body covered with moist skin which is devoid of scales, the ear is represented by a tympanum, alimentary canal, urinary and reproductive tracts open into a common cloaca

fresh water animals with bony endoskeleton, air-bladder to regulate buoyancy

marine animals with cartilaginous endoskeleton, body covered with placoid scales

body covered with dry and cornified skin, scales over the body are epidermal, they do not have external ears.

Cnidaria

Porifera

Protozoa

Ctenophora

House fly, butterfly, tse tse fly, silverfish-Insecta

Spiny anteater, sea urchin, sea cucumber - Echinodermata

Flying fish, cuttlefish, silverfish-Pisces

Centipede, millipede, spider, scorpion-Insecta