EVERYDAY SCIENCE

Detailed explanation-1: -Cnidarians, such as jellyfish, lack a true brain but have a system of separate but connected neurons called a nerve net. Echinoderms, such as sea stars, have neurons that are bundled into fibers called nerves.

Detailed explanation-2: -Abstract. Cnidarians have simple nervous systems and it was probably within this group or a closely-related ancestor that nervous systems first evolved.

Detailed explanation-3: -Sea anemones are cnidarians, like jellyfish and corals, and unlike most species that evolved later they don’t have discrete brains. Instead they have diffuse nets of nerves running through their bodies.

Detailed explanation-4: -The nerve net is the simplest form of a nervous system found in multicellular organisms. Unlike central nervous systems, where neurons are typically grouped together, neurons found in nerve nets are spread apart. This nervous system allows cnidarians to respond to physical contact.