DNA: All molecules, including this DNA molecule, are composed of atoms. 

Life's organization begins within cells. Macromolecules assemble into organelles like mitochondria and chloroplasts, performing vital cellular functions. Cells, the fundamental units of life, are either prokaryotic (lacking a nucleus) or eukaryotic (possessing a nucleus). Multicellular organisms organize cells into tissues, organs, and organ systems. An individual living entity, whether single-celled or multicellular, is considered an organism. Viruses, lacking cellular structure, are an exception.

Moving beyond individual organisms, a population consists of all individuals of a single species in a given area. Multiple populations interact to form a community. Communities, along with the non-living components of their environment, comprise an ecosystem. The biosphere, the highest level of organization, encompasses all ecosystems and represents the Earth's zones of life. This hierarchical structure, from organelles to the biosphere, illustrates the increasing complexity and interconnectedness of living systems.