Question

Hermaphroditism is often found in animals that are fixed to a surface. Motile species are less often hermaphroditic. Explain why.

Short answer

Organisms that remain attached to a substratum are often hermaphroditic because these organisms cannot move from place to place in search of mates. Due to this, independent evolutionary changes in these organisms caused changes in the sex-determination pathway.

Hence these organisms produce both male and female gametes. However, the organisms that exhibit locomotion have separate sexes because they can move in search of mates.

Step-by-step solution

Hermaphrodites

Hermaphrodites are organisms that possess both male and female gametes. These hermaphrodites may produce sperms first, and then they later produce eggs. Many plants and animals are known to exhibit hermaphroditism.

Evolution of hermaphrodites

Some organisms like plants and other animals were immotile, and hence their mating opportunities were meager. This could cause species extinction. Therefore, these organisms evolved to produce changes in the germline cells, such that both male and female gametes were produced.

Absence of hermaphroditism in motile organisms

Motile organisms lack hermaphroditism because these organisms possess structures that help them move. Such organisms have better chances of selecting mates that are well-suited for themselves. This creates genetic diversity in organisms and also helps in the continuity of species.