Natural selection, process that results in adaptation of an organism to its environment by means of selectively reproducing changes in its genotype. Variations that increase an organism's chances of survival and procreation are preserved and multiplied from generation to generation at the expense of less advantageous variations. As proposed by Charles Darwin, natural selection is the mechanism by which evolution occurs. It may arise from differences in survival, fertility, rate of development, mating success, or any other aspect of the life cycle. Mutation, gene flow, and genetic drift, all of which are random processes, also alter gene abundance. Natural selection moderates the effects of these processes because it multiplies the incidence of beneficial mutations over generations and eliminates harmful ones, since the organisms that carry them leave few or no descendants.
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Pollution exists in many forms and affects many different aspects of Earth’s environment. Point-source pollution comes from specific, locali...
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Air Pollution, addition of harmful substances to the atmosphere resulting in damage to the environment, human health, and quality of life. O...
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Soil is a mixture of mineral, plant, and animal materials that forms during a long process that may take thousands of years. It is necessary...
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Water Pollution, contamination of streams, lakes, underground water, bays, or oceans by substances harmful to living things. Water is necess...
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Solid wastes are unwanted solid materials such as garbage, paper, plastics and other synthetic materials, metals, and wood. Billions of tons...