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?
Sharks look a lot like marine mammals, but they are actually fish! Unlike most fish though, sharks do not have bones. Their skeletons are made up of cartilage instead of bones. Cartilage is the same stuff that makes your ears and the tip of your nose have their shape and be a little bit flexible. Even though they don't have bones, sharks do have lots of other similarities to bony fish. They are cold-blooded and breathe through gills instead of through lungs. Sharks have gills on each side of their heads. As they swim, water passes over the gills and oxygen flows in from the water.
Most kinds of whales live in groups called pods. The pods are kind of like families. The older whales take care of the younger whales, which are called calves. Whales stay together in their pods for most of their life. Most kinds of whales live somewhere in the middle of the ocean so that they can quickly get to the surface since they need to go up for air a lot.
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.
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?
Sharks look a lot like marine mammals, but they are actually fish! Unlike most fish though, sharks do not have bones. Their skeletons are made up of cartilage instead of bones. Cartilage is the same stuff that makes your ears and the tip of your nose have their shape and be a little bit flexible. Even though they don't have bones, sharks do have lots of other similarities to bony fish. They are cold-blooded and breathe through gills instead of through lungs. Sharks have gills on each side of their heads. As they swim, water passes over the gills and oxygen flows in from the water.
Most kinds of whales live in groups called pods. The pods are kind of like families. The older whales take care of the younger whales, which are called calves. Whales stay together in their pods for most of their life. Most kinds of whales live somewhere in the middle of the ocean so that they can quickly get to the surface since they need to go up for air a lot.
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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