What is an invertebrate?
When most of us think about the diversity of life on earth, we think about the different kinds of birds in our backyard or the interesting animals we saw on our last trip to the zoo. What few of us realize, however, is that the overwhelming majority of life on earth is comprised of a type of animal known as an invertebrate.
Invertebrates are all around us, but we seldom notice most of them! As the figure below shows, there are nearly 1 MILLION kinds of invertebrates known to science, and only about 4,000 different kinds of mammals! Furthermore, some scientists believe that there may be more than 30,000,000 different kinds of invertebrates on earth, if only we had time to find and count them all!
So, what is an invertebrate? The category invertebrate does not comprise a single systematic grouping. The key characteristic of invertebrates is that they are animals without a bony backbone.
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