State reasons for each of the following: Echidna and platypus lay eggs but are considered as mammals. Forelimbs of birds are modified. Crocodiles have four-chambered heart but are still reptile

[AmarCBSE]

State reasons for each of the following:

1. Echidna and platypus lay eggs but are considered as mammals.
2. Forelimbs of birds are modified.
3. Crocodiles have four-chambered heart but are still reptiles.

Answer:

1. They have mammary glands for the production of milk to nourish their young ones.
2. To reduce body weight for flight, forelimbs of birds are modified.
3. Crocodiles are cold blooded, lay eggs and have scale on their body. These characteristics make ’ them reptile.