Question

the fossil record indicates that the earliest known ancestor of horses has four toes. modern horses have only one. which of the following best explains why this occurred?
○ because the ancestors did not use all of their toes, their offspring were born with fewer toes.
○ gradually, over the course of many generations, the four toes merged together to form a single toe.
○ environmental pressures selected for four toes over one dominant central toe over millions of years.
○ over the course of a lifetime, ancestors would lose toes due to the stresses of prairie life, such as predation and injury.
○ offspring with genetic mutations resulting in fewer toes were more likely to survive and reproduce.

Explanation:

This aligns with natural selection: genetic variations (mutations) that improve survival/reproduction (e.g., fewer toes aiding running on open plains) become more common over generations. Other options are incorrect (e.g., disuse inheritance is Lamarckian, not evolutionary theory; merging toes without selection lacks mechanism; lifetime toe loss isn’t heritable).

Answer:

Offspring with genetic mutations resulting in fewer toes were more likely to survive and reproduce.