Animals That Live in the Sea

These facts about ocean animals will help interest kids of any age about amazing sea animals. There are five main including the Pacific Ocean, Atlantic Ocean, Indian Ocean, Arctic Ocean and Southern Ocean. There are over 250,000 species of animals living in the world's oceans.

Types of Ocean Animals

Ocean animals are classified into 2 major categories. These categories include vertebrates and invertebrates. Invertebrates have a backbone, but invertebrates do not have a backbone.

There are six major classes of animals which are known as phylum. The six phyla include Cnidarians, Arthropods, Mollusks, Annelids (worms), Chordates, and Echinoderms. All six phyla include oceans animals.

All vertebrates are Chordates, which are animals with a doral nerve chord. Chordates include mammals, amphibians, reptiles, birds and fish.

Ocean Vertebrates

Vertebrates include some of the most known sea animals including fish, whales, sharks and dolphins. Although there are millions of vertebrates in the oceans, there are not nearly as many vertebrates as invertebrates.

Sea Mammal Facts

Sea mammals are an order under mammals. There are several orders of sea mammals including Sirenia (dugongs and manatees) and Cetacea (whales, porpoises and dolphins).

There are two suborders of Cetacea, toothed whales and baleen whales. Toothed whales have teeth and eat like most land mammals by chewing their food. Baleen whales have a large filter called a baleen. As they swim, they can catch large amounts of food to eat in their baleen.

Mammals are a diverse group of animals. Their size, shape, and location where they live varies widely.

There are over 4000 different types of mammals.

Mammals that live in the ocean are warm-blooded. Their body must generate heat to maintain a normal temperature.

Whales are the largest animals on Earth. Whales are mammals that live in the ocean. The Blue Whale can grow to a length of over 100 feet (30 meters).

All ocean mammals have hair, including the whales, manatees, dugongs and other mammals that live in the ocean.

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Reptile Facts

Although most reptiles live on dry land or spend time in freshwater, there are reptiles that live in the oceans.

The most well-known reptiles that live in the ocean are sea turtles. Sea turtles can live for many years and can grow very large. In the ocean, they are able to swim effortlessly and dive very deep to find food or escape danger

Sea snakes are another type of reptile that lives in the ocean

All reptiles are cold-blooded animals, including the ones that live in the ocean.

Reptiles must breathe air. Sea Turtles and other reptiles that spend their time in the ocean must come to the surface for air.

All reptiles have dry scaly skin.

All ocean reptiles are born from eggs.

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Ocean Amphibian Facts

Even though amphibians typically live near water or wet ground, there are no known species of amphibians that live in the open ocean. There are some amphibian species, however, that have been observed to tolerate brackish saltwater on the edge of the sea.

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Ocean Fish Facts

Ocean fish live in salt water during their entire life, although there are some exceptions. One exception is the rainbow trout, which is born in freshwater. Some rainbow trout travel to saltwater and live in the ocean. When they move to saltwater, they physically change and then are known as Steelhead. Steelhead return to freshwater to spawn, then the cycle starts over again. If the rainbow trout do not travel to the ocean, they remain rainbow trout.

Fish that live in the ocean breathe by using their gills, similar to freshwater fish, to extract oxygen from the water.

Most fish are cold-blooded, but two types of fish, the tuna family, mackerel and some sharks, are warm blooded or have a body temperature that changes independent of the surround water.

Scientists have identified more than 28,000 types of fish. Since these are many unexplored areas of water, scientists believe there are many more types of fish.

Invertebrate Facts

Invertebrates represent the largest number of animals in the ocean. There are 17 main groups of invertebrate identified by scientists which live in the sea.

There are five major groups, known as phylum, of invertebrate found in the ocean, including Cnidarians, Arthropods, Mollusca, Annelida and Echinoderms. There are many more classes of invertebrate below the major phylum. Some of these classes include Crustaceans, Sipuncula, Echiura, Nematoda, Nemertea, Platyhelminthes, Ctenophara, Hermichordata, Chaetognatha, Brachiopoda, Bryozoa, Phoronida, and Sponges.

Over 75 percent of the known animal species are Invertebrates.

Scientists think there could be millions of unknown ocean invertebrate species that have not been identified.

Arthropods, which includes the largest number of animals on Earth (over 1 million types), are a diverse group of animals which include insects. Ocean arthropods include crabs, prawns, horseshoe crabs and lobster. Arthropods are known for having an exoskeleton which is a hard protective outer surface on their body.

Cnidarians include a wide range of ocean animals. coral is a cnidarian. When this tiny creature dies its body becomes part of a large rock-like substance in the ocean. Jellyfish and sea anemone are also included in this group of invertebrates.