What Makes an Animal an Animal?
Five groups of life forms live on our planet, divided into what scientists call "kingdoms." They are: protists, bacteria, fungi, plants, and animals.
Animals share several important traits:
- they eat other living things
- they can usually move from place to place
- they react quickly to their environment
- their bodies have multiple cells
- they usually reproduce sexually.
That All-Important Backbone!
According to scientists, up to 99% of all animal species are Invertebrates, which means they lack a backbone. These include worms, jellies, anemones, snails, crabs, insects, and spiders.
Only 1% of all animal species are vertebrates (have a backbone). These are:
Animals are the most abundant living things on Earth. Scientists estimate there are about 9 or 10 million species. They exist in a staggering array of forms and sizes, ranging from a few cells to creatures that weigh several tons. Though most animals live in the seas, they're found in every habitat on the planet.
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