Correct option is A
- Autotrophs are organisms that produce their own food using light (in the case of photoautotrophs) or chemical energy (in the case of chemoautotrophs).
- They achieve this by fixing carbon dioxide (CO₂) during processes such as photosynthesis or chemosynthesis.
- In photosynthesis, autotrophs (like plants, algae, and cyanobacteria) use sunlight to convert carbon dioxide and water into glucose and oxygen.
- In chemosynthesis, certain bacteria use inorganic compounds (like hydrogen sulfide) to fix CO₂ into organic compounds.
Additional Information:
- Carbon fixation is a crucial step in the Calvin cycle, where CO₂ is incorporated into organic molecules.
- Autotrophs form the base of almost every ecological pyramid, providing energy and organic material for heterotrophs (organisms that cannot produce their own food).
Other Options:
- Carbon monoxide (CO): It is a toxic gas that is not directly fixed by autotrophs in significant biological processes.
- Methane (CH₄): Methane is a product of certain anaerobic processes, not a substrate fixed by autotrophs.
- Oxygen (O₂): Oxygen is a by-product of photosynthesis and not fixed by autotrophs
