Simple Animals

Most biology chapters start the animal kingdom with one called “Simple Animals”. This is quite misleading as there really is no such thing as a “simple” organism, or at best, “simplicity” is in the eye of the beholder. The dragonfly textbook has a chapter that includes an introduction to animals, and then a section on sponges, and a section on cnidarians (formerly known as coelenterates).

Many students won’t find either of these animals particularly fun and exciting. You can however, make things a little bit more interesting by including a lab component or at least have specimens on hand for students to play with. When we talk about sponges, I pass around an organic sponge for students to compare to a store-bought (synthetic) sponge. (You can order the organic sponge from biology supply companies or even pick some up from bath and beauty stores.) As they play with the two sponges, ask them to make a judgment about which one can absorb more water, ask them to compare they way they look.

I also have several specimen jars that contain jellyfish and the portuguese man of war. For some reason, the air bubble in that hydrozoan fascinates students. They always want to know what would happen if they popped it. Finally, students are allowed to view the hydra under the microscope. This small organism is visible with the naked eye, but more details can be seen even at low power – like the cnidocytes on the tentacles. See hydra lab for a printable for students to complete. I was able to capture a hydra doing a cartwheel on my slide – watch this amazing video!