Solution

Frogs do not have external ears. Instead, they have an eardrum of sorts, called a tympanum, which is just behind each eye. Typhlosole are internal folds of the intestine or intestinal inner wall. Typhlosole occurs in bivalve mollusks, lampreys and some annelids and echinoderms. The gizzard, also referred to as the ventriculus, gastric mill, and gigerium, is an organ found in the digestive tract of some animals, including birds, reptiles, earthworms and some fish. This specialized organ constructed of thick, muscular walls is used for grinding up food; often rocks are instrumental in this process. In certain insects and mollusks, the gizzard features chitinous plates or teeth. Humans have 12 pairs of cranial nerves. Cockroach belongs to class insecta of phylum arthropoda.