Difference between Mammals and Cetaceans
Mammals are characterized as air breathing vertebrates with sweat glands, hair and three middle ear bones. Female mammals possess mammary glands that produce milk. Mammals are members of the class mammalian. These are warm blooded animals. Cetaceans are nothing other than mammals who have adapted themselves to aquatic life. Cetaceans mainly include dolphins, whales and porpoises. Although cetaceans are mammals and can communicate with their land locked cousins, there are many differences between mammals living on dry land (terrestrials) and those adapted to living in the water: cetaceans. They differ in their means of locomotion, basic body structure, food and the ways in which the most basic tasks like breathing are done.
Morphology
Cetaceans have a spindle shaped body. They have flippers to push them through water, which are the modifications of forelimbs. Hind limbs have reduced size and are not attached to the backbone. Body of a cetacean is covered with a thick layer called blubber as a protection from cold water in the sea. Terrestrialmammals and even whales have seven bones in the neck. Hind limbs play a major role in locomotion. Some mammals have adapted themselves to walk on two hind limbs as in case of humans. Some species have elongated backbone that erupts out in the abdomen behind the body. For some case (monkeys) it is very useful in maintaining balance.
Respiration
Mammals have advanced spongy lungs with large surface area greater than the outer area of lungs themselves. They breathe with the help of diaphragm that separates thorax from the abdomen. When it contracts lungs stretch increasing the volume and air flows inside. Very tiny air sacs that have millions of blood vessels on their surface absorb oxygen and deoxygenated blood is purified. The rib cage that protects the lungs itself has a flexible nature due to use of cartilage in the sternum. Cetaceans come to the surface at equal intervals of time to exhale carbon dioxide. Exhaled air condenses which appears as steam. Blowholes, name used for nostrils close with a muscular action for the time cetaceans are under the water. It is due to these physiological adaptations that cetaceans are capable of swimming under water for much longer time intervals than other mammals.
Feeding
Some species in cetaceans have teeth to catch smaller fish. These are not used to chew but chunks of flesh are swallowed. Teeth may be used to tear large prey into smaller chunks. Others such as Mysticeti have these baleen plates hanging down from the upper jaw to filter small animals out. Terrestrial mammals can either be carnivorous - those who eat other animals or herbivores – those who are sustained from the nutrition provided by plants. Herbivores serve as host to some bacteria that digest complex material like cellulose. Carnivorous species include insectivorous mammals - those who feed on insects.
Summary
Mammals
- Mostly have seven bones in the neck.
- Hind limbs play a major role in locomotion.
- Some may have tail.
- Breathing is done with help of diaphragm.
- Spongy lungs with large surface areas.
- Can be carnivorous or herbivores.
Cetaceans
- Have larger brains than their terrestrial cousins.
- Have a spindle shaped body
- Have modified forelimbs called flippers.
- Have muscular blowholes that help to remain under water.
- Swallow other fish.
- Some have baleen plates hanging from upper jaw to filter small fish.
