The primary energy source for most living organisms is sunlight, which drives the process of photosynthesis. In this process, plants, algae, and some bacteria harness solar energy to convert carbon dioxide and water into glucose, a form of chemical energy. This energy is essential for growth, reproduction, and metabolism. In turn, animals obtain energy by consuming plants or other animals, relying on the organic compounds created through photosynthesis. The energy transfer through the food chain illustrates the interconnectedness of ecosystems, where sunlight ultimately sustains life on Earth. Beyond photosynthesis, living organisms also extract energy from various chemical processes, including cellular respiration.