Which is a common adaptation for mammals in a aquatic environment?

Answer 1

Marine mammals have developed a variety of adaptations in order to live in water. First, in order to swim efficiently, their bodies have become streamlined. Their front legs have been shortened to flippers, and the toes have fused together. The back legs have been greatly reduced such that (except in fur seals and sea lions) they could not be used for walking on land. Except for fur seals, there is little fur to slow down swimming. Testes do not go outside the body; they are either in a pocket or internal. In pinnipeds, the mammary glands are within a pocket as well. Ears have gone inside the head; they are external only in fur seals and sea lions, and in these cases, they are small. Also, as many marine mammals live in cold climates, there must be some way to keep warm. This is usually done by a layer of fat (aka blubber). The milk that female marine mammals produce is high in fat so as to build up this layer of fat in the pups. The lungs of sirenians are not divided into lobes and are as long as the spinal column so that the sirenians can be buoyant in the water and can remain in a horizontal position. The nostrils of marine mammals only open by voluntary muscles, so water does not rush in when the animal is diving. Cetaceans have blowholes on the top of their heads, so that they can be almost entirely underwater but can still breathe. The various marine mammals have developed different methods of sleeping. Sirenians and earless seals sleep by having very relaxed periods, in which they have little movement other than coming up to the surface to breathe whenever necessary (all marine mammals can stay underwater without breathing for a long time). Cetaceans, fur seals, and sea lions sleep by resting one hemisphere of the brain at a time while the other hemisphere is awake. In order to protect the eyes from water, pinnipeds have clear membranes that cover the eyes during diving, while cetaceans constantly produce tears to keep the water out. Toothed whales, dolphins, and porpoises are known to echolocate: they produce clicking sounds, and can discern the presence, shape, size, and distance of objects by the echoes, bouncing off the object. The other marine mammals can hear underwater, but probably do not echolocate. Finally, in order to reproduce and give birth, pinnipeds simply go to land (although walruses may mate in water). However, cetaceans and sirenians reproduce and give birth in water. Cetaceans may need a third individual to hold the other two in place because copulation is hard underwater. Ceatceans give birth tail first, but sirenians give birth head first.

My above answer included only cetaceans (whales, dolphins, and porpoises), pinnipeds (fur seals, earless seals, sea lions, and walruses), and sirenians (manatees and dugongs). It did not include the Sea Otter, which is also a marine mammal. Sea otters are a recently marine species, so they have not developed many of these adaptations. They sleep by floating on their backs. They are covered in thick fur and have normal mammalian limbs. They have external ears. Their back feet are webbed, and their front feet are shaped like mittens. However, they mate and give birth in the ocean. They are somewhat streamlined with their short limbs

Answer 2

Aquatic animals have many adaptations that allow them to survive in their water habitat including gills, scales, dorsal fins, transparent eyelids,et cetera.

Answer 3

Hairlessness, blubber, increased hair density with with water proof oily coating, stream lined body contours. The ability to close nares when submerged are several adaptations.

Answer 4

Streamlined body