Question

Which reproductive adaptation is characteristic of most terrestrial vertebrates but not of most aquatic vertebrates?

• A. External development
• B. Internal fertilization
• C. External fertilization
• D. Motile gametes

Answer 1

The correct option is B Internal fertilization

External fertilisation occurs when gametes fuse outside the body of an organism, in a medium such as water. It is a characteristic feature of most sexually reproducing aquatic organisms. It is rarely seen in terrestrial organisms.

Most terrestrial enzymes undergo internal fertilisation in which the gametes fuse within the body of an organism, the female in case of unisexual organisms. Internal fertilisation is rare in aquatic organisms.

In all vertebrates, be it terrestrial or aquatic, the male gametes are always motile.

External development, i.e, development of the embryo outside the body of an organism, is a characteristic feature seen in most aquatic organisms, except for aquatic mammals. Amongst terrestrial organisms birds and certain reptiles exhibit external development whereas mammals strictly show internal development.

(B) Internal fertilization