Theory of natural selection
Charles Darwin gave the theory of natural selection. The main features of the theory of natural selection are:
● To increase survival rates most organisms (usually lower groups) reproduce to a large extent.
● Although the rate of reproduction increases the resources available are limited.
● These limited resources cause a struggle for survival.
● Only organisms that have an advantageous variation are better adapted to the environment.
● The organisms that are better adapted are able to survive, reproduce and are fit.
Survival of the fit
In Darwinian terms the phrase “Survival of the fit” is best understood as "Survival of the form that will leave the most copies of itself in successive generations."
Therefore survival of the fittest means those that survive are called fit.