* Organism: A single, living individual (e.g., a tree, a fish, a human).
* Population: A group of individuals of the same species living in the same area (e.g., all the oak trees in a forest, all the salmon in a river).
* Community: All the different populations of organisms that live and interact within a given area (e.g., all the plants, animals, fungi, bacteria in a forest).
* Ecosystem: A community of organisms interacting with their physical environment (e.g., a forest, a coral reef, a desert).
* Biosphere: The entire portion of Earth that supports life, including all the ecosystems and their interactions (e.g., the Earth's atmosphere, land, water, and all living things).
