USA Biology Olympiad (USABO) Practice Exam

A fruit characterized by a sclerenchyma cell endocarp and fleshy mesocarp and exocarp is classified as what type?

1. Berry

2. Pome

3. Drupe

4. Aggregate fruit

The correct answer is: Drupe

The correct classification of a fruit with a sclerenchyma cell endocarp and a fleshy mesocarp and exocarp is a drupe. Drupes are defined by having a hard, stony covering (the endocarp) that surrounds the seed, alongside a fleshy layer (the mesocarp) and the outer layer (the exocarp). Common examples of drupes include cherries, peaches, and olives, where the pit is the hardened endocarp containing the seed. The presence of sclerenchyma cells in the endocarp indicates that it has a more rigid structure, which is typical for drupes. In contrast, while berries and pomes may also have fleshy tissues, they have distinct structural features that do not match the description provided. Berries, for instance, typically have a thin outer skin without a hard endocarp, and pomes have a structure that includes a core which distinguishes them from drupes. Aggregate fruits are formed from multiple ovaries of a single flower and do not fit the description of having a single endocarp surrounding the seeds.