An organism is a living entity that can function independently. It can be as simple as a single-celled bacterium or as complex as a human being. Organisms are characterized by their ability to grow, reproduce, respond to stimuli, and maintain homeostasis, which is the process of keeping their internal environment stable. Organisms can be classified into different categories, such as plants, animals, fungi, and microorganisms. Each category has unique features and functions. For example, plants produce their own food through photosynthesis, while animals typically consume other organisms for energy. Understanding organisms is essential for studying life and ecosystems.