Evolutionary Significance of Symbiosis in Ecosystem Development
Authors: Ajay Kumar, Aman Jaiswal*, Deepak Kumar, Shekher Kumar,
Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi (India) 110 012
*Corresponding author e-mail: amanjaiswal1989@gmail.com

The term "symbiosis" was first coined by Anton de Bary in the mid-19th century as 'the living together of different species 'Symbioses are prolonged associations between organisms often widely separated phylogenetically. Temporarily or for a longer time and at least one of the organisms benefits from the relationship. Symbiosis established due to direct transmission and re-infection. Symbiosis functions in nutrition, protection, space and is selective driver for evolution. Symbiosis varies with respect to: Degree of intimacy (ectosymbiosis vs. endosymbiosis), the balance of advantage (mutualism vs. parasitism) and the extent of dependence (facultative vs. obligate symbiosis).

Symbiosis - A driving force in evolution

Microbial symbionts play such an important role in the lives of their eukaryotic hosts, why should they not also play a role in the evolution of these higher organisms? Symbiotic relationships are recognized as an important selective force behind evolution. Interdependent coevolution took place in many species. Over many generations, the organisms came to depend more on the symbiosis as natural selection favored those traits. Thus symbiosis became the sole source of the food, shelter, enzyme or whatever else the symbiotes derived from one another.

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