How has the anatomy of marine mammals evolved to suit an aquatic existance?

Question

How has the anatomy of marine mammals evolved to suit an aquatic existance?

Answer 1

1. flippers insted av toes

2. blo hole muved tu top wen anamal is horizontal

     & hav flap tu keep water out

3. tael with flippers onit

4. most haer gon

5. sum hav sonar (yuze sound waves tu detekt wotz theer)

6. body shape streemlined

Answer 2

Animals that live in an aquatic environment tend to have smooth body shapes, which break the water resistance.  They do not demonstrate the profusion of appendages such as wings, limbs and other organs needed by land animals to counteract the force of gravity.  The sea provides them with enough buoyancy.  Instead, the analogous structures have developed into flippers for propulsion in the water.

The fish do not have to adapt to as many variations in climate as do land animals.  Surface water temperatures do not vary much, so the fish, whose bodies consist largely of fluid, do not require any special mechanisms for regulating their body temperatures.  Other animals, including mammals, do not have sweat glands for adapting to changing conditions in their surroundings.  They are, however, sensitive to variations in conditions, and therefore tend to stick closely to particular zones where pressure, light, temperature and amount of salt in the water are constant.  An exception to this temdency to stay within a zone are the larger animals such as the sharks and whales, which can travel freely up and down the oceans.

At levels below the 300-foot layer, the struggle for survival in fiercer, and the numbers of animals is therefore sparser.  Some of the fish have developed huge, expanding which will enable them to swallow prey larger than they are.  In this way, they can hold more food in their stomachs for a longer period of time.

Some of the fish, such as the Gigantura, have sensitive, tubular (telescopic) eyes, which enable them to see their prey in the darkness of the ocean depths.

Some of the fish, in the sparsely inhabited depths of the water depend on one chance meeting with another fish for reproduction.  The male is therefore sometimes much smaller than the female, and will attach itself permanently to the female, living off the female fish as a parasite.

Because the ocean environment is more stable than the land environment, the marine animals have not had to make as many special adaptations to their environment.  They do not exhibit the same variety that is found amoung land animals.  They also have not changed as much as land animals on an evolutionary scale.