Endogenous

Definition

Originating or developing from within an organism, tissue, or cell; produced or caused by internal rather than external factors. In arthropod biology, contrasts with exogenous processes such as environmental induction of diapause or external parasite acquisition.

Etymology

From Greek endon (within) + -genēs (born, produced)

Example

Endogenous circadian rhythms in insects such as Drosophila melanogaster persist under constant conditions, demonstrating internal clock mechanisms independent of environmental light cues.

Synonyms

• endogenic

Related Terms

• Exogenous
• Autogenous
• Circadian rhythm
• Diapause
• Hormone
• metabolism

Usage Notes

In entomology, often contrasts with exogenous: endogenous factors include genetic programming, hormonal milieu, and metabolic reserves, while exogenous factors include temperature, photoperiod, and food availability. In disease ecology, 'endogenous' may describe vertically transmitted (transovarial) symbionts or pathogens versus horizontally acquired (exogenous) infections. The term carries no implication of spontaneity—endogenous processes remain physiologically regulated.