A gene pool refers to the combination of all the genes, or genetic information, in any population, usually of a particular species. A large gene pool indicates extensive genetic diversity, which is better able to withstand environmental challenges. In contrast, inbreeding contributes to a smaller gene pool, making populations or species less able to adapt and survive when faced with environmental challenges. The composition of a populations gene pool can change over time through evolution, which can occur by a variety of mechanisms, including mutations, natural selection, and genetic drift. The result is a gene pool that is altered to be attuned to the needs of the populations specific environment. The ability of a population to adapt and evolve is thought to be influenced in part by the size of its gene pool. A large and diverse gene pool may improve a populations chances for future adaptation to changing environmental conditions. Populations with smaller, narrower gene pools, on the other hand, may be less successful when confronted with swift environmental change.