Monday, April 15, 2013

Marine Life and the Ecosystem

By Alex Asher


There are thousands of species of marine life, from tiny zooplankton to enormous whales. Each is adapted to the specific habitat it occupies. Fish can drink salt water, and eliminate the salt through their gills. Seabirds also drink salt water, and the excess salt is eliminated via the nasal, or "salt glands" into the nasal cavity, and then is shaken, or sneezed out by the bird. Whales don't drink salt water, instead getting the water they need from the organisms they eat.

Many marine mammals live in very cold water. They have blubber to insulate their bodies and keep them warm in the cold ocean waters. Blubber is a really thick layer of fat between the animal's skin and inside organs. It is very effective at keeping an animal warm. The gray whale's layer of blubber is about 10 inches thick!

Whales, dolphins, porpoises, walruses, manatees, dugongs, seals, and sea otters are all mammals that live in the ocean. Some, like seals and sea otters, can also live on land, but they spend most of their time underwater. These animals have lungs, are warm-blooded, give birth to live babies (they don't lay eggs) and nurse their babies, but they live in salt water instead of on dry land like most mammals. Since they have lungs, they need to breathe air instead of just getting oxygen from the water like fish and other ocean animals can. Instead of breathing air through their mouth or nose like we do though, a whale or dolphin uses a special hole on the back of its head called a blow hole to get air from above the surface of the water. Then it dives back down into the water and swims around for a few minutes before it needs to come up to breathe again. When it does, it breathes out the air through the blow hole and then breathes in more air so it can go back under the water again. When the air goes out of the blow hole, there is usually some water that squirts out with it, making a little spray at the surface (like the killer whale in the picture). Marine mammals also have some fur or hair, but sometimes it falls out by they time they become adults.

Sharks have several rows of sharp pointed teeth and powerful jaws to tear off big pieces of food, which they swallow whole. They don't even need to chew their food! Sometimes sharks lose teeth, but when they do, new ones grow in their place. Sharks have several rows of teeth. They eat bony fish, squid, marine mammals, and even sea turtles. They have an excellent sense of smell, which helps them find food. Many sharks eat near the surface of the water, but will also dive down deeper in search of food.

Marine mammals need to come to the water surface to breathe, which is why the deep-diving whales have blowholes on top of their heads, so they can surface to breathe while keeping most of their body underwater. Whales can stay underwater without breathing for an hour or more because they make very efficient use of their lungs, exchanging up to 90% of their lung volume with each breath, and also store unusually high amounts of oxygen in their blood and muscles when diving.




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