The above image shows an organism from the phylum Cnidaria. What does that mean? Good question.
You may call the above organism a jellyfish. But a jellyfish is not a fish at all, although it is a part of the animal kingdom. Kingdoms are divided up into phyla, and this organism is classified in the phylum called Cnidaria.
How is the above organism different from you? What is its body shape? Does it have a brain? Does it have a way to digest food? Can it eat like us? Can it breathe? These are the types of questions scientists ask when they classify organisms, or put them into categories.
This chapter will explore how different invertebrates, organisms without a backbone, are classified into different categories. After reading this chapter, see if you can do a better job asking the right questions to put organisms into specific categories.
Flickr:The Pug Father. www.flickr.com/photos/fleur-design/2751750883/. CC BY 2.0.