Gaseous Exchange and Water Loss in Terrestrial Insects

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  • Created on: 10-05-16 11:58
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Gas Exchange in Terrestrial Insects
Even though some insects are quite small they're very active and therefore
need to be able to respire quickly
Inside they have a very efficient tracheal system which is a network of
The trachea branch off into tracheoles that carry air directly to the cells
o The branching increases the surface area which in turn increases the
rate of gas exchange through simple diffusion ­ like alveoli
o The tracheoles also have thin, permeable walls which again increases
the rate of diffusion
o Another way the tracheoles are adapted to efficient gas exchange is by
being able to fill up with fluid
When the insect is at rest, water diffuses out of its cells into the
ends of the tracheoles which reduces the surface area in contact
with the cells and reduces the rate of diffusion.
When insects are more active, eg flying, their muscle cells
produce lactic acid, which lowers the water potential in the cells
so the water diffuses by osmosis from the tracheoles into the
muscle cells.
O2 moves down it's concentration gradient directly into cells
CO2 moves down its concentration gradient towards the spiracles and is
released into the atmosphere
Water Loss in Terrestrial Insects
One way water loss is prevented is by the rigid, chitinous exoskeleton that
insects have on the outside of their body as well as a waxy cuticle
o This allows them to be waterproof and prevents the insect from drying
The insect can also open and close their spiracles which have tiny hairs to
prevent water loss as well


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