Here's why:
* Photosynthesis: Plants and other photosynthetic organisms use sunlight to convert carbon dioxide and water into glucose (sugar) and oxygen. This process is called photosynthesis, and it's the primary way energy enters the ecosystem.
* Food Chain: Plants are eaten by herbivores, who are then eaten by carnivores. The energy stored in the glucose produced by photosynthesis is passed along the food chain.
* Cellular Respiration: All living things, including plants and animals, use the energy stored in glucose through a process called cellular respiration. This process releases the energy needed for growth, movement, reproduction, and other essential functions.
So, while living things use energy in different ways, it all originates from the sun through the process of photosynthesis.
