Sponges and cnidarians are two of the animal phyla that lack bilateral symmetry. Sponges are considered the simplest animals with the lowest degree of cellular specialization. Cnidarians have two true tissue layers that form during embryonic development, while...
efferent,Referring to nerves that carry impulses away from the brain to glands or muscles; motor nerves. electrocardiograph,A machine used to make a recording of electrical waves from the heart; used in diagnosis of heart conditions. element,A substance that cannot be further simplified by chemical...