer to the paragraph about the formation of the Isthmus of Panama. If the isthmus formed gradually rather than suddenly, what pattern of genetic divergence would you expect to find in these species pairs? a. similar percentages of difference in DNA sequence between all pairs of sister species b. greater percentage of difference in DNA sequence between species that inhabit shallow water than between species that inhabit deep water c. greater percentage of difference in DNA sequence between species that inhabit deep water than between species that inhabit shallow water

c

Use the following information to answer the question(s) below. About 3 million years ago, the Isthmus of Panama (a narrow strip of land connecting North and South America) formed, dividing marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sides of the isthmus. Based on the morphological species concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus, were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. (N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629-32.) Refer to the paragraph about the formation of the Isthmus of Panama. The sister populations on opposite sides of the isthmus are true species under which species concept? a. the phylogenetic species concept b. the morphological species concept c. the morpholoogical species, biological species, and phylogenetic species concepts d. the biological species concept

c

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 are rarely successful in producing offspring. What can you infer from this information? a. Prezygotic isolation exists between the two frog species. b. The hybrids form a separate species under the biological species concept. c. These two species are likely in the process of fusing back into one species. d. Postzygotic isolation exists between the two frog species.

d

Refer to the paragraph about the formation of the Isthmus of Panama. If the isthmus formed gradually rather than suddenly, what pattern of genetic divergence would you expect to find in these species pairs?

greater percentage of difference in DNA sequence between species that inhabit deep water than between species that inhabit shallow water

According to the concept of punctuated equilibrium, the "sudden" appearance of a new species in the fossil record means that _____.

speciation occurred rapidly in geologic time

Refer to the paragraph about the formation of the Isthmus of Panama. The sister populations on opposite sides of the isthmus are true species under which species concept?

the morpholoogical species, biological species, and phylogenetic species concepts