This guide breaks down —the fundamental unit of life—from its basic building blocks to how it survives in a complex world. 1. What Defines an Organism?

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

Create new individual organisms (sexually or asexually).

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

Regulate its internal environment (like temperature or pH).

Heterotrophs (must eat other organisms for energy). 4. Survival Mechanisms

Single-celled, often found in extreme environments like hot springs or salt lakes.