8.11–8.17: Through natural selection, populations of organisms can become adapted to their environments.

When there is variation for a trait, and the variation is heritable, and there is differential reproductive success based on that trait, evolution by natural selection is occurring.

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Question 8.19

Maze-running behavior in rats:

  • a) is too complex a trait to be influenced by natural selection.
  • b) is a heritable trait.
  • c) is not influenced by natural selection, because it does not occur in rats’ natural environment.
  • d) shows no variation.
  • e) is influenced primarily by mutation.

Question 8.20

A fossil is defined most broadly as:

  • a) the preserved pieces of hard parts (e.g., shell) of extinct animals.
  • b) any preserved remnant or trace of an organism from the past.
  • c) the preserved bones of vertebrates.
  • d) a piece of an organism that has turned into rock.
  • e) the product of preservation of intact animal bodies.

Question 8.21

Which of the following statements about marsupials is correct?

  • a) They fill many niches in Australia that are occupied by placental mammals elsewhere.
  • b) They are less fit than placental mammals.
  • c) They have become extinct as a result of the greater fitness of placental mammals.
  • d) They are more closely related to each other than to placental mammals.
  • e) Both a) and d) are correct.

Question 8.22

What can be concluded from comparing differences in molecular biology between different species?

  • a) Extremely different species are fundamentally unrelated in any way.
  • b) Only DNA sequences can be used to compare species’ relatedness.
  • c) Birds are more closely related to humans than dogs are.
  • d) Genetic similarities and differences demonstrate species relatedness.
  • e) The longer two species have been evolving on their separate paths, the fewer the genetic differences between them.

Question 8.23

Evolution:

  • a) occurs too slowly to be observed.
  • b) can occur in the wild but not in the laboratory.
  • c) is responsible for the increased occurrence of antibiotic-resistant bacteria.
  • d) does not occur in human-occupied habitats.
  • e) None of these statements are correct.