The Wild Side

In order to be considered an animal, an organism must:

• be multi-cellular (have more than one cell in its body)

• be heterotrophic (an animal has to eat something to get its energy)

• have cells that form tissues, such as muscle, skin, and nervous tissue . . . An exception is sponges and corals! Did you know that sponges and corals are actually living animals?

How Do We Tell Animals Apart?

 

Scientists keep track of millions of living organisms by categorizing them into groups according to a universal classification system. This is called taxonomy. Every single species is organized into a domain, kingdom, phylum, class, order, family, and genus. Then the species is given its very own name (called its scientific name).

 

In the past, all living things were sorted into categories based on how they looked. However, we’ve learned that looks can be very deceiving, so today we organize animals, plants, bacteria, fungi, etc by comparing their genetics and evolutionary history.

 

Let’s use a common animal, a fox squirrel, to see how taxonomy works. Because squirrels have cells with a nucleus, they are classified into a domain group known as Eukarya (living organisms with different characteristics are classified in a different domain group). Because squirrels are animals, they are classified as being in the kingdom Animalia. Following this pattern of organization, the fox squirrel is classified into smaller and smaller groups of organisms until it’s the only one left, giving the species its scientific name!