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Revision for AS OCR Biology ­ Topic 4 (Exchange Surfaces and Breathing)

Organisms exchange substances such as carbon dioxide, oxygen, nutrients and urea.
In singlecelled organisms, these substances can easily diffuse into and out of the cell. They have a small
surface area to volume ratio.
However, in multicellular organisms,…

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A spirometer records the tidal volume, vital capacity, breathing rate and oxygen consumption of a person.
A spirometer consists of an oxygenfilled chamber with a moveable lid.
A person breathes through a tube which is connected to the oxygenfilled chamber.
As the person breathes in an out, the lid…




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