(a) Define nutrition. Why is nutrition necessary for an organism?
(b) What are the different modes of nutrition? Explain with one example of each mode of nutrition.
(c) Name the mode of nutrition in (i) roundworm, and (ii) Plasmodium.

(a) The process of intake of nutrients (like carbohydrates, fats, proteins, minerals, vitamins, and water) by an organism as well as the utilization of these nutrients by the organism is called Nutrition. It is necessary for an organism as it provides energy to them from the food they eat. 

(b) There are mainly two modes of nutrition. They are:

(i) Autotrophic Mode of Nutrition- In this mode of nutrition organisms make their own food from simple inorganic materials like carbon dioxide and water present in the surroundings (with the help of sunlight energy).

Example: Green plants obtain their food by autotrophic nutrition.

(ii) Heterotrophic Mode of Nutrition - In this mode of nutrition in which an organism cannot make its own food from simple inorganic materials like carbon dioxide and water, and depends on other organisms for its food.

Example: All animals obtain food by heterotrophic nutrition.

(c) The mode of nutrition in (i) roundworm and (ii) plasmodium is the parasitic mode of nutrition.  These are the organisms which feed on other living organisms called host for their nutrition.