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Give 2 examples of organisms exchanging substances with their environment.
Oxygen and carbon dioxide are transferred between cells and the environment during gas exchange
Urea diffuses from your cells into the blood plasma for removal from the body by the kidneys
What affects an organisms ability to exchange substances with its environment?
Surface area:volume ratio
Why don’t single celled organisms need exchange surfaces?
Gases and dissolved substances can diffuse directly into the cell across the cell membrane
large surface area compared to their volume,
substances can be exchanged across the membrane to supply the volume of the cell
Why do multicellular organisms need exchange surfaces?
smaller surface area compared to their volume
not enough substances can diffuse from their environment to supply their whole volume
Require exchange surfaces to increase the surface area for diffusion to allow enough of the necessary substances to pass through
How are exchange surfaces adapted to maximise effectiveness?
thin membrane: substances have a shorter distance to diffuse
Large surface area: lots of substances can diffuse at once
Animals → high blood supply: diffuse in and out of the blood faster
Ventilation in gas exchange surfaces: moves the air in and out of surface to allow more of the requires substance
Note 
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