Question

The group of amniotes includes
A. Reptiles and birds
B. Birds and Mammals
C. Fishes and amphibians
D. Reptiles and mammals

Answer 1

Hint: The anamniotes lack the amnion. Apart from this feature, the amniotes are also characterized by laying eggs in water but some of them lay eggs on land.

Complete Answer:
- They are vertebrates that do not belong to the clade Amniota. Amniota is a group of vertebrates that consists of reptiles, birds, and mammals.
- During their embryonic or fetal stage, they have an amnion. The amnion is a membrane that surrounds the embryo or fetus as it grows or develops.
- The amnion and the chorion form the amniotic sac. The sac is fluid-filled and the fluid is referred to as amniotic fluid. This fluid serves as a shock absorber preventing physical injury to the growing fetus.
- Anamniota is a group of vertebrates without amnion (the innermost of the extraembryonic membranes forming a fluid filled sac around the foetus in amniotes). It includes cyclostomes, fishes and amphibians.

Thus, the correct option is C i.e. Fishes and amphibians.

Note: Vertebrates that develop without the extra-embryonic membranes are known as amniotes. They do not belong to a formal classification group, because they are associated by the absence of a characteristic. Among the tetrapods, anamniotes include extinct amphibians and two groups of extinct reptile animals such as anthracosaurs and brachiosaurus.