Part one of term paper
The digestive systems works on nutrients taken from the environment, breaking them down into simpler products, and then absorbing the products together with water and salts so they can be used in metabolism. The individuals of all species contain many different protiens or carbohydrates in the cell walls of bacteria, chitin in the external s ...

Part two of term paper
... cell. Intracelular digestion is also found in some higher animals such as mussels and sponges. Muscles, for instance, filter algae and other tiny organisms from the water and digest them within the cells of a special digestive gland. Intracellular digestion occurs even in some animals that consume large pieces of food; the prey captured by Hydra, for example, is partly digested in the coelenteron, a gut-like cavity, and the residue is completely digested in cells of the body wall. Scientists believ ...