Question

The greatest evolutionary change enabling the land vertebrates to be completely free from water habitat is the development of

• A. Four legs
• B. Four chambered heart
• C. Internal fertilization
• D. Lung

Answer 1

Answer: (C)

Internal fertilization

Internal Fertilization: In mammals, reptiles, birds, and some types of fish, the gametes meet inside of the female's body. This is called internal fertilization. All land dwellers need to fertilize this way because sperm still prefer swimming to walking.

Internal fertilization made it possible for the land vertebrates to be independent of water and thus, is a milestone in evolution.