Unit 1 section 3 Exchange Surfaces
- Created by: stephloupoole
- Created on: 16-04-14 17:06
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- Exchange Surfaces
- exchange of substances with the environment
- every organism, whatever its size needs to exchange things with its environment
- Cells need to take in oxygen and nutrients
- they also need to excrete waste products like carbon dioxide and urea
- how easy it is to exchange substances depends on the organisms surface area to volume ratio
- Specialist exchange organs
- an organism needs to supply every one of its cells with substances like glucose and oxygen
- it also needs to remove waste products from every cell to avoid damaging itself
- single celled organisms exchange substances differently to multicellular organisms
- Single celled Organisms
- substances can diffuse directly into or out of the cell across the cell membrane
- the diffusion rate is quick because of the short distance the susbstance has to travel
- single celled organisms have a relatively high surface area to volume ratio
- Multicellular Organisms
- diffusion across the outer membrane is too slow
- some cells are deep within the body
- larger animals have a low surface area to volume ratio
- diffusion across the outer membrane is too slow
- Single celled Organisms
- exchange of substances with the environment
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