Levels of organization

1. Atoms: Atoms are the smallest units that make up living things. The most important ones are: Carbon (C) , Oxygen (O), Hydrogen (H), Nitrogen (N), Phosphorus (P), ...

2. Molecules​: Molecules are a group of two or more atoms. The molecules that can only be found in living beings are called biomolecules​. Biomolecules are: ●Inorganic biomolecules​:​ Water and mineral salts. ●Organic biomolecules​:​ Carbohydrates, Lipids, Proteins and Nucleic Acids.

3. Organelles: They are little structures inside the cells. Each one performs a different function.

4. Cells : They are the smallest living beings, the simplest ones. Atoms, biomolecules and organelles are components of cells, but are not alive. Cells and upper levels are alive.

5. Tissues:​ They are groups of specialized cells that work together to perform a function.

6. Organs​: They are groups of different tissues working together to perform a function.

7. Organ systems​: They are groups of organs working together to perform a function.

8. Organisms​: They are independant living things made up of organ systems that can carry out all the life functions: Nutrition, Interaction and Reproduction.