question_answer

  (a) State two characteristic features of vertebrates. (b) State reasons for each of the following statements (i) Echidna and Platypus lay eggs but considered as mammals. (ii) Forelimbs of birds are modified. (iii) Crocodiles have four-chambered heart but are still reptiles.

Answer:

  (a)Vertebrates have coelomic body cavity, notochord  and dorsal nerve chord. (b)Platypus and Echidna are two exceptions in class-Mammalia. They have notochord and dorsal nerve chord like mammals. But unlike mammals they lay eggs. Whereas mammals give birth to young ones.