Slides in this set
Exchange with the environment
Four things need to be exchanged between
organisms and their environment:
· Respiratory gases
This can be done in two ways:
· Passively…read more
Large topic broken down into sub topics
- Features of Gas exchange surfaces
- Single-celled organisms
How different organisms deal with the same
problem in different ways…read more
Surface area to volume ratio plays a big part in how
organisms are made to over come the problem of
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
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