The moth species Biston betularia has two color morphs, or variants. One has a speckled white and black color, while the other is all black. In the early 1800s in England, the distribution was 10,000 speckled morphs to 1 black morph. That distribution changed dramatically between 1900 and 1950. By 1950, the distribution of the speckled morph had declined to less than 3% of the population and the black morph distribution increased to 97%. Which statement most likely explains this change?

A. A predator of the moth underwent steep decline, which reduced selective pressures on the moth.

B. A chance mutation occurred in one black individual, which gave an advantage to the black morph's ability to survive.

C. The changes are due to normal random fluctuations that might be observed in any population over time.

D. Changes in the environment changed each morph's ability to evade predation in different ways.

Question

Biology

Markus Richard

14 March, 22:09

The moth species Biston betularia has two color morphs, or variants. One has a speckled white and black color, while the other is all black. In the early 1800s in England, the distribution was 10,000 speckled morphs to 1 black morph. That distribution changed dramatically between 1900 and 1950. By 1950, the distribution of the speckled morph had declined to less than 3% of the population and the black morph distribution increased to 97%. Which statement most likely explains this change?

A. A predator of the moth underwent steep decline, which reduced selective pressures on the moth.

B. A chance mutation occurred in one black individual, which gave an advantage to the black morph's ability to survive.

C. The changes are due to normal random fluctuations that might be observed in any population over time.

D. Changes in the environment changed each morph's ability to evade predation in different ways.

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Answers (1)

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London Beard · Answer 1

I think this one might be D. I used the process of elimination for this.

A: If the predator began to die out, then both morphs would have grown in population.

B: Changes in mutation usually happen over a greater period of time than just 50 years.

That leaves C and D. I know nothing of the normal random fluctuations, so I can't say for sure that this is right. Therefore, my mind views D as the right answer.

While mutation occurs over a great span of time, a change in environment can happen faster, and often kills off some species since they don't have the tools for survival.