The Organism -

Groups of similar cells working together (e.g., muscle tissue).

Scientists categorize every organism into three primary domains:

Physical features like a turtle's shell or a cactus's spines. The Organism

An organism is any individual living system, such as an animal, plant, fungus, or bacterium. To be considered "alive," an organism generally must:

Energy enters the system via the sun (plants), moves through consumers (animals), and is recycled by decomposers (fungi). Groups of similar cells working together (e

Internal processes like a snake producing venom or a human sweating to cool down. 5. The Organism and the Environment

Organisms with complex cells containing a nucleus. This includes: Protists: Mostly single-celled (amoebas). Fungi: Decomposers (mushrooms, molds). To be considered "alive," an organism generally must:

React to external changes in its environment. 2. The Hierarchy of Structure Organisms are organized in a "ladder" of complexity.