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A. The process of taking nutrients from organisms or preparing the food on their own in order to get energy to do work is known as nutrition. Carbohydrates, proteins, fats, minerals and vitamins are important nutrients present in food.

B. In heterotrophic mode of nutrition organisms obtain their food from other organisms. There are 3 types of heterotrophic nutrition:

i. Saprophytic nutrition: - In saprophytic mode of nutrition organisms feed on dead and decaying matters to obtain their nutrition. They absorb their nutrition through their body wall. E.g. bacteria and fungi.

ii. Parasitic nutrition: - In parasitic mode of nutrition one organism depends on the other organism often known as host, to get their nutrition. In this host body is not benefited but is harmed by the parasitic organism. Example plants like cuscuta and animals like tapeworm, ascaris etc.

iii. Holozoic nutrition: - In this type of nutrition parts of organism takes in food which is then digested by different digestive enzymes by converting complex substances into simpler form. And then undigested food is thrown out of the body. Example amoeba.