Flexi Says: Some simple invertebrate animals do not have brains. However, they still have ways to sense and interact with their environments. For example, although jellyfish do not have centralized brains, they have networks of neurons that detect and send information. Corals have similar neural nets. Sea stars and other echinoderms also lack centralized brains, but have fairly complex nervous systems nonetheless. They have senses to detect touch, light, temperature, orientation and chemicals in the water. Sponges are among the simplest animals. They lack any real nervous system. They live simple lives without active motion, and feed passively by filtering the ocean water that passes through their bodies.
