Jellyfish, or sea jellies, are free-swimming marine animals with a large bell-shaped top and tentacles trailing behind it. Jellyfish are only 5% structural proteins, nerves, and muscles and are 95% water! Jellyfish do not have brains or hearts!
They don’t have hearts because they do not have blood that needs to be pumped around their bodies. Jellyfish are very simple creatures that don’t need blood to survive. They don’t have a brain like humans or birds, but they do have a simple nervous system that senses temperature, touch, and many other things. That is why jellyfish don’t have brains or hearts! They don’t need them to survive because they are simple creatures.