How do organisms that lack a brain know how to find food or avoid danger?

Question

Single celled organisms, jelly fish, etc.....no brain, yet they acquire food and move in response to stimuli.....how??

Answer 1

Jelly fish, sea anemones, basically all animals in the phylum Cnidaria don't have a brain but they have a cluster of nerve cells (ganglia), and they have statocysts (a balancing organ), ocelli (light-sensing eye) and chemical receptors which can detect chemicals given off by a prey/enemy.

In the end, they basically just hope that something runs into them. Like sea anemones, they don't really move so they just wave their tentacles around hoping that they'll catch something, and they sting anything that touches them, regardless of whether they choose to or not. Then they pull it into their mouth with their tentacles. Jellyfish is kind of the same thing but they have a greater range of movement.

Answer 2

OR it ought to be the thought that we are being taken on a experience, at our cost (a touch vast cost) for what? A small earnings? Is China or India going to diminish their carbon emissions? properly? So we wreck our economic device for what? Jeez Dana, in line with danger you are able to desire to have taken some economics instructions on an identical time as you have been in college. you will have found out something functional and been a earnings to society. Oh properly.

Answer 3

they still have nervous system or some way of responding to stimuli (light, smell etc.) For single-cell organisms it is probably more chemical than neural.

Answer 4

A Nervous system dosent allways need a brain to function some olny have Clusters of nerves

Answer 5

For bacteria they use quorum sensing. Wikipedia has a pretty good description.