The levels of organization in biology describe a hierarchy from the simplest to the most complex structures that make up life. These levels are:

• Atom : The smallest unit of matter.
• Molecule : Two or more atoms bonded together.
• Macromolecule : Large molecules formed by polymerization, such as DNA.
• Organelle : Structures within cells that perform specific functions (e.g., mitochondria).
• Cell : The basic unit of life; can be prokaryotic or eukaryotic.
• Tissue : Groups of similar cells working together to perform a function.
• Organ : Structures made of different tissues working together (e.g., heart, liver).
• Organ system : Groups of organs that perform related functions (e.g., circulatory system).
• Organism : An individual living entity, either unicellular or multicellular.
• Population : A group of individuals of the same species living in a specific area.
• Community : All populations of different species living and interacting in an area.
• Ecosystem : A community plus the abiotic (nonliving) environment.
• Biosphere : The sum of all ecosystems on Earth, encompassing all life and environments

This hierarchical organization reflects increasing complexity and integration, from atoms up to the global scale of the biosphere.