Question

A biologist conducting a long-term field study noticed there were two types of mice in a valley. One type of mouse had webbed toes, and one type of mouse lacked webbed toes. A dam was built in the valley turning the land into a wetland. As the years passed, all mice living in the valley were found to have webbed toes. No mice were found with non-webbed toes.


Which statement best explains the observed change in the mouse population


Select an answer

A.
Webbed toes in mice are controlled by the environment.


B.
The mice grew webbing to move more efficiently in the new environment


C.
Webbed-toed mice survived better and reproduced more than mice without webbed toes


D.
The increased water levels in the valley increased the mutation rate in the mouse population.

Answer 1

C. The webbed-toed mice had a survival and reproductive advantage in the new wetland, so their genes became more common by natural selection.

Explanation: Traits aren't acquired within an individual lifetime (B) nor produced directly by the environment (A). Random mutations (D) would not specifically increase only webbing in response to flooding. Natural selection causes advantageous heritable traits to increase in frequency.