Question

Animal like whale , walrus lives in water (ocean). Whether they are included in pisce or mammalia

Answer 1

Only because they live in water, doesn't mean that they are pisces. Whales, walrus do not lay eggs like Pisces, they give birth to offsprings just like mammals. Moreover, they don't have scaly skin like pisces.

Answer 2

animal like whale, walrus lives in water but they are included in mammalia because they have four chambered heart and their body structure is more complex