ORGANIC EVOLUTION (BIOLOGY)

The changes in the environmental conditions to which the organisms respond are known as stimuli. Every living organism responds when an external stimulus acts on it. A stimulus is a change in the external or internal environment which brings about a physiological response, i.e. when applied to any sensory receptor it elicits action or response.

Adaptation is a feature that helps an organism, such as a plant or animal survive in its environment. It is common in a population because it provides some improved function. It enables a plant or an animal to live in a particular habitat.

On the Origin of Species (On the Origin of Species by Means of Natural Selection), published on 24 November 1859, is a work of scientific literature by Charles Darwin which is considered to be the foundation of evolutionary biology. It introduced the idea that different populations evolve over the course of generations through a process of natural selection.

The theory of evolution is a shortened form of the term "theory of evolution by natural selection," which was proposed by Charles Darwin and Alfred Russel Wallace in the nineteenth century.

'Survival of the fittest' is a phrase that originated from Darwinian evolutionary theory as a way of describing the mechanism of natural selection. Herbert Spencer first used the phrase, after reading Charles Darwin's On the Origin of Species, in his Principles of Biology (1864), in which he drew parallels between his economic theories and Darwin's biological ones.