What physical feature pertaining to the organism and its medium do you notice in a sponge body form which sponges can be/were identified as animals and not plants ? What do you call the region in the sponge body in which you noticed that feature ?

Explanation

Sponges are primitive multicellular and sessile animals and have cellular level of organisation. The body wall is composed of two-layers separated by matrix mosohyl, and are heaving canal system for transport of water through Ostia, having a cavity in the body called a spongocoel hence the sponge are animals and are not plants.