The green plants have an autotrophic mode of nutrition.
An autotroph is an organism that can produce its own food using light, water, carbon dioxide, or other chemicals. Because autotrophs produce their own food, they are sometimes called producers.
Methods of procuring food or obtaining food by an organism are called modes of nutrition. Depending on the mode (or method) of obtaining food, all the organisms can be classified into two groups: autotrophic and heterotrophic.
There are mainly two modes of nutrition:
- Autotrophic
- Heterotrophic.
Autotrophic Mode of Nutrition: The word 'auto' means 'self' and 'trophe' means 'nutrition'. Thus, autotrophic means 'self nutrition'. Organisms, which utilize carbon dioxide as their sole source of carbon for the formation of organic food (like glucose, etc.) by the process of photosynthesis are called autotrophs. In addition to carbon dioxide, autotrophs require water and several inorganic ions. The green plants have an autotrophic mode of nutrition. Non–green plants are, however, not autotrophs. Certain bacteria called 'autotrophic bacteria' are also autotrophs.
Hetertrophs depend on autotrophs for their nutrition.
An organism that cannot synthesize its own food and is dependent on complex organic substances for nutrition.
Heterotrophic Mode of Nutrition: The word 'heteros' means 'others' and 'trophe' refers to 'nutrition'. Thus, 'heterotrophic' means 'nutrition obtained from others'. Organisms, which are incapable of photosynthesizing, obtain certain organic compounds from other autotrophs directly or indirectly and they are called heterotrophs and this type of nutrition is referred to as heterotrophic nutrition.
A heterotrophic organism (or heterotroph) can obtain its food from other organisms in three ways. So, the heterotrophic mode of nutrition is of four types:
- Parasites
- Saprophytes
- Insectivorous Plants
Parasites are organisms obtain food from other living organisms (the host), with the host receiving no benefit from the parasite. A saprophyte is an organism that obtains its nutrition from assimilating organic matter. Like the fungi, the saprophyte is a heterotroph, meaning that it does not make its own food. Insectivorous plants (Carnivorous plants) are said to be partly autotrophic and partly heterotrophic. These autotrophs supplement their nutritional requirements by trapping and digesting insects and other small animals.