Q.Distinguish between Prototheria, Metatheria and Eutheria, giving one example of each.

Step 1. Prototheria is the small, egg-laying group of mammals — despite belonging to class Mammalia, they are oviparous, laying eggs rather than giving birth to live young; Ornithorhynchus (the duck-billed platypus) is the standard example.

Step 2. Metatheria gives birth to live young, but at a very immature stage of development; the young then complete their development attached inside an external pouch, the marsupium, on the mother's body; Macropus (the kangaroo) is the standard example. …

Order the three mammalian sub-groups by their mode of reproduction/development, from egg-laying through pouched to f …

• Assuming all mammals are viviparous — Prototheria is a genuine egg-laying exception within the class. …