are the small sacs that are the site of gas exchange in the lungs. In addition to being an airway, the is the location of the human vocal cords. Cilia in cells along the trachea and nasal passages secrete which traps dirt and particles from the air. Air is only approximately 21% oxygen. The majority of air is . The medulla oblongata controls the contraction and relaxation of the , causing the lungs to inflate and deflate during breathing. Explain the process of breathing. Begin with inhalation and describe the route that the air takes to the lungs, and what happens when the air reaches the lungs. Include in your description the terms: mouth, nose, pharynx, larynx, trachea, bronchi, lungs, alveoli, carbon dioxide, oxygen, and capillaries.

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

a community that experiences major changes undergoes progress