1. Atoms: The basic building blocks of all matter, including living organisms.
2. Molecules: Two or more atoms bonded together. Examples include water (H₂O), carbon dioxide (CO₂), and proteins.
3. Organelles: Specialized structures within cells that carry out specific functions. Examples include the nucleus, mitochondria, and chloroplasts.
4. Cells: The fundamental unit of life, capable of carrying out all the processes necessary for life.
5. Tissues: Groups of similar cells that work together to perform a specific function. Examples include muscle tissue, nervous tissue, and connective tissue.
6. Organs: Structures composed of different tissues that work together to perform a complex function. Examples include the heart, lungs, and brain.
7. Organ Systems: Groups of organs that work together to carry out a major bodily function. Examples include the digestive system, circulatory system, and nervous system.
8. Organism: A complete living being made up of multiple organ systems.
9. Population: A group of individuals of the same species living in the same area.
10. Community: All the different populations of organisms living in a particular area.
11. Ecosystem: A community of organisms and their physical environment.
12. Biome: A large-scale ecosystem characterized by a particular climate and dominant plant and animal life. Examples include forests, deserts, and oceans.
13. Biosphere: The entire portion of Earth inhabited by living organisms.
