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By the end of the lesson...
· Describe the features of a gas exchange
surface
· Explain how insects overcome challenges of
gas exchange…read more

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Exchange with the environment
Four things need to be exchanged between
organisms and their environment:
· Respiratory gases
· Nutrients
· Waste
· Heat
This can be done in two ways:
· Actively
· Passively…read more

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GAS EXCHANGE
Large topic broken down into sub topics
- Features of Gas exchange surfaces
- Single-celled organisms
- Insects
- Fish
- Plants
How different organisms deal with the same
problem in different ways…read more

Slide 5

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Gas exchange
Surface area to volume ratio plays a big part in how
organisms are made to over come the problem of
gas exchange.
All cells need a supply and to get rid of waste.
Single celled organisms have a large SA:V so gas can
diffuse across the membrane (O2 in and CO2 out).
Even when covered by a cell wall this is fully
permeable to these gases.
But how do larger organisms cope?…read more

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As organisms become larger the SA/V decreases.
Simple diffusion would not work to meet the need
of all cells ­ not enough diffusion
­ take too long to get to the centre
To tackle this, multicellular organisms have evolved
one of two features:
- flattened shape (no cell far from surface)
- specialised exchange surfaces…read more

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