Life has many hierarchical levels at which study may be done. Each level of biological structure has emergent properties. Cells are organism's basic units of structure and function. Regulatory mechanisms ensure a dynamic balance in living systems. Diversity and unity are the dual faces of life on Earth.
Evolution is a core theme of biology.
As a multidisciplinary process, science works by testing hypotheses and forming conclusions. Organisms depend on the cohesion of water molecules. Organisms are all made of Carbohydrates, Proteins, Lipids, Steroids and Nucleic acids. Organisms all have metabolic pathways. Organisms are open systems that interact continuously with their environment.