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Do all animals have a brain?

Last Reviewed and Updated on June 10, 2022

Do all animals have a brain? And if they don’t, how do they live without one? These are all interesting questions and the answers will fascinate you.

Brains are the center of our being, we can not imagine a life without them. It turns out that not all animals have a brain. If they don’t have a brain, what do they have instead? Find out in this article, which looks at the brains of different species and what other organs take the place of their brain!

Do all animals have a brain?

The answer is no. Not all animals have a brain but most do. You won’t find an animal without a brain on land, but there are quite a few species that live without this fascinating organ in the sea.

Even insects, little creatures you might suspect would be without brains, in fact, have them.

We should note, for clarification purposes, that single-cell organisms aren’t classified as animals.

Which animals do not have a brain?

You might be surprised to learn that animals without a brain are quite common, even if there aren’t many species of them. Chances are you may have encountered them in your life.

Compared to animals with brains, these “no-brainers” lead a more simplified life, mostly with food, reproduction, and avoiding danger being the only things on their, well, mind.

Some of the animals without the brain include:

  • Jellyfish
  • Sea cucumbers
  • Sea Urchins
  • Anemones
  • Sea stars
  • Sea sponge
  • Sea lilies
  • Clams
  • Oysters

Now if you know anything about basic anatomy, you know with humans as well as most animals, the brain is what controls almost all bodily functions. Without a brain, there is no us… No thinking, no moving, no nothing.

Read facts about brains.

So how do these animals make it work? Well, it depends on the species.

Jellyfish for example is one of the more sophisticated animals without brains, as shown by their behavior and complex reproductive cycle. They have 2 nerve nets, one that helps them move and have the sense of where they are and one for everything else. They are aware of the position of their body parts and others (male/female).

Starfish have a nervous system spread throughout their tentacles and a nerve ring around the center which probably coordinates their behavior. They may also have a dominant arm, which coordinates the movement.

Many others on the list have similar, simple nervous systems that help them navigate life.

Sponges on the other hand have no brains, no nervous system, no neurons… Or even any other organs. At the moment, they are the only known multicellular organism without a nervous system or any kind of sensory cells. A true wonder of nature. They rely on filtering water through their body to get food and oxygen. Sponges don’t move. They are able to reproduce both sexually and asexually, which makes the fact they lack a brain or similar tissue even more fascinating.

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