How do jellyfish live without a brain?

Jellyfish survive without a brain by relying on a nerve net, a decentralized system of neurons that detects stimuli and controls movement. Instead of thinking, they respond automatically to light, touch, and chemicals in the water. Their pulsating motion is controlled by muscle-like cells, allowing them to swim efficiently. Some jellyfish even have simple eyes to detect light. Their survival depends on instinctive reactions, making them one of the simplest yet successful animals.