INVERTEBRATES Animals without a backbone Invertebrates do not have an external skeleton made of bone. Others have a hard outer shell. The most common invertebrates include: Annelids * Anthropods * Echinoderms Mollusks * Protozoa Many invertebrates have a fluid-filled skeleton (jellyfish and worms), whilst others have hard outer shells. (insects and crustaceans). More than 98% of the animal species in the world are invertebrates. |
VERTEBRATES Animals with a backbone Invertebrates have an internal skeleton made of bone. Vertebrates include: Amphibians * Fish * Reptiles * Birds Mammals * Primates * Rodents Marsupials Most large land animals are vertebrates - even large sea animals. Although vertebrates represent only a small percentage of all animals, their size and mobility allow them to dominate their environment. |
WARM BLOODED ANIMALS Almost all mammals and birds are warm-blooded. They try to keep the inside of their bodies at a constant temperature. They do this by generating their own heat when they are in cooler environments, and by cooling themselves when they are in hotter environments. Warm- blooded animals require much more food to survive. |
COLD BLOODED ANIMALS Almost all insects, amphibians and arachnids are cold-blooded. These creatures take on the temperature of their surroundings. When the environment is hot, they are hot and vice-versa. They are also much more active in warm environments and very sluggish in cold environments. |