I. Mouth: Involved in the ingestion of food, mechanical digestion (chewing), and the start of chemical digestion through saliva.

Here are the roles of the specified sections of the alimentary canal:

a)
i. Mouth: Involved in the ingestion of food, mechanical digestion (chewing), and the start of chemical digestion through saliva.
ii. Oesophagus: Transports food from the pharynx to the stomach via peristalsis.
iii. Ileum: Primarily responsible for the absorption of nutrients, especially vitamin B12 and bile salts, into the bloodstream.
iv. Large intestine: Absorbs water and electrolytes from indigestible food matter, forming feces for elimination.
v. Rectum: Serves as a temporary storage site for feces before defecation.
vi. Anus: The external opening through which feces are eliminated from the body during defecation.