Posted by: Karen Fowler
Oceans cover more than 70% of the surface of the Earth and contain about 97% of Earth's water. They are also home to more than 230,000 known species, however, much of the ocean is unexplored and therefore is likely home to many more species that we don't yet know about. It is estimated that more than two million species actually exist in the world's oceans. Oceans are home to many species of fish, reptiles, mammals, and more. Continue reading to learn about some common animals that call the sea home.
Sea Turtles
Sea turtles are members of the reptile family and can be found in all the world's oceans with the exception of the Arctic. There are only seven living sea turtle species, and many of them are endangered. The seven types of sea turtles are the leatherback, loggerhead, green sea turtle, flatback, hawksbill, Kemp's ridley, and the olive ridley sea turtle. Each of these types, except the leatherback, have a hard shell. Leatherback turtles actually have a layer of bony plates underneath a leathery feeling skin. Leatherbacks are also the largest type of sea turtles and can grow as large as 7 feet. All other species of sea turtle are smaller, normally ranging from 2 to 4 feet. Sea turtles must surface for air but can stay underwater for long periods of time as they have developed something called anaerobic metabolism. Their large lungs are also built to avoid trapping gases during deep dives. Most sea turtles are omnivorous; only the green sea turtle is an herbivore. The diet of a sea turtle consists of a wide range of plants and animals.
Dolphins
Dolphins are highly intelligent marine mammals of which there are nearly 40 different species. They can be found all over the world, mainly in the shallower water of the continental shelves. All species of dolphin are carnivores, and feed mostly on squid and different fish. Dolphins range in size from approximately 4 feet and 90 pounds, to 30 feet and more than 9 tons. Killer whales, or orcas, are part of the dolphin family. Dolphins are considered social animals and live in pods that normally consist of up to one dozen animals. They have a highly developed system of communication, making whistle like sounds, clicks, and other noises. Scientists have found that dolphins call each other with distinctive whistles, and each dolphin in the pod will only respond to their unique whistle.
Whales
Whales are marine mammals, of which there are many different species. They can be found in all the world's oceans and number in the millions. Different species of whales range in size from 11 feet to 98 feet. The blue whale is the biggest animal known to have ever existed. While there are toothed whales, most whale species are considered filter feeders. This means that they eat small organisms that they catch by straining ocean water through their baleen. Baleen are sort of like combs and are located in a whale's mouth. All whales have blowholes on the top of their heads and they are used to breathe. This allows the whale to remain almost completely submerged in the water while breathing. Breathing consists of expelling water from the blowhole, and then inhaling air into the lungs.
Sharks
Sharks are a well-known type of fish with more than 470 different species. Sharks are characterized by their gill slits located on the side of the head, a skeleton made of cartilage, and pectoral fins which are not fused to the head. Sharks species vary widely in size with some being only a few inches while others are more than 30 feet long. These fish can be found in all the world's oceans and can be found in water more than 6,000 feet deep as well as shallow water. Sharks breathe through their gill slits, and have several rows of teeth. Some of the well-known shark species include the great white, the tiger shark, and the hammerhead shark.
Other Fish
The ocean is home to thousands of different species of fish. Fish are cold blooded and breathe through gills; they vary greatly in size, shape, and color depending on the species. Tropical fish that live in shallower waters tend to be brightly colored, while fish that live deeper in the ocean tend to be darker as this helps them to camouflage. The term "fish" includes species such as sharks, rays, and lungfish. While many different types of marine animals are referred to as fish, animals such as shellfish and starfish are not actually members of the fish family.
Octopus/Squid
Octopi (the plural of octopus) and squid are both considered cephalopods. Octopi have eight tentacles, and two eyes. They also have a hard beak, and their mouth is at the center point of their arms, or tentacles. Neither octopi nor squid have a skeleton. Octopi are very intelligent animals that live in many different regions of the ocean. They protect themselves by expelling ink, using camouflage, and moving very quickly through the water. All octopus species are venomous but the only species considered deadly to humans is the blue ringed octopus. Just like octopi, squid have 8 arms, or tentacles, however they usually have two longer tentacles as well. Squid are fast, strong swimmers, and there are more than 300 different species. Squid have the ability to camouflage by changing colors. This is due to their skin being covered in chromatophores, special parts of the squids' cells that allow them to change color.
Stingrays
Stingrays are a type of fish that are related to sharks. They range in size from very small to quite large. They can be identified by their flat bodies and barbed stingers on their tails that are used for self-defense. The barbed stingers can grow as long as 14 inches, depending on the species, and the underside has venom glands running along two grooves. The barbed stinger is covered in a thin layer of skin, where the venom is concentrated. Stingrays are most commonly found in tropical waters around the world. There are a few species, such as manta rays, and porcupine rays, that do not have stingers. Stingrays are excellent at camouflage and will conceal themselves beneath the sand. Their eyes are located on the top of their bodies and their mouths are on the underside.
Walruses
Walruses are large mammals that live in subarctic seas. They are easily identified by their long white tusks, big whiskers, and their large size. They can grow to more than 3,000 pounds. Walruses normally live in shallower water and spend a large amount of time on sea ice looking for mollusks to eat. Just like dolphins, walruses are social animals. Walruses are long lived animals and are covered in a thick layer of blubber to keep them warm in the freezing cold environment they call home.