Give an account of fresh water, egg laying and pouched mammals with suitable examples. (UPSC 2015, 15 Marks, )

ताजे पानी, अंडे देने वाले और थैलीधारी स्तनधारियों का विवरण दें उपयुक्त उदाहरणों के साथ। (Give an account of fresh water, egg laying and pouched mammals with suitable examples.)