Animal Planet

Technorati Profile
Animals are a major group of organisms, classified as the kingdom Animalia or Metazoa. In general they are multi­cellular, capable of locomotion at some stage in their life cycle, responsive to their environment, and feed by consuming other organisms or parts of them. Their body plan becomes fixed as they develop, usually early on in their development as embryos, although some undergo a process of metamorphosis later on.

The word "animal" comes from the Latin word animal, of which animalia is the plural, and is derived from anima, meaning vital breath or soul. In everyday colloquial usage, the word usually refers to non-human animals. The biological definition of the word refers all members of the Kingdom Animalia. Therefore, when the word "animal" is used in a biological context, humans are included.

Animal classification.

Invertebrates

Animals without a Backbone or Spinal Column:

Of the million or more animal species in the world, more than 98% are invertebrates. Invertebrates don't have an internal skeleton made of bone. Many invertebrates have a fluid-filled, hydrostatic skeleton, like the jelly fish or worm. Others have a hard outer shell, like insects and crustaceans. There are many types of invertebrates. The most common invertebrates include the protozoa, annelids, echinoderms, mollusks and arthropods.


Crustaceans

Crustaceans are a type of Arthropod. The name may not sound familiar, but you probably know them. You may even have eaten one.

Crustaceans live mostly in the ocean or other waters. Most commonly known crustaceans are the crab, lobster and barnacle.

Crustaceans have a hard, external shell which protects their body. Crustaceans have a head and abdomen. The head has antennae which are part of their sensory system. The abdomen includes the heart, digestive system and reproductive system.

Protozoa

Protozoa are simple, single-celled animals. Most protozoa are microscopic in size.

There are several types of protozoa. The amoebas ar

e clear, shapeless cells. Flagellates have a body sh

ape looking like a hair.

Worms and Leeches

Annelids have bodies that are divided into segments. Annelids have very well-developed internal organs.

Some may have long bristles. Others have shorter bristles and seem smooth, like the earthworm shown here.

There are about 9,000 species of Annelids known tod

ay, including worms and leeches.

Vertebrates

Animals with a Backbone or Spinal Column:
(All these arnimals are in the phyla Chordata and the subphyla Vertebrata.)

Animals with an internal skeleton made of bone are called vertebrates. Vertebrates include: primates, such as humans and monkeys; amphibians; reptiles; birds; and, fish. Alt

hough vertebrates represent only a very small percentage of all animals, their size a

nd mobility often allow them to dominate their environment.

Fish

Almost three-forths of the world's surface is covered in water. This water is home to over 20,000 different species of fish. The earliest fossils of fish date back over 400 million years.

There are a wide variety of fish — from the goby which is less than one

half an inch long, to the whale shark which can be over 60 feet long.

Most fish breathe through gills. Gills perform the gas exchange between the water

and the fish's blood. They allow the fish to breathe oxygen in the water.

Fishes are vertebrates that have a skeleton made of either bone or cartilage. About 95% of fishes have skeletons made of bone. These bony fishes have a swim bladder, a gas-filled sac, that they can inflate or deflate allowing them to float in the water even when not swimming. Fishes with a cartilage skeleton tend to be heavier than water and sink. They must swim to keep afloat. Cartilaginous (cartilage) fish include the ray and the shark.

Amphibians

Amphibians lay their eggs in water, and young amphibians tend to resemble small fish.

The tadpole, or newborn frog, is born and lives in water. It has a tail that allows it to swim like a fish. It also has gills so that it can breathe under water. As the tadpole grow into a frog, it loses its gills and tail, and develops legs for moving on land. Most amphibians can both walk and swim in water.

Depending on the species of amphibian, breathing can take place in gills, lungs, the lining of the mouth, the skin, or some combination of these.

Amphibians body temperature changes with its environment. In cold climates, amphibians hibernate during the winter.

Reptiles

The most noticeable feature of reptiles are the scales that cover their body.

Although reptiles breathe through lungs, some reptiles can also absorb oxygen in water through membranes in their mouth.

Reptiles are often called cold-blooded because they can't regulate their own body temperature. Their body temperature depends on the external temperature.

Crocodiles and alligators are large amphibious reptiles. They can walk on land using their webbed feet. They can also use their long tail to swim in water. Crocodiles feed on large animals they catch on land or in water. They have powerful jaws and teeth to tear apart their prey.

Lizards and snakes are the largest group of reptiles. Lizards are four legged animals with a long tail. Many lizards can shed their tail to escape from predators. They can then grow a new tail.