What is the initial energy source used in photosynthesis?

The initial energy source used in photosynthesis is sunlight. During this process, green plants, algae, and some bacteria capture light energy from the sun through pigments such as chlorophyll. This light energy drives the chemical reactions that convert carbon dioxide and water into glucose and oxygen. The ability to harness sunlight is crucial for the survival of these organisms, as it enables them to produce their own food and, ultimately, provides energy for other organisms in the ecosystem.

Sunlight is essential because it provides the energy needed to split water molecules in a process called photolysis, releasing oxygen as a byproduct and generating energy-rich molecules like ATP and NADPH. These molecules are then used in the Calvin cycle to synthesize carbohydrates from carbon dioxide.