Marine Life and the Ecosystem

By Alex Golfing


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.

Some animals that have the word "fish" in their names are not really fish. Some examples are cuttlefish (they are mollusks, see below), jellyfish (they are actually plankton), and starfish (they belong to a group called "echinoderms"). Can you think of any other animals that are called fish but do not have the things it takes to be a real fish?

Some creatures that live in the ocean use a special chemical reaction inside their bodies to create a glowing light. The light is called bioluminescence and happens when certain chemicals mix together, along with some oxygen from the water, in a particular part of the animal's body.

Because many bioluminescent animals live far down in the oceans where it is very dark (since sunlight cannot travel down that far through the water), the lights they make work sort of like a night light and help them see where they are going and to find food as well as other creatures to mate with. The anglerfish is an example of a deep sea creature that uses bioluminescence to find food. It has a glowing "lure" that extends from its head and dangles above its mouth. Other fish think the lure is food, but when they try to eat it, the anglerfish eats them instead!

Not all sharks are large. Some only grow up to 7 inches long. However, most kinds of sharks grow to about 5-7 feet long, which is about the same height as an average adult. Not all sharks are dangerous to humans, either. There are over 350 kinds of sharks, but only about 25 of those have ever been known to attack humans. When sharks do attack people, it is probably because they mistake people for seals or other large ocean animals that they would like to eat. It is hard for them to tell what's what from below the surface of the water.




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