Biological organisation

Biological organisation or biological hierarchy 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 organisation concept, or as the field, hierarchical ecology.

Overview

Every organism is organised, although the degree of organisation varies greatly among different types of organisms. Organisms are composed of a number of different biological units. At the lowest level of the biological hierarchy are the atoms that make up matter. These atoms combine to form molecules, which in turn form organelles and other cellular structures.

Levels of organisation

The biological organisation of life is a fundamental premise of science, which perceives that life is structured from simple to complex levels. The following are the main levels of biological organisation:

• Atom: This is the most basic unit of matter.
• Molecule: A group of atoms bonded together represents the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.
• Macromolecule: It is a very large molecule, such as protein, commonly created by the polymerization of smaller subunits called monomers.
• Organelle: A specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer.
• Cell: The basic unit of all life. Some organisms, such as bacteria, are unicellular. Other organisms like humans are multicellular.
• Tissue: A tissue is a group of cells that work together to perform a specific function.
• Organ: An organ is a group of tissues that perform a specific function or group of functions.
• Organ system: An organ system is a group of organs that work together to perform a major function.
• Organism: An organism is a living entity consisting of one or more cells.
• Population: In biology, a population is a set of individuals of the same species living in a particular area.
• Community: A community is a set of populations of different species living in a particular area.
• Ecosystem: An ecosystem consists of all the living things in a particular area together with the abiotic, non-living parts of that environment such as nitrogen in the soil or rainwater.
• Biome: A biome is a collection of ecosystems sharing similar climatic conditions.
• Biosphere: The biosphere comprises all life on Earth and all parts of the Earth in which life exists, including land, water, and the atmosphere.

See also

• Hierarchy of life
• Complex system
• Systems biology
• Emergence