About Autotrophs

The organisms in an ecosystem that act as primary producers in a food chain are known as autotrophs. Their major source of energy is harnessed from sunlight through the photosynthesis process, because of this reason they are also known as photoautotrophs. Along with that they also obtain their energy through the oxidation process and because of that they are known to be chemoautotrophs. Through chemical processes, they make organic substances into an inorganic form. One of the major features of autotroph is that they do not consume other organisms as consumed by heterotrophs. In the word ‘autotrophs’, ‘auto’ means self and ‘troph’ means food i.e. they are the organism which feeds itself, without taking assistance of any other organism. 

Importance of Autotrophs

Autotrophs have their own specific importance in society, as without them no other life form can exist in society. Plants are the one which create sugar by taking carbon dioxide, gas and sunlight by the process called photosynthesis. Because of this reason, they are called producers. They form the base for the formation of higher ecosystems i.e. they act as a base for energy pyramids and also provide fuel to heterotrophs.  

From this, we can say that the first life on earth must be an autotroph. Heterotrophs are further evolved from autotrophs. 

Types of Autotrophs

On the basis of the process of obtaining energy, autotrophs are classified into two types, they are:

  1. Photoautotrophs

These are the organisms that obtain their energy from sunlight to make organic material. Examples of autotrophs are plants, green algae, and bacteria which perform photosynthesis. All of these photoautotrophs perform photosynthesis to make their food. In photosynthesis, the word photo means light and synthesis means to prepare or to make. In this process, organisms capture sunlight and use their energy to perform important biochemical processes such as making ATP. The amount of fuel or energy prepared by photoautotrophs is more than any other organisms like heterotrophs. 

Whereas some photoautotrophs take carbon from the atmosphere and use this carbon for preparing sugar and other molecules that store the Sun’s energy in their molecular bonds. 

  1. Chemoautotrophs

These are the organisms that obtain their energy from inorganic chemical processes. They are majorly found in deep water where the source of sunlight is almost negligible. For obtaining energy they use volatile chemicals such as molecular hydrogen, hydrogen sulfide, elemental sulfur, ferrous iron, and ammonia as their energy sources. 

Examples of Autotrophs

Some of the common examples of autotrophs are:

  1. Plants

  2. Algae- Green algae and red algae

  3. Bacteria such as cyanobacteria

  4. Lichens located in the tundra region are autotrophic in nature as they are considered to be primary producers as they undergo mutualism and combine photosynthesis by algae. 

Different Terms Related to Autotrophs

  1. Energy Pyramid – It is a structure that explains the flow of energy in different organisms. 

  2. Heterotroph – These are organisms that are dependent on another organism for food. Example: animals like Goat, Lion etc. 

  3. Photosynthesis – In this process phototrophs do the extraction of energy from sunlight.

Difference Between Autotrophs and Heterotrophs



Members of the plant kingdom and few unicellular species come under autotrophs. 

All members of the animal kingdom come under heterotrophs. 

They prepare their own food. 

They are dependent on other organisms for their food. 

They are classified into two types they are: 

photoautotrophs and chemoautotrophs.

They are also classified into two types, they are photoheterotrophs and chemoheterotrophs. 

Chloroplast plays a major role in preparing food.

The chloroplast is absent in them. 

They can store light energy and chemical energy.

They cannot store any source of energy. 

They occupy the primary position in the food chain. 

They occupy the secondary or tertiary position in the food chain. 

They are not movable. 

They can change their shelter. 

MCQ Questions

1. From the options below, which of the following is not an example of photoautotrophs?

A. Daisies

B. Iron bacteria

C. Cyanobacteria

D. None of the above.

Ans. Iron bacteria

2. Which of the following organisms first appeared on the earth surface?

A. A photoautotroph.

B. A chemoautotroph.

C. Neither of the above.

D. No one knows.

Ans. Neither of the above

FAQs (Frequently Asked Questions)

1. Name organisms that are both autotrophs and heterotrophs.

Cyanobacteria are organisms that are both autotrophs and heterotrophs as they show photoautotrophic nutrition. Another example of organisms that act as both autotrophs and heterotrophs is Archaea.

2. Explain the term photoheterotrophs and chemolithoheterotrophs.

Photoheterotrophs are organisms that obtain carbon from organic compounds but obtain energy from light, whereas chemolithoheterotrophs obtain carbon from organic compounds and energy from the oxidation of inorganic compounds.

3. Explain different types of autotrophs?

Autotrophs are classified into two types, they are:

Photoautotrophs:  They use sunlight to prepare their own food.

Chemoautotrophs: They obtain energy from carbon dioxide using inorganic energy sources.