SAT Subject Biology Practice Question 365: Answer and Explanation

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Question: 365

15. In 1910, a small town on the East Coast of the United States relied primarily on agriculture to support its economy. In the mid-1930s, a steel mill was built, and the economy shifted from being agriculturally supported to being industrially supported. The steel mill released a lot of smog and soot into the air, which collected on the bark of trees in a wooded area near the outskirts of town. Over a period of ten years the bark gradually darkened, then maintained a constant dark color.

A variety of animals and insects lived in the wooded area. In particular, a certain species of moth served as the primary food source for a population of birds. The moths lay their eggs in the bark of the trees and, thus, must spend a fair amount of time sitting on the tree trunks. Table 1 presents data on the moth population.

Table 1

If a seed from one of the trees was planted in an area far from the st

A. Black, because the parent tree had black bark
B. White, because the gene causing black bark was mutated due to environmental pollution
C. Black, because the gene causing white bark was mutated due to environmental pollution
D. White, because the black bark was an acquired characteristic and is therefore not passed on to progeny
E. The color of the bark is not able to be determined.

Correct Answer: D


D The original parent had white bark. The change in bark color is the result of an accumulation of soot on the tree. This is an acquired characteristic and would not be passed on to offspring. Seedlings that grew far from the plant would not be exposed to soot in the air and would not experience discoloration of their bark.

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