When majority of the marine animals are laying eggs, how certain specific species(e.g. whale) are mammals?

Answer 1

It's important to understand that, as mammals, whales had to evolve from land mammals (as mammals originally arose on land).

Some people find that hard to believe, but there is plenty of evidence from: (1) fossils; (2) from the fact that modern whale skeletons have hip- and rear leg-bones, five fingerbones in the flippers, etc.; (3) from other morphological features, such as the whale's mammalian inner ear; (4) from embryology (whale embryos have legs); (5) genetics and molecular analysis of DNA from whales and other species (like hippos); and (6) many other things (see sources ... or ask, and I can elaborate more).

So with the existence of other marine mammals, like seals, sea lions, walruses, manatees, dugongs, sea cows, dolphins, etc. ... it is not that surprising that some marine mammals would have evolved as far as whales have.

Answer 2

Gestating the offspring inside the body of the female offers significant more protection to the young than laying eggs that can be eaten. The young hatchlings are also vulnerable to predators. The trade-off is that the mammal produces far fewer young per period.

Answer 3

The ones who are mammals are the ones giving live births like the whale that you mentioned. Turtles are reptiles, and there are other species classifications as well, but the ones that give live birth and breathe air are mammals.

Answer 4

Mammals are just more advanced in their evolution and so higher speices give birth to live young because they have uterus etc, while more primitive animals do not so must lay eggs

Answer 5

Mammals are classified because they have hair on their bodies and they nurse their young with mammary glands.