He wondered how this happened. He also noted that within a species there are individual variations. He suspected that some source of this variation was part of the animal's hereditary make up and as a result these variations were passed along to offspring. It was these observations that led Darwin to suggest the process of natural selection. Thus, the individuals that are most fit to deal with the environment are the ones who reach adulthood and are the ones who are most likely to reproduce.
Natural selection is the driving force of evolution.
It is the selective breeding that results from the obstacles to reproduction that are imposed by the natural environment. Evolution can occur slowly, fast, or not at all depending on the rate and type of environmental change and athe amount of variation that exists among members of a species. An individual or species that changes in response to the demands of its environment is adapting to these new demands. Genetic makeup of moths now specify black color. Humans use words to pass on what has been learned.