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Biology (from the Greek words “bios” life and “logos” study) is the science of life. Biologists deals with all the physicochemical aspects of life, study the structure, function, growth, origin, evolution, and distribution of living organisms.

Aspects of biological science range from the study of molecular mechanisms in cells to the classification and behavior of organisms, how species evolve, and interaction between ecosystems.


Biology often overlaps with other sciences; for example, biochemistry and toxicology with biology, chemistry, and medicine; biophysics with biology and physics; stratigraphy with biology and geography; astrobiology with biology and astronomy.

Social sciences such as geography, philosophy, psychology, and sociology can also interact with biology, for example, in the administration of biological resources, developmental biology, biogeography, evolutionary psychology, and ethics.

Basic concepts of biology

  • Cell theory
  • Homeostasis
  • Unity (characteristics in common) – life originated on Earth have a sameness of basic structure, composition, and function would seem to indicate that only one original type succeeded. A common origin of life would explain why in plants, animals, humans or bacteria—and all forms of life in between—the same chemical substance, the deoxyribonucleic acid (DNA), in the form of genes accounts for the ability of all living matter to replicate itself exactly and to transmit genetic information from parent to offspring. Furthermore, the mechanisms for that transmittal follow a pattern that is the same in all organisms.
  • Evolution
  • Diversity
  • Behaviour and interrelationships – the study of the relationships of living things to each other and their environment is known as ecology.
  • Continuity – the ability of an organism to reproduce is one of the essential characteristics of life. Because life comes only from preexisting life, it is only through reproduction that successive generations can carry on the properties of a species.

Branches of biology