Question

which of the following answer choices lists the ancestors of the modern horse, in order, from the oldest that lived 60 million years ago to the most recent that lived 7 million years ago?
○ hyracotherium, mesohippus, merychippus, pliohippus, because over time, the number of toes decreased and body size increased
○ pliohippus, mesohippus, merychippus, hyracotherium, because over time, the number of toes increased and body size decreased
○ hyracotherium, merychippus, mesohippus, pliohippus, because over time, the number of toes decreased and body size increased
○ pliohippus, merychippus, mesohippus, hyracotherium, because over time, the number of toes increased and body size decreased

Explanation:

The first option correctly lists the ancestors in chronological order (oldest to most recent) as Hyracotherium (60 million years ago), Mesohippus, Merychippus, Pliohippus. Also, the trend of horse evolution shows a decrease in the number of toes (from multiple toes to a single hoof) and an increase in body size over time. The other options either have the wrong order or incorrect evolutionary trends (like increasing toes or decreasing body size).

Answer:

Hyracotherium, Mesohippus, Merychippus, Pliohippus, because over time, the number of toes decreased and body size increased.