Types of Nutrition

 

Types of Nutrition

Broadly, there are two types of nutrition among living organisms, namely:

• Autotrophic Nutrition 
• Heterotrophic Nutrition 

Autotrophic Nutrition

Some organism is capable of preparing food on its own. Such organisms use simple inorganic matters like water and carbon dioxide in the presence of light and chlorophyll to synthesize food on their own. In other words, the process of photosynthesis is used to convert light energy into food such as glucose. Such organisms are called autotrophs. Plants, algae, and bacteria (cyanobacteria) are some examples where autotrophic nutrition is observed.

During photosynthesis, carbon dioxide and water get converted into carbohydrates. These carbohydrates are stored in the form of starch in plants. Plants later derive the energy required from the stored starch. The process of photosynthesis can be explained in three stages:

1. Absorption: The chlorophyll present in leaves traps the light coming from the sun.
2. Conversion: The absorbed light energy gets converted into chemical energy. And water absorbed will split into hydrogen and oxygen molecules.
3. Reduction: At last, carbon dioxide gets reduced i.e. hydrogen molecules combine with carbon, to form carbohydrates (sugar molecules).

Autotrophic Nutrition

All three events are not a continuous process. They may or may not take place sequentially.

In plants, stomata are the openings on leaves where gaseous exchange takes place and is regulated by guard cells. Plants take in and release gases through these stomatal pores.

In desert-like habitats, to avoid water loss, guard cells keep these pores closed during the daytime. Later, during the night time, stomata will be opened to absorb carbon dioxide and store in the vacuoles. During the daytime, they will use this stored carbon dioxide to perform photosynthesis.

Other than photosynthesis, plants also depend on soil for micro and macro elements. These elements are used to synthesize proteins and other essential compounds required for the proper functioning and growth of the plants.

Heterotrophic Nutrition

Every organism is not capable of preparing food on its own. Such organisms depend on others for their nutrition. The organisms which cannot produce food on their own and depend on other sources/organisms are called heterotrophs. This mode of nutrition is known as heterotrophic nutrition.

Fungi and all the animals including humans are heterotrophs. Heterotrophs can be of many varieties depending upon their environment and adaptations. Some may eat plants (herbivores) and others eat animals (carnivores) while few eat both (omnivores). Thus we can say survival of heterotrophs depends directly or indirectly on plants.

Heterotrophs are classified into different categories based on their mode of nutrition. They are:

• Parasites (e.g. leeches, ticks)
• Saprophytes (e.g. mushrooms)
• Holozoic (e.g. humans, dogs)