Why is mutation needed for evolution to occur, even though it usually has little effect on allele frequencies?

What is hydroelectric power produced by?

What is the importance of having the us forest service, the bureau of land management, the us fish and wildlife service, and the national park service? to manage land resources for conservation and the development of natural resources to manage land resources for conservation and the development of urban areas to preserve historical landmarks and manage the development of urban areas to preserve historical landmarks and manage the development of rural areas

How and why organisms are hierarchically classifies