Question

You are at the aquarium looking at a freshwater mammal tank and a manatee swims close to the glass. On his front flippers you see fingernails. You think, what possible use could fingernails be to a manatee, then you realize they are of no use at all. Which of the following best explains the presence of fingernails on a manatee?
A. they are remnants of the bones used by fish for their fins.
B. they are homologous structures.
C. the bones are protruding from the fins and only look like fingin the tank looks like it has fingernails.
D. convergent evolution has occurred.
E. they are vestigial structures.

Answer 1

The fingernails on the manatee are homologous structures.

Explanation:

The manatee is an animal that lives in the water, but it is not an animal that is related to the fish, instead it is a mammal. When the term mammal is mentioned, people often think of terrestrial animals, but some of the mammals are not living in the water, and have lot of characteristics that are very similar to the other marine animals. Mammals that live in water are:

• manatee
• whales
• seals
• walrus

Some of these mammals, like the manatee, actually have fingernails, which is very weird considering that they are of no use. The fingernails are actually homologous structures, or rather structures that have been kept from their ancestors, and can be found at many other animals with which they share common ancestor. While the ancestors of the manatee were terrestrial mammals, over time they totally transformed as they were using the water more and more, but the fingernails remained, with the main reason for that being that they are not disadvantageous, so there is no evolutionary pressure for the animal to lose them.

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