The system that circulates blood through the body, consisting of the heart and blood vessels. In all vertebrates and certain invertebrates, the circulatory system is completely contained within a network of vessels. In vertebrates, the lymphatic system is also considered part of the circulatory system.
While a squirrel isnât going to pen the next bestseller or ace a calculus class, the squirrel is smart in his own way. When looking at animal intelligence, humans shouldnât judge animals by human standards.
An order is made up of animals that have more features alike that those in a class. In the class Mammalia, all animals produce milk for their young. Cats, dogs, raccoons and shrew are all mammals. Dogs, cats and raccoons eat flesh are grouped together in an order called Carnivora with other flesh-eating animals. Shrews eat insects, and are classified in the order insectivora with other insect-eating animals.