Question

which of the following resulted from a genetic variation that was favored by natural selection?
a. cancer in a lab rat
b. smoothness of a river rock
c. the long neck of a giraffe
d. the small size of a chihuahua

Explanation:

• Option A: Cancer in a lab rat is a disease, not a result of natural selection favoring genetic variation.
• Option B: Smoothness of a river rock is due to erosion (a physical process), not genetic variation and natural selection.
• Option C: The long neck of a giraffe is a classic example of natural selection. Giraffes with longer necks (a genetic variation) could reach more food (leaves high in trees) and were favored, leading to the trait becoming common.
• Option D: The small size of a Chihuahua is due to artificial selection (human - directed breeding), not natural selection.

Answer:

C. the long neck of a giraffe