Gases move across a respiratory surface through the process of diffusion, driven by differences in partial pressure. Oxygen moves from areas of higher concentration in the external environment into the bloodstream, while carbon dioxide, which is at a higher concentration in the blood, diffuses out into the external environment. This exchange occurs across thin, moist membranes, where the gases can easily pass through. Factors such as surface area, thickness of the membrane, and ventilation also influence the efficiency of gas exchange.
ventilation
Diffusion
In unicellular organisms, gases are exchanged through simple diffusion across the cell membrane. Oxygen from the environment diffuses into the cell, while carbon dioxide produced by the cell diffuses out. This process is driven by concentration gradients, where gases move from areas of higher concentration to areas of lower concentration.
Cilia help to move substances across the surface of a cell. They can either help propel fluids over the cell's surface, as in the respiratory tract, or help move the cell itself, as in the case of sperm cells. They also play a role in sensory functions in some cells.
Glaciers are large bodies of ice and compacted snow that move across the Earth's surface. Icebergs are large bodies of compacted ice and snow in cold oceans, but the biggest mass sits below the water line. Icebergs do not move across the Earth's surface, but instead, the water's surface.
it remains unchanged
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Material moves from the respiratory system to the circulatory system by diffusing across a membrane in the air sacks called alveoli.
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Because if it all stays in then your body will keep in this poisons gases. http://wiki.answers.com/Why_does_air_move_in_our_out_of_your_respiratory_system#ixzz1ZCdvdlbk
Material moves from the respiratory system to the circulatory system by diffusing across a membrane in the air sacks called alveoli.
The idea that continents move slowly across the earth's surface is called the continental drift.