1.9.2 Natural Selection in Action

Question 1

natural selection

Answer 1

• involves a change in the frequency of certain traits in a population over time.

Question 2

selective pressures

Answer 2

• determine which traits are favored and which are selected against. For example, predation can exert a selective pressure.

Question 3

During the Industrial Revolution, the whitish lichen which colored the trees died, leaving the trees a brown bark color. The dark variety of the peppered moth became more able to evade predators because it blended into the darker colored trees. At the same time, the light variety became more conspicuous to predators. Given this scenario, which of the following statements is incorrect?

Answer 3

• If the pollution problem was remedied, and the trees returned to their natural state, the dark moths would remain more numerous.

Question 4

A population of bacteria is resistant to penicillin, even though the population was not resistant to the antibiotic when it was first introduced. Which of the following explanations for this phenomenon is consistent with evolutionary theory?

Answer 4

• There were probably some resistant bacteria in the population before penicillin was used

Question 5

True or false?

Natural selection involves a change in the frequency of certain traits in a population over time.

Answer 5

• true

Question 6

Which of the following cannot exert a selective pressure?

Answer 6

• All of the above can exert selective pressure on an organism.

Question 7

Which of the following statements about natural selection is incorrect?

Answer 7

• It can alter the characteristics of an individual during his/her lifetime.

Question 8

Changes in the ecosystem in which an organism lives cause

Answer 8

• individual organisms that are already more suited to the new ecosystem to reproduce with greater frequency.
• individual organisms that are not well suited to the environment to reproduce with reduced frequency