This document discusses the characteristics of living things and provides examples. It defines what classifies something as living, including the abilities to respond to stimuli, obtain and use energy, grow, reproduce, and be composed of cells. It then applies these criteria to determine that barnacles are living organisms. The document also discusses the organization of living systems like the human body from the molecular level to cells to tissues to organs and organ systems. Finally, it briefly introduces the concept of homeostasis, or an organism's ability to maintain stable internal conditions in response to external changes.
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