1. Chimpanzees exhibit 99% genetic similarity to humans. Cows share approximately 80% of their DNA sequence with humans. Scientists can predict the relative age of a common ancestor using DNA sequences. Which of the following statements regarding molecular clocks is true?
A. Molecular clocks cannot provide information regarding the relatedness of organisms or how distantly related common ancestors are from descendant species.
B. Chimpanzees, humans, and cows were at one time more closely related, but due to genetic drift have become more distantly related from one another.
C. Cows do not share a common ancestor with chimpanzees and humans, and any genetic relatedness is by chance.
D. The common ancestor of chimpanzees and humans lived more recently than the common ancestor of cows, chimpanzees, and humans.
E. The common ancestor of cows, chimpanzees, and humans lived more recently than the common ancestor of chimpanzees and humans.
2. Researchers often use mice to evaluate potential medications for treating human disease. If a medication is successful in the mouse model, it then must be further tested in human clinical trials. Which of the following best explains why clinical trials are necessary?
A. Mice are much smaller than humans.
B. Mice and humans evolved independently of one another.
C. Mice and humans have very different biochemistries.
D. Mice and humans live in different environments.
E. Mice and humans have only 80% genetic similarity.