Which animal group besides Hydra also exhibits a diffused nervous...

A diffused nervous system, also known as a nerve net, is the simplest form of a nervous system found in multicellular organisms. It consists of interconnected neurons lacking a central brain or cephalization.

This type of nervous system is characteristic of radially symmetrical animals, primarily belonging to the phyla Cnidaria (such as Hydra, jellyfish, and sea anemones) and Ctenophora (comb jellies).

Mammals, birds, and insects possess a centralized nervous system with a distinct brain and nerve cords.

Answer: Ctenophora