How do jellyfish survive without brains?

Jellyfish do not have a brain, heart, or blood and They are made up of mostly water, 95% to be exact. The jellyfish depends on their nerve ‘net.', which helps them to detect danger and find food. They can survive without a heart because they are supported by homeostasis and metabolism.

They do not need a brain or central nervous system because of how simple they are as creatures. They can draw in prey automatically from their stingers without the presence of a brain. They have very simple bodies which take in the nutrients.