Question

Which animal has no brain and heart?

Answer 1

Hint: Jellyfish are the oldest multicellular animal on the planet. Fossils of jellyfish have been discovered by scientists, which are more than $$500$$ million years old. So, they are even older than dinosaurs. But they don’t have a central nervous system. It is the biggest animal on the planet without a heart. But, it has the capacity to regenerate itself. But it is a primitive and very simple creature on earth.

Complete answer
Jellyfish do not have heart and lungs. In addition, it does not have a brain either. But jellyfish are able to live without those organs.
Jellyfish have very thin skin. Skin is helpful in absorbing oxygen through it. Thus, there is no need for lungs for respiration.
There is no blood present in the body of the jellyfish. So, there is no need for any heart-like organ to pump blood.
The outer layer of the skin is epidermis. Below the epidermis, there is a nerve present. The nerve sends signals from the environment. On receiving the signal, jellyfish respond to the changes occurring in the environment. The epidermis layer is so sensitive to touch. Hence, jellyfish are not in a position to need a brain for processing complex signals. They have a neural net in the body, which is a system of nerve cells.

Note:
Even jellyfish travelled into space. It multiplied too there. There is no answer from the scientists, how it deals with the gravity in space. The body content of jellyfish is $$85$$% - $$98$$% water. As the water evaporates, the jellyfishes almost disappear on the beach. Lion’s mane jellyfish is the largest jellyfish species in the world, which has tentacles $$27$$meters long. It is longer than the size of the blue whale.