Biological Organization, Level of

a biological system with a specific scope and organizational principle.

The components of levels of biological organization interact among one another, and the levels themselves interact in an individualized manner with lower and higher levels. The principal levels of biological organization are molecular, organismic, populational, specific, and biospheric. A more detailed classification includes cellular and tissue levels of biological organization. Outside the scope of biology there are levels lower than those of molecules, including levels involving atoms, electrons, protons, and other nuclear particles. There are also levels higher than that of the biosphere—those of the earth, the heavenly bodies, and the cosmos.

The concept of levels of biological organizations is broad and applies to systems whose existence is based on relationships that unite their component parts into a whole. The relationships within each level of biological organization are unique to that level. For example, biochemical processes and physical forces operate within a cell, and the organisms living in a body of water, while distinct from one another, constitute an individualized and relatively stable ecological system united by a common system of interrelationships involving matter and food.

Owing to the systemic nature of living organisms, levels of biological organization are sharply distinguished from one another. When the general system of biological organization becomes more complex, the system of a lower level becomes part of the next higher system, which in turn becomes part of a yet higher system. This phenomenon indicates the existence of hierarchical levels of biological organization. The hierarchical progression of levels of biological organization corresponds to and results from the history of the development of living organisms. The accepted view of the origin of life maintains that life evolved from organic molecules which were formed independently of living organisms. These organic molecules were followed by primitive forerunners of cells and then by cells and multicellular organisms.

Each level of biological organization is studied within a specific biological discipline. The fields of biochemistry, molecular biology, molecular genetics, bio-organic chemistry, and biophysics deal with the molecular level, cytology with the cellular level, physiology with the organismic level, and population genetics, ecology, and taxonomy with the populational and specific level.

Systems analysis is the study of complex and diverse hierarchical systems, including the hierarchical system of human society. Living organisms, with their many variable factors and internal interrelationships, are included in such systems. The general theory of systems developed by L. von Bertalanffy had its origin in biology. The concept of levels of biological organization, which is closely related to the theory of systems, is essentially a dialectical materialist concept, since it elucidates the integrity and distinctiveness of biological entities by means of material factors. The concept of levels of biological organization is an important means for the understanding of biological laws.