1. Atom: The basic unit of matter, composed of protons, neutrons, and electrons.
2. Molecule: Two or more atoms held together by chemical bonds.
3. Organelle: A specialized structure within a cell that performs a specific function (e.g., nucleus, mitochondria).
4. Cell: The basic unit of life, capable of carrying out all life processes.
5. Tissue: A group of similar cells working together to perform a specific function.
6. Organ: A structure composed of different tissues working together to perform a specific function.
7. Organ System: A group of organs that work together to carry out major bodily functions.
8. Organism: A complete living being made up of organ systems.
9. Population: A group of organisms of the same species living in the same area.
10. Community: All the different populations of organisms living and interacting in the same area.
11. Ecosystem: A community of organisms and their physical environment.
12. Biosphere: All the living organisms and their physical environment on Earth.
