evolution unit test study guide

Which of the following statements best explains the change in herbicide-resistant horseweed populations over time?

• Individual horseweed plants that are resistant to the herbicide increased over time by surviving and reproducing, and passing their herbicide-resistant genes to their offspring.

• Horseweed plant populations resistant to the herbicide increased over time by growing in areas where the herbicide is not present, increasing their chance of survival.

• Numbers of individual horseweed plants remained the same over time, however they reproduced at different rates. Since the herbicide-resistant individuals can reproduce faster and increase their genes in the population, the population became more resistant over time.

• Numbers of individual horseweed plants remained the same over time, however they developed genes that make them more resistant to herbicides. As the resistant individuals pass their genes on to other populations, the horseweed plants become more resistant over time.

Answer explanation

Individual horseweed plants that are resistant to the herbicide increased over time by surviving and reproducing, and passing their herbicide-resistant genes to their offspring.

Which of the following describes the trend in the female elephant population from 1970 to 1995?

• The overall population decreased, and the proportion without tusks increased.

• The overall population decreased, and the proportion without tusks decreased.

• The overall population increased and then decreased, and the proportion without tusks increased.

• The overall population increased, and the proportion without tusks decreased.

Answer explanation

The correct choice is that the overall population decreased, and the proportion without tusks increased from 1970 to 1995.

African elephants are threatened by poachers, who kill the elephants for their tusks. Both male and female elephants can grow tusks. There are some elephants that are tuskless (do not grow tusks). In the elephant population of Gorongosa National Park, the number of female elephants was monitored for many years. The graphs show the total female elephant population and the percent of tuskless females in that population from 1970 to 2015. Which of the following represents the appropriate method for calculating the number of tuskless females in the year in which the number of female elephants was lowest?

• 1000 / 0.1

• 1000 / 0.1

• 100 x 0.4

• 100 / 0.4

Answer explanation

The correct method is to divide the total number of female elephants by the percentage of tuskless females to calculate the number of tuskless females in the year with the lowest female elephant population.

In 1978, scientists studied how the fitness of marine sticklebacks would be affected if they were introduced into a freshwater environment. They collected 90 male and 90 female sticklebacks from a marine population and 10 male and 10 female sticklebacks from a freshwater population. The 200 sticklebacks were introduced into a freshwater environment that had no stickleback fish previously. Which of the following best describes the likely results of the scientists' investigation of the fitness of the sticklebacks that were originally from a marine environment?

• The fitness of the sticklebacks from the marine environment increased because their chance of survival and reproduction is greater in the freshwater environment than in the marine environment.

• The fitness of the sticklebacks from the marine environment increased because their chance of survival and reproduction is less in the freshwater environment than in the marine environment.

• The fitness of the sticklebacks from the marine environment decreased because their chance of survival and reproduction is greater in the freshwater environment than in the marine environment.

• The fitness of the sticklebacks from the marine environment decreased because their chance of survival and reproduction is less in the freshwater environment than in the marine environment.

Answer explanation

The fitness of the sticklebacks from the marine environment decreased because their chance of survival and reproduction is less in the freshwater environment than in the marine environment.

In 1978, scientists studied how the fitness of marine sticklebacks would be affected if they were introduced into a freshwater environment. They collected 90 male and 90 female sticklebacks from a marine population and 10 male and 10 female sticklebacks from a freshwater population. The 200 sticklebacks were introduced into a freshwater environment that had no stickleback fish previously. After the 200 sticklebacks were introduced into the freshwater environment, the scientists collected data on the frequency of the allele in the population from 1978 to 1985. Which of the following best describes the likely results of the scientists' investigation?

• The frequency of the allele continued to be high in approximately 10% of the individuals in the population.

• The frequency of the allele continued to be high in approximately 90% of the individuals in the population.

• The frequency of the allele in the population started very low and continued to increase over time.

• The frequency of the allele in the population started very high and continued to decrease over time.

Answer explanation

The frequency of the allele in the population started very high and continued to decrease over time.

Recently a scientist decided to repeat this study, but relocated a population of sticklebacks from a freshwater environment into a marine environment. Which of the following best predicts how the frequency of the allele would change over time if a population of sticklebacks from a freshwater environment was placed into a marine environment?

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Based on the data in the table, which of the following identifies and describes the student model that is most consistent with the data in the table?

• Student Model 1 shows that amphibians and reptiles share the most structural similarities and are the most closely related among the four groups.

• Student Model 1 shows that sharks and ray-finned fishes share some structural similarities and are the most closely related among the four groups.

• Student Model 2 shows that amphibians and reptiles share the most structural similarities and are the most closely related among the four groups.

• Student Model 2 shows that sharks and ray-finned fishes share the fewest structural similarities with amphibians and reptiles and are the most closely related among the four groups.

Answer explanation

The correct choice is Student Model 1, which shows that amphibians and reptiles share the most structural similarities and are the most closely related among the four groups.

Which of the following statements is an accurate interpretation of the labeled branch points on the model?

• Location 1 represents the common ancestor of only two of the three species.

• Locations 1 and 2 represent extinction events for G. humeralis.

• Location 3 represents the common ancestor of both G. humeralis and G. coccinatus.

• Locations 2 and 3 represent speciation events.

Answer explanation

Location 3 represents the common ancestor of both G. humeralis and G. coccinatus.

Which of the following statements is an accurate description of the evolutionary relationships shown in the model?

• G. coccinatus is more closely related to G. antillensis than to G. humeralis.

• G. antillensis has more DNA and protein sequences in common with G. humeralis than with G. coccinatus.

• G. coccinatus and G. humeralis share the most recent common ancestor, as compared to G. antillensis.

• G. humeralis is more closely related to G. coccinatus than to G. antillensis.

Answer explanation

The correct statement is that G. coccinatus and G. humeralis share the most recent common ancestor, as compared to G. antillensis.

The presence of tiny hairs, called setae, on the toe pads of some geckos is associated with the ability to adhere to smooth surfaces. This ability allows geckos to climb in areas where many predators cannot. Scientists studying the evolution of setae have identified three closely related species of gecko, only one of which can adhere to smooth surfaces. A model of the evolutionary relatedness between these species is represented in the figure. Which of the following best describes how the ability to adhere to smooth surfaces affects the fitness of G. humeralis?

• The ability to adhere to smooth surfaces is likely to decrease the fitness of G. humeralis because the ability decreases the likelihood of predation.

• The ability to adhere to smooth surfaces is likely to decrease the fitness of G. humeralis because the ability increases the likelihood of predation.

• The ability to adhere to smooth surfaces is likely to increase the fitness of G. humeralis because the ability decreases the likelihood of predation.

• The ability to adhere to smooth surfaces is likely to increase the fitness of G. humeralis because the ability increases the likelihood of predation.

Answer explanation

The ability to adhere to smooth surfaces is likely to increase the fitness of G. humeralis because the ability decreases the likelihood of predation.