Autotrophic nutrition refers to the process by which organisms produce their own organic molecules and energy sources using inorganic substances. There are different types of autotrophic nutrition found in the natural world. Here are four major types:

1. Photosynthesis: This is the most common type of autotrophic nutrition and is primarily found in plants, algae, and some bacteria. Photosynthetic organisms use sunlight, carbon dioxide, and water to produce glucose (a simple sugar) and oxygen. The process occurs in specialized organelles called chloroplasts, where pigments like chlorophyll capture sunlight energy and convert it into chemical energy.
2. Chemosynthesis: Unlike photosynthesis, chemosynthesis does not rely on sunlight as the energy source. Instead, certain bacteria and archaea utilize the energy from inorganic chemical reactions, such as oxidation of sulfur or methane, to produce organic molecules. These organisms are typically found in extreme environments such as deep-sea hydrothermal vents or sulfur-rich caves.
3. Lithotrophy: Lithotrophs are organisms that obtain energy from inorganic compounds (minerals) and use it to synthesize organic molecules. These organisms can be found in diverse habitats such as soil, rock surfaces, and deep-sea environments. They are capable of oxidizing minerals like iron, sulfur, or ammonia to generate energy.
4. Acetogenesis: Acetogens are a group of bacteria that produce acetate (a type of organic acid) as a metabolic end product. They use carbon dioxide as their carbon source and generate energy by various chemical reactions. Acetogens are found in environments such as anaerobic sediments, wastewater treatment plants, and the gut of animals.

These are just a few examples of autotrophic nutrition in the natural world. Each type of autotrophy has its own specific mechanisms and adaptations to harness energy and synthesize organic compounds without relying on external food sources.