1. Atom: The most basic unit of matter. It is the smallest unit of an element that retains the chemical properties of that element. Examples include carbon, hydrogen, oxygen, and nitrogen.

2. Molecule: Two or more atoms bonded together. Examples include water (H₂O), glucose (C₆H₁₂O₆), and proteins.

3. Organelle: A specialized structure within a cell that carries out a specific function. Examples include the nucleus, mitochondria, and chloroplasts.

4. Cell: The basic unit of life. It is the smallest unit that can carry out all the processes necessary for life. Examples include nerve cells, muscle cells, and blood cells.

5. Tissue: A group of similar cells that work together to perform a specific function. Examples include muscle tissue, nervous tissue, and connective tissue.

6. Organ: A structure made up of different tissues that work together to perform a specific function. Examples include the heart, lungs, and stomach.

7. Organ System: A group of organs that work together to perform a specific function. Examples include the circulatory system, the respiratory system, and the digestive system.

8. Organism: A complete living being made up of multiple organ systems that work together to maintain life. Examples include humans, plants, and animals.

9. Population: A group of organisms of the same species living in the same area.

10. Community: A group of different populations living in the same area.

11. Ecosystem: A community of living organisms and their physical environment.

12. Biosphere: The part of Earth where life exists.

This hierarchy shows how life is organized from the simplest level to the most complex. Each level builds upon the one below it, and all levels are interconnected and dependent on each other.