My Science School

                 Mammals and birds are the main groups of warm-blooded animals. Some very active fish, such as tuna, are also warm-blooded. However, the mechanism that heats their bodies is different from that of mammals and  birds.

What is the advantage of being warm-blooded?

                    The chemical reactions that power the bodies of animals work best at warmer temperatures.

                   Warm-blooded animals are able to live and move about at any temperature that they experience in their normal environment. They can do this because their internal temperature is always the same. Cold-blooded animals, however, become sluggish as the temperature around them drops, and many will hibernate or migrate in very cold weather.

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                     Vertebrates have a backbone that provides support for the muscles and protection for the spinal cord. The backbone is actually a series of small bones called vertebrae. They are jointed together and locked with rope-like ligaments to provide a flexible but extremely strong anchor for the back muscles. The spinal cord runs down a channel inside the vertebrae, providing protection from damage. In some primitive fish, such as sharks and rays, the spine is made of a tough rubbery material called cartilage.

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                 The animal kingdom is divided into two groups — vertebrates and invertebrates. The vertebrate group contains all animals with backbones (as well as some that have a primitive form of backbone).Vertebrates include fish, amphibians, reptiles, birds and mammals. Invertebrates have no backbone. They include worms, molluscs, corals, scorpions, spiders, insects and crustaceans such as crabs and lobsters. Scientists divide these two main groups into smaller groupings that show the relationship between all these animals.

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                 Animals are one of the major groups of living things. The other two groups are plants and fungi.

                The cells of animals differ from plant cells because there is no hard cell wall. The cell contents are held together with a flexible membrane. Animals are not able to make their own food, but must obtain food from plants or fungi. Most animals are able to move about and to respond to changes in their environment.

About three-quarters of all living things are animals.

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