How Do Living Things Get Their Food?
There are two methods of obtaining food, autotrophic and heterotrophic. In autotrophic nutrition, the organisms obtain inorganic raw materials (carbon dioxide, water, minerals) from the environment, pick up energy from solar radiations and synthesise organic food.
The organisms performing autotrophic nutrition are called autotrophs.
They include green plants, cyanobacteria, some bacteria and some protists. In heterotrophic nutrition, the organisms obtain readymade food from outside. This food is made of complex substances. They are first broken down into simpler ones by means of enzymes.
The simpler substances are picked up by living cells to build up their protoplasm and energy molecules. Organisms performing heterotrophic nutrition are called heterotrophs. They include animals, fungi, protozoans and many bacteria.