Autotrophic nutrition is a mode of nutrition in which organisms synthesize their own organic compounds using inorganic substances as sources of energy and raw materials. These organisms are called autotrophs or self-feeders. Autotrophs are capable of converting simple inorganic compounds, such as carbon dioxide and water, into complex organic molecules, like glucose, through the process of photosynthesis or chemosynthesis.

1. Photosynthesis: The most common form of autotrophic nutrition is photosynthesis, which occurs in plants, algae, and some bacteria. During photosynthesis, organisms use sunlight as an energy source to convert carbon dioxide and water into glucose and oxygen. This process takes place in specialized structures called chloroplasts, which contain the pigment chlorophyll.

The equation for photosynthesis is:
6CO2 + 6H2O + sunlight energy → C6H12O6 (glucose) + 6O2

2. Chemosynthesis: Some autotrophic bacteria and archaea are capable of performing chemosynthesis. Instead of using sunlight as an energy source, these organisms derive energy from the oxidation of inorganic compounds, such as hydrogen sulfide or ammonia. Chemosynthetic organisms are found in environments such as deep-sea hydrothermal vents and certain soil ecosystems.

The equation for chemosynthesis can vary depending on the specific compounds used, but a simplified example is:
CO2 + 4H2S + energy → CH2O (glucose) + 4S + 3H2O

Autotrophic nutrition is essential for sustaining life on Earth, as it forms the basis of the food chain. Autotrophs, such as plants, are primary producers that produce organic matter, which is then consumed by heterotrophs (organisms that cannot produce their own food) such as animals. Through this process, energy and nutrients flow through different trophic levels in an ecosystem.

Autotrophs play a critical role in maintaining the balance of atmospheric gases, particularly by absorbing carbon dioxide and releasing oxygen during photosynthesis. They also serve as a source of food and energy for other organisms in the ecosystem.