A jellyfish is an invertebrate animal with a body that is mostly water and gelatinous material. Jellyfish are not vertebrates, meaning they do not have a backbone. They have no heart, but they still need oxygen to survive.
Jellyfish have no heart because their bodies are mostly water and gelatinous material. Their bodies are made up of cells that can move independently of each other in order to avoid predators, which is why they don’t need a heart with blood vessels. .An invertebrate is an animal without a backbone. Examples of invertebrates are insects, worms and jellyfish. They do not have a heart because their bodies are mostly water and gelatinous material. Their bodies are made up of cells that can move independently of each other in order to avoid predators, which is why they don’t need a heart with blood vessels.