A variance is an exception to one or more of the zoning restrictions on a piece of property. A variance is different from a nonconforming use, which permits existing structures and uses to continue when zoning is first instituted.
The book, On The Origin Of Species,  suggested  that organisms evolve through the process of natural selection.opulations evolve as the individual organisms less able to survive in the current environment die and fail to reproduce. That is natural selection.
Darwin's theory of evolution by natural selection assumed that tiny adaptations occur in organisms constantly over exceptionally long periods of time. Gradually, a new species develops that is distinct from its ancestors.volution. n. 1. (Biology) biology a gradual change in the characteristics of a population of animals or plants over successive generations: accounts for the origin of existing species from ancestors unlike them. See also natural selection.