What is the primary source of energy for most ecosystems?

The primary source of energy for most ecosystems is the sun. Sunlight is essential for photosynthesis, the process by which green plants, algae, and some bacteria convert light energy into chemical energy. During photosynthesis, these organisms use sunlight to transform carbon dioxide and water into glucose and oxygen. The glucose produced serves as an energy source for the plants themselves and for the organisms that consume them, including herbivores and subsequent levels of the food chain.

This solar energy ultimately drives the entire ecosystem, as it supports primary producers at the base of the food web. Those producers form the foundation of all food chains and food webs, linking different species and facilitating the flow of energy through the ecosystem.

In contrast, water and soil nutrients are important for the growth and health of organisms but are not energy sources in themselves. Wind can aid in pollination and seed dispersal, but it does not provide energy directly. Therefore, sunlight stands out as the most critical energy source sustaining life in ecosystems.