Modes of Nutrition

What is Nutrition?

Nutrition is the relationship between health, diet and disease. We intake food for the growth and development and receive energy in the form of nutritive food. This intake of nutrients that helps us to sustain and grow is called nutrition. This is the nutrition definition Biology can relate with. Broadly explained, it involves the Science where the study of nutrients and other food substances are studied to gain knowledge about the maintenance, growth, health, reproduction and disease of an organism. It also includes all processes taking place in the body like absorption, assimilation, food intake, catabolism, biosynthesis and excretion. Healthy nutrition is important for the body with the right and balanced nutrients present in the diet we consume. It will prevent diseases from occurring and maintain the right kind of lifestyle. Unhealthy nutrition is harmful physically as well as mentally, therefore, one should always seek the correct food in the right proportions and a variety of food that helps us heal all the time. A nutritionist gives a healthy nutrition plan and helps you maintain the right weight and calories goal. Knowing all of these, by now, you must have been aware of what is nutrition all about.


Not only human beings, but all living organisms including plants and microorganisms require nutrition to survive healthily. Therefore, nutrition in living organisms is equally important for all to obtain energy and derive nutrients for growth and development. There are various types of nutrition that an organism can engage in and we will know each of them further.  

Modes of Nutrition

The different modes of nutrition can answer the following question:

How Do Organisms Obtain Their Nutrition?

The below diagrammatic representation shows the different modes of nutrition in a precise manner which we will also describe ahead.

Depending upon the various modes of nutrition in living organisms, nutrition can be divided into the following categories:

  1. Autotrophic Nutrition

  2. Heterotrophic Nutrition

Autotrophic Nutrition

Nutrition in living organisms varies according to their way of food consumption. Autotrophic nutrition refers to that kind of nutrition when organisms are involved in making their own food. They can be classified into: 

  • Photoautotrophs- Organisms that make their own food by using sunlight as the source of energy are called photoautotrophs. Eg: Green plants, algae and photosynthetic bacteria.

  • Chemoautotrophs- Organisms that synthesise food with the oxidation of chemicals. Eg: Sulphur-oxidizing bacteria, cyanobacteria and iron-oxidising bacteria.

Certain Characteristics of These Kinds of Organisms Include:

  • They synthesise their own organic molecules from simple inorganic substances like carbon dioxide and water.

  • Organisms that synthesize their own organic molecules are referred to as producers. So, autotrophs are often termed as producers.

  • For example, plants synthesize their own food via photosynthesis in the presence of sunlight. During this process, the oxidation of inorganic compounds takes place to generate oxygen and energy in the form of glucose (sugar or carbohydrates). The biochemical reaction involved in photosynthesis is written as-

            6CO2 + 6H2O → C6H12O6 + 6O2

  • The photosynthetic process includes three stages namely absorption, conversion and reduction. 

  • During absorption, the chlorophyll pigment present in the plant leaves trap the sunlight.

  • During conversion, chemical energy is generated from the absorbed light  and water gets converted to hydrogen and oxygen molecules.

  • During reduction, hydrogen molecules combine with the carbon and reduce carbon dioxide to carbohydrates or sugar molecules. 

  • Plants or autotrophic organisms like algae, cyanobacteria, seaweed and phytoplankton depend on other micro and macro elements present in their environment to synthesise their own food. Green plants depend on soil to get various nutrients too which are used to produce proteins and other essential organic compounds. 

Heterotrophic Nutrition

Heterotrophic nutrition is one of the types of nutrition when organisms are unable to synthesise their own food and depend upon other organisms for deriving the nutrients. Certain characteristics of these organisms include-

  • These organisms obtain organic molecules or food from other organisms that can be living or recently killed or non-living remains and detritus.

  • Heterotrophs cannot produce their own organic molecules and therefore depend upon other sources of energy, thus they are termed as consumers. 

  • If you ask what is the mode of nutrition in human beings? Then here is the answer to the question. The examples of heterotrophs include human beings who depend upon plants and animals to derive their food.

  • Other examples include all herbivorous, carnivorous and omnivorous animals like tiger, leopard, lion, snake, dogs, cats, fungi, parasites, etc.


Heterotrophs can be further classified into the following:

  • Consumers where they ingest organic molecules from living or recently killed organisms. This category includes examples like parasitic leeches, ticks, humans, deers, lions, etc.

  • Heterotrophs who ingest organic molecules through non-living remnants of various organisms are the detrivores. Examples include hummus and detritus.

  • Saprotrophs that live on dead and decaying organic matter by releasing digestive enzymes to absorb the nutrients. These are often termed as decomposers. Examples include mycorrhizal fungi, orchids, mushrooms and molds.

FAQ (Frequently Asked Questions)

1. Why is nutrition important for a living organism?

Nutrition is important for a living organism because it provides nutrients that help break down food to provide energy for organisms. This energy is further utilized in the growth and development and carrying out various life processes like metabolism, catabolism, assimilation, reproduction, etc. Nutrition in humans will help in living a healthy lifestyle free of diseases and maintain the correct body mass index (BMI). A nutritionist will always suggest fitness enthusiasts with a list of diet charts that consists of different varieties of food to cover up all the nutrients for the body through proper nutrition.

2. Why do living organisms need nutrients?

Living organisms like plants, animals, human beings, and microorganisms need nutrients for the following reasons:


  • To obtain energy for their body processes.

  • For the proper growth and development and survive longer.

  • To fight against diseases and food deficiencies that may shorten their lives.

  • For repairing damaged cells and tissues and timely healing of their body.


3. What are the nutrients?

All the components of food substances necessary for the growth and development of all living organisms in the form of energy/sugar/carbohydrates/fats/proteins are called nutrients.