What do spiders, clams, and grasshoppers all have in common? They are all invertebrates. So is the above organism, commonly known as a starfish. As you know, even though all of these organisms are invertebrates, they are very different from each other. They are in four different phyla.
You may know where a spider lives and you may even know some things about how it catches its prey. But where does a starfish live? Does it move? How does it reproduce? How does it eat? If a starfish is an invertebrate, how come it looks so different from other invertebrates? These are all questions that scientists ask when they are classifying an organism.
Scientists and naturalists now classify starfish in a phylum called Echinodermata, one of four phyla explored in this chapter.
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