In which animal nerve cell is present but brain is absent = 1- Sponge 2- Eartworm
3- Cockroach 4- Hydra ? And why ??

Dear Student

Correct answer is (4)

Hydra has nerve cells but no brain. 

It belongs to the phylum Coelenterata. Its nervous system consists of nerve cells and their processes. Sensory cells are also present but the brain is absent.

Sponges lack the nervous system and they do not have nerve cells.

Earthworm and cockroach have a nervous system consisting of a circumcenter nerve ring and a solid, double, midventral nerve cord with ganglia.


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