There are several aspects of marine biology. Some of these tend to be very boring and take several trials and repetitions before you can come up with a definite conclusion or results. If you, however, study mammals instead, you may realize that research tends to become more interesting and easier, since these animals react very quickly. You will have more data to gather and observe, thereby providing you the opportunity to enhance your skills.
The 3 Orders
Marine mammals are generally grouped into 3 orders. The order Cetacea includes dolphins, whales and porpoises. The order Pinnipedia involves walruses, seals and sea lions. The order Sirenia includes dugongs and manatees.
The whole lifecycle of the order Cetacea is aquatic. There are a couple of sub-orders founded on the feeding mechanism, namely Odonticeti and Mysticeti. The order Pinnipedia involves part of their lifecycle being terrestrial. The word Pinnipedia means “feather-footed” since the animals possess 4 webbed fins. These can be found in all oceans, but most reside at high latitudes, traveling usually in herds and carrying out very long migrations. The order Sirenia usually spends their whole lifecycle in the water. These are the only aquatic animals that eat plants mainly.
The Suborders of Cetacea
The sub-order Mysticeti includes baleen whales and blue whales. These animals use baleens or brush-like triangular continuously renewing plates that hang from the roof of the mouth, with 480 plates on each jaw side. The plates filter zooplankton, squid and small fish, with the tongue moving the food into the throat.
Right whales are skim feeders, grey whales feed via a suction mechanism on animals living on the bottom of the ocean and minke whales feed by gulping and lunging. Different whales use various approaches to eat successfully. The sub-order odonticeti includes mammals that have their first teeth remain until they die. These grasp and swallow whole prey. A good example is the killer whale.
About the Pinnipeds
Pinnipeds have a low SA/V ratio and develop insulation via their hair and blubber. Fur seals can have so many hair belonging to either underfur fibers and guard hairs. These all moult, especially during the summer after breeding period, while others just remain out of the water until complete. Pinnipeds exhale before deep dives and have high myoglobin and hemoglobin concentrations. These animals feed usually on fish and squid. The walrus will use their tusks to dig for animals living on the bottom.
The Sirenia
Sirenians are distributed widely but are usually caught for their hides, meat and oil. They are particularly prone because they are placid and slow moving. Danger comes mainly from powerboats at present and their loss of habitat. These animals are very social but now prefer to go in family groups or alone.
Dugongs are usually found in the Pacific and Indian Ocean. Manatees can be found in Atlantic coastal waters. Sireneans inhale before they dive into the water, just like whales. These can dive for 10 to 20 minutes. Bristles can detect food to help themselves tide over the lean months.