The variety in a species comes through in DNA. When a new and helpful mutation arises, it will help individuals in the species to better . Over the following generations, the new trait will become more prominent in a population (or even essential) since it increases the chances of . (For example, the first bats to fly would have had an advantage over other bats who did not have the new genes necessary. The flight gene likely quickly during the following generations since it is so useful for survival.)

increase soil erosion                                             reduce soil erosion

cattle grazing                                                         hydroseeding

deforestation                                                         contour plowing

                                                                                planting vegetation

plant roots basically hold the top soil

together and stop soil erosion because

in such situation top soil is not removed

during flood but cattle grazing causes

soil erosion because cattle consume the

grasses and herbs and top soil is exposed.

same situation occurs because of

deforestation, the trees and plants are cut

down to expose top soil which causes soil

erosion