Natural Selection & Artificial Selection (College Board AP® Biology)

Exam Questions

24 mins10 questions
1
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Scientists studied the effects of a drought on a population of seed-eating finches living on an island in the Galapagos. They assessed beak depth data prior to the drought, collected in 1976, and compared it to beak depth data recorded after the drought in 1978. Their results are shown in Figure 1 below.

Two bar charts compare beak depths of 1976 and 1978 finch offspring. Y-axis shows number of individuals; x-axis shows beak depth in millimetres.
Figure 1. Beak depth in finch offspring in 1976 and 1978.

Which of the following is the most likely explanation for the results shown in Figure 1?

  • Finches with the mean beak depth in 1976 had the greatest reproductive fitness after the period of drought.

  • Plants that produced smaller seeds were killed by the drought, changing the favorable beak phenotype.

  • The finch population in 1976 had little phenotypic variation, limiting the rate of natural selection.

  • The drought caused a mutation in the gene for beak length in finches, resulting in a new favorable phenotype.

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African lions face challenges in their natural habitat, including competition for food, a hot climate and limited water sources. These factors contribute to population regulation. Which of the following best describes these challenges in the context of natural selection?

  • Artificial selection pressures

  • Evolutionary fitness indicators

  • Environmental factors

  • Phenotypic variations

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The rock pocket mouse (Chaetodipus intermedius) is found in rocky areas of the southwestern United States and Mexico. These mice typically have a light-colored coat that blends with the rocks in their habitat. However, in some areas with dark lava rocks, populations of dark-colored mice are found. Researchers conducted a study to investigate the relationship between rock color and mouse coat color. They surveyed mouse populations in four different locations with varying proportions of dark lava rock coverage. Figure 1 shows the results of their study.

Scatter plot showing the percentage of dark-coloured mice relative to dark lava rock coverage, with data points increasing from left to right.
Figure 1. The relationship between mouse coat color and dark lava rock coverage.

Which of the following best explains the relationship observed in Figure 1?

  • Researchers carried out artificial selection to breed dark-colored mice.

  • The abiotic environment is fluctuating, resulting in natural selection.

  • Natural selection is acting on phenotypic variation in the mouse population.

  • Natural selection is acting on phenotypic variation in the predators of the mouse population.

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A breeder is interested in improving the sprinting speed of racehorses. They test the speed of two groups of horses over five generations. Group A consists of horses selectively bred for sprinting, while group B consists of randomly selected horses. The table below shows the average sprint speed for each group across five generations:

Generation

Average sprinting speed (m/s)

Group A

Group B

1

15

14

2

16

14

3

17

14

4

18

15

5

19

15

Which of the following conclusions can be drawn from the data?

  • All offspring that are selectively bred have alleles for fast sprinting speed.

  • Random breeding increases sprinting speed at the same rate as selective breeding.

  • Selective breeding increases sprinting speed at a higher rate than random breeding.

  • Sprinting speed does not change over time in randomly bred horses.

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Climate change is affecting the phenology (timing of life cycle events) of many species, an observation that some scientists believe could be driven by natural selection. Researchers studied the effects of warming temperatures on the egg-laying dates of great tits (Parus major) in the Netherlands between 1955-2012. They also monitored the peak abundance of winter moth caterpillars, the primary food source for great tit chicks. Figure 2 shows the results of their long-term study.

Line graph showing average spring temperature in the Netherlands and timing changes from 1960 to 2010 for caterpillar abundance and great tit egg-laying.
Figure 2. Changes in dates of peak caterpillar abundance and average egg-laying date in great tits over time.

Which of the following correctly describes the data in Figure 2?

  • The average spring temperature increased at an average rate of around 0.14 °F year-1 across the period of the study.

  • The date of peak caterpillar abundance is always earlier in the year than the average egg-laying date of the great tits.

  • The average great tit egg-laying date in 2010 is April 1st.

  • Caterpillar abundance and average egg-laying date of great tits become earlier each year at the same average rate.

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