What Are the Levels of Organization in Biology?

Levels of the organization – Biology

Hierarchical levels of organization of living things

    According to “The Cell Theory,” The cell is the basic structural and functional unit of life. Some organisms are unicellular, while others are multicellular. A cell is composed of several organelles which are formed by different organic molecules. Then the Levels of Organization in Biology can be build up by using relevant examples at each level.

Molecules, Organelles, Cells, Tissues, Organs, Organ Systems, Organisms, Populations, Communities, Ecosystems, Biosphere

Individual organism; 

  • The individual organism is One member of a given species. Individual organisms interact with the environment for most of their needs.
  •  E.g., An elephant


  • A population is defined as “A group of individuals of the same species which live interacting with each other in a defined area in a given time.”
  •  E.g., the Elephant population in Sri Lanka in 2009.
  • A population has features such as growth rate, density, intraspecific competition, etc.


  • Populations of different species in a particular area interacting with each other
  • E.g., Animal Community of Yala National Park.
  • Interactions among populations include predatory, herbivorous, and symbiotic relationships.


  • The functional/dynamic unit is comprising all living organisms in a community and the abiotic environment, which interacts with each other.  E.g., a forest


  • The sizeable functional system comprising all ecosystems on earth.


Living organisms show a wide range of variations in size, shape, form, and distribution.

• Size – Bacteria – 0.25  – 2 9 to Giant Sequoia (Giant Red Wood)– 100m

• Shape – Organisms are diverse in shape, and some organisms are symmetrical while others are asymmetrical

• Form – acellular, unicellular, multicellular

• Distribution – Terrestrial, aquatic, arboreal, aerial