Organisms obtain energy through various methods, primarily through the processes of photosynthesis and cellular respiration. Plants, algae, and some bacteria convert sunlight into chemical energy via photosynthesis. This process takes place in the chloroplasts, where light energy is transformed into glucose and oxygen. The glucose acts as a fuel source for the plant.
On the other hand, animals and many fungi and bacteria obtain energy by consuming plants or other organisms. Through a process called cellular respiration, they break down glucose (derived from food) to release stored energy. This occurs in the mitochondria of their cells, producing carbon dioxide and water as by-products.
In essence, energy flow in organisms starts with sunlight being captured by producers (like plants), which are then consumed by consumers (like animals), creating a complex web of energy transfer within the ecosystem.