Welcome to the world of biology. When we gaze at the stars or wander through a forest, a fundamental question often arises in our minds:What is life? In biological terms,an organism refers to an entity that exhibits life phenomena. To determine whether something is alive, we cannot rely on a single characteristic alone — we must follow the "principle of wholeness."

Core Scientific Logic

• Common Characteristics of Living Things: Nutrition, respiration, excretion, irritability, growth & reproduction, and heredity & variation. These six essential features are highly integrated — none can be omitted.
• The Nature of Metabolism: For example, photosynthesis (nutrition) and leaf shedding (excretion) in plants are not simple physical movements but complex biochemical reactions that maintain the order of life.
• Rigor in Determining Life: Although smart robots can move (irritability) and stalactites can grow (growth), they lack a complete metabolic system and genetic mechanism, so they are classified as non-living.