d. both B and C

1. 1. Which of the following is a way in which variations can arise in a population? a. natural selection b. mutation c. crossing over during meiosis d. both B and C

2. d. both B and C

3. 2. Tail length in mice varies within a population. Scientists observed change in the distribution of tail lengths in a mouse population over time. At the genetic level, what has most likely happened to the allele for the shortest tail lengths? a. The allele changed from being dominant to being recessive. b. The allele changed from being autosomal to being sex-linked. c. The allele became less frequent than the alleles for longer tail lengths. d. The allele began to code for long tail lengths instead of the shortest ones.

4. c. The allele became less frequent than the alleles for longer tail lengths.

5. 3. Which of the following best describes natural selection? a. Individuals who adapt during their lifetime are more likely to survive and reproduce. b. Individuals born with certain favorable traits are more likely to survive and reproduce. c. There are little or no variations in populations, which makes adaptations rare over time. d. Individuals with little or no variation are more likely to survive and reproduce.

6. b. Individuals born with certain favorable traits are more likely to survive and reproduce.

7. 4. The frequency of an allele in a fly population changes from 89% to 20% after three generations. Which other events most likely occurred during the same time period? a. An environmental change and a fly population increase. b. An environmental change and a fly population decrease. c. Interbreeding of flies with an invasive species and fly population speciation. d. Interbreeding of flies with an established local species and fly population speciation.

8. b. An environmental change and a fly population decrease.

9. 5. If early Viking explorers in Greenland and North America had survived and become the main ancestors of early North American settlers, rather than the mixture of immigrants from across Europe and other continents, today there would be a much higher incidence of Nordic traits in the US population. Such a scenario would demonstrate a. gene flow from continent to continent. b. the founder effect. c. genetic drift among the original Viking explorers. d. directional selection.

10. b. the founder effect.

11. 6. What is the correct order of the steps regarding speciation? a. one species  geographic isolation  divergent evolution  reproductive isolation  two species b. one species  reproductive isolation  divergent evolution  geographic isolation  two species c. one species  divergent evolution  geographic isolation  reproductive isolation  two species d. one species  geographic isolation  reproductive isolation  divergent evolution  two species

12. d. one species  geographic isolation  reproductive isolation  divergent evolution  two species

13. Use the diagram below to answer questions 7-8. 7. The similarity of these structures suggests that the organisms a. have a common ancestor. b. evolved slowly. c. all grow at different rates. live for a long time.

14. a. have a common ancestor.

15. 8. An analysis of the DNA from these organisms would indicate that a. their DNA is identical. b. they all have tails. c. their DNA sequences show many similarities. d. they all have the same number of chromosomes

16. c. their DNA sequences show many similarities.

17. 9. Bulldogs have been bred by humans for increasingly large heads. This has made the birthing process more difficult for the mother, and may decrease survival among newborn pups. This intentional breeding is an example of a. natural selection. b. founder effect. c. genetic drift. d. artificial selection.

18. d. artificial selection.

19. 10. What is the difference between a variation and an adaptation?

20. Variations are little differences within a population that play no role in fitness. • Adaptations play a role in fitness, and everyone within a population exhibits the trait.