Most animals have a digestive system with a mouth for eating and an exit for getting rid of waste. Between the mouth and the exit is some kind of tube that digests and absorbs the food.
The animals in this section are so simple they don’t even have a digestive system that includes a mouth and a separate exit. Sponges, sea jellies and sea anemones are some of the no frills animals you can find living in rockpools.
Even though they have simple structures, the chemistry in their cells is just as complicated as our cells. There is still a lot we can learn about how these animals’ simple bodies work. By studying these sea creatures we will better understand our own bodies and how our cells work.