Question

Discuss the major transformations in the digestive system of the vertebrates from the agnathan fishes to mammals.  Give one unique functional anatomical trait of the digestive system in Agnatha, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia. Try to relate this anatomical trait biology of each taxon. For example, why do birds (Aves) have a gizzard?

Answer 1

Birds have Gizzard,hind part of the stomach.It located between crop and the intestine.It is modified for grinding food because it contain small stones or gastroliths that function is the mechanical breakdown of seeds and other foods.

All animal like fish,amphibian,reptiles,Aves and mammals have closed digestive tract (mouth,oral cavity,pharynx,oesophagus,stomach,intestine and anus) and associated glands.