Vertebrates and InvertebratesThe living things in the world are divided into two big groups: plants and animals. Animals are classified into two smaller groups by examining their skeletons. Reach your hand behind you and run your fingers up and down the center of your back. That long, bumpy ridge you feel is the backbone, which is also called the spine. It is made of a stack of small bones, each one called a vertebra. Animals with backbone are called vertebrates. A horse, a dog, a cat, a fish, a bird, a frog etc are examples of vertebrates.
Many animals have backbones but many do not. An animal that does not have a backbone is called an invertebrate, a word that means no backbone. Earthworms, a moth, an oyster, a spider etc all are invertebrates.
The vertebrates are further classified into five smaller groups, fish, amphibians, reptiles, birds and mammals.
Cold-blooded and Warm-bloodedSome animals get the warmth they need from the air or water around them. When its hot outside their body temperature rises. When its cold, their body temperature drops. These animals are called cold-blooded animals. It doesn’t mean that blood is always cold. It means their body temperatures go up or down depending on the temperatures around them. Fish, amphibians, and reptiles are cold- blooded.
Other animals stay nearly the same temperature no matter whether the air around them is hot or cold. These animals are called warm-blooded animals. Mammals and birds are warm-blooded.
Directions: Answer the following questions.