Question

select the correct statement(s).
the size of each genus got larger over time.
the genus equus is closely related to pilohippus. we know this because they have the most similar anatomical features.
the size of the molar chewing surface got smaller over time.
the modern day horse has 4 toes compared to the primitive horse.
a living genus can share ancestors with a genus that is now extinct.

Explanation:

• Statement 1: The size of each genus did not uniformly get larger over time. For example, there are variations in the evolutionary history of horse - like species.
• Statement 2: Equus (modern horse) is closely related to Pliohippus. They share many anatomical similarities such as certain skeletal structures that are indicative of a closer evolutionary relationship.
• Statement 3: The size of the molar chewing surface actually got larger over time. As horses evolved, their diet changed (e.g., from browsing to grazing), and larger molar chewing surfaces were selected for to handle tougher plant material.
• Statement 4: The modern - day horse has 1 toe (the hoof), while the primitive horse (e.g., Eohippus) had 4 toes on the front feet and 3 toes on the hind feet.
• Statement 5: In evolutionary biology, it is common for a living genus to share ancestors with an extinct genus. Evolutionary lineages branch, and some branches (genera) go extinct while others (living genera) continue, but they all have a common ancestor at some point in the past.

Answer:

The genus Equus is closely related to Pliohippus. We know this because they have the most similar anatomical features. A living genus can share ancestors with a genus that is now extinct.