The lengthy small intestine receives secretions from the and , completes digestion of the nutrients in , absorbs the products of digestion, and transports the remaining residues to the intestine.

The lengthy small intestine receives secretions from the pancrease and liver, completes digestion of the nutrients in chyme, absorbs the products of digestion, and transports the remaining residues to the large intestine.

Explanation: digestion of food is necessary for absorption of nutrients. In this process food is broken down into forms that can be absorbed by the body . food is broken down by the teeth and the enzymes in saliva,when it is in the mouth. From there it moves to the stomach through the oesophagus. In the stomach, the content is further mixed with enzymes and the churning breaks down food further.From the stomach food moves to the small intestine. In the small intestine, digestive enzymes from the pancreas and liver acts on food. The small intestine is where digested food is absorbed.it has a large surface area and finger-like projection called villi to carry out the function of absorbing nutrients.

From there, undigested food us passed to the large intestine from where it is passed out through the anus

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.