About three quarters of the earth is covered by sea. Oceans are divided into numerous regions depending on the physical and biological conditions of these areas. The area of the World Ocean is 361 million square kilometers. In shallow parts of the sea the light reaches all the way to the bottom while in the deep sea, the light only reaches the top part of the sea. In the sea there is zooplankton (tiny fish) and phytoplankton (tiny sea grass). These are the food that the fish eat.
Many types of fish live in the sea. Some birds live near the sea and eat fish and there are also some mammals that live in the sea.
Dolphins are mammals that are completely adapted to live in the water and never leave it. Dolphins live in tropical, subtropical and warm seas all over the world. Sometimes they come at the water` s surface to breathe .Their body is hydrodynamic in shape, the front legs have been changed into flippers and at end of the body there is a caudal fin. They swim and dive excellently , and feed on fish and cephalopods .The common dolphin is a social species. They gather in large schools that live in the open sea. They swim fast, and also perform different acrobatics. Dolphins have one child each and they teach and discipline their child. Dolphins communicate by using different sounds.
Elenia
Whales are large, aquatic mammals. They breathe air through blowhole(s) into lungs (unlike fish who breathe using gills). Whales have sleek, streamlined bodies that move easily through the water. They are the only mammals, other than manatees, that live their entire lives in the water, and the only mammals that have adapted to life in the open oceans
Like all mammals:
- Whales breathe air into lungs,
- Whales have hair (although they have a lot less than land mammals, and have almost none as adults),
- Whales are warm-blooded (they maintain a high body temperature),
- Whales have mammary glands with which they nourish their young,
- Whales have a four-chambered heart.
The biggest whale is the blue whale, which grows to be about 94 feet (29 m) long - the height of a 9-story building. These enormous animals eat about 4 tons of tiny krill each day. Adult blue whales have no predators except man.
Luke Farrugia
Starfish
Starfishes are the typical inhabitants of the sea bottom in shallow areas. The orange starfish especially likes sandy bottoms. Its body is flat, and there are five arms extending from the central part of it. In the middle of its body, on the bottom side, there is a mouth opening, and on the upper there is a small screen plate through which the water comes in. On the arms there are tube feet, which are used for moving along the sea floors. The orange starfish are carnivores, and they mostly feed on shells and snails. The orange starfish lives in the Mediterranean Sea. If the prey is small, they swallow it at once, and if it is bigger, they avert their stomach through their mouth and digest the prey outside the body. For separating the shells of molluscs they also use the tube feet on their arms. Individual starfish are male or female. From the fertilised eggs, larvae come on the ground and transform into adult starfish.
The sea horse lives in the sea. The sea horse is unlike large and fast offshore fish. The seahorse manages to cross only 4 mm a second.
On the ventral side of male’s body there is a brood pouch into which a female inserts her eggs with a special organ. The male fertilises them and carries them in his brood pouch for 2 or 3 weeks. After hatching, the parents do not take care of the young anymore.
Dana Gauci
