(A) (i) Paramecium has cilia all over its body. As soon as it comes in contact with a food particle in the surroundings, the cilia start beating rhythmically in a specific direction, pushing the food towards the mouth opening.
(ii) (a) Hydrochloric acid: It softens the food and kills germs inside the stomach that may have entered with food. It activates the protein digesting enzymes in stomach by providing them acidic pH.
(b) Trypsin: It helps in activating all other enzymes of small intestine that help in digestion of various food components. It also helps in protein digestion.
(c) Muscular walls of stomach: They help in churning the food and passing them down through alimentary canal by their squeezing.
(d) Salivary amylase: It breaks down complex food sugars into simpler maltose in mouth. It also contains lysozymes to kill germs and softens the food and lubricates it for easy passage through alimentary canal.
OR
(B) (i) Blood goes through the heart twice during each cycle of purification. This is known as double circulation.
(ii) The separation of the right side and the left side of the heart is useful to keep oxygenated and deoxygenated blood from mixing. Such separation allows a highly efficient supply of oxygen to the body. This is useful in animals that have high energy needs, such as birds and mammals, which constantly use energy to maintain their body temperature. In animals that do not use energy for this purpose, the body temperature depends on the temperature in the environment. Such animals, like amphibians or many reptiles have three-chambered hearts, and tolerate some mixing of the oxygenated and de-oxygenated blood streams.