Biological organization

Biological organization is the hierarchy of complex biological structures and systems that define life using a reductionistic approach. The traditional hierarchy, as detailed below, extends from atoms to biospheres. The higher levels of this scheme are often referred to as an ecological organization concept, or as the field, hierarchical ecology.

Levels of organization

Each level in the hierarchy represents an increase in organizational complexity, with each "object" being primarily composed of the previous level's basic unit.

Molecular Level

The molecular level in biological organization involves the smallest units in terms of molecular biology. This includes atoms, the smallest units retaining properties of elements, which come together to form molecules like water, proteins, carbohydrates, nucleic acids, and lipids.

Cellular Level

The cellular level consists of cells, the basic unit of life. Some organisms, such as bacteria, are unicellular. Other organisms like humans are multicellular.

Organ Level

The organ level involves a series of cells that come together to perform a specific function. Examples include the heart, lung, and liver. These organs work together in organ systems to carry out major bodily functions.

Organism Level

The organism level is the level at which all organ systems come together to form a complete, living organism. This can range from small organisms like bacteria to large organisms like elephants.

Population Level

The population level involves groups of a single species living in a specific area. For example, a group of humans living in a city would be considered a population.

Community Level

The community level involves multiple populations of different species living in a specific area. For example, a forest of trees and undergrowth plants, inhabited by animals and rooted in soil containing bacteria and fungi, constitutes a biological community.

Ecosystem Level

The ecosystem level involves all the living things in a particular area along with all the nonliving components of the environment with which life interacts, such as air, soil, water, and sunlight.

Biosphere Level

The biosphere level is the global ecological system integrating all living beings and their relationships. This includes their interactions with the elements of the lithosphere, hydrosphere, and atmosphere.

See also

• Hierarchy theory
• Systems biology
• Complex systems
• Emergence