ื animals
animals can be classified according to the backbone. Animals that have a backbone are called vertebrates. Animals that do not have a backbone are called invertebrates.
invertebrates can be sub-divided into three groups according to their physical characteristics. the first group has soft bodies with no bones at all, like worms. another group has soft body with a hard shell and can live in water or on land are grouped as mollusks. examples of mollusks are snails, clams, mussels, and squid. some other invertebrates have tough coatings on the outside of their bodies, jointed legs, and a segmented body. this group is known as the arthropods. insects, spiders, millipedes, and shrimp, and crabs are examples of arthropods.
All vertebrates have a backbone . they can be further classified as cold -blooded vertebrate or warm-blooded on the basis of their body temperature. the cold- blooded vertebrate changes its body temperature to the outside temperature.Fish,amphibians and reptiles are examples of clod-blooded animals.