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Gas exchange in single-celled organisms:
These are small so have a large surface area
to volume ratio
...


Respiratory gases move in and out of the tracheal system
in three ways:
1
...
CO2 creates a diffusion gradient in the other
direction (moves along tracheoles-tracheae to atmosphere)
...


Mass Transport—contraction of muscles can squeeze
the trachea, enabling mass movements of air in and
out
...


Gas exchange in insects:
Insects have evolved mechanisms to conserve water
...

Gas exchange:
Insects have evolved an internal network of tubes
called tracheae
...

ened rings to prevent them collapsing
...

These extend throughout all the body tissues of
the insect
...

Water moves from tracheoles into cells by osmosis
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Gases enter and leave tracheae through tiny pores called spiracles on the
body surface
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When they are
open, water vapour can evaporate from the insect
...
Periodically they open them for
gas exchange
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As a result, length of diffusion pathway limits
the size that insects can attain
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Exchange in single-celled
organisms and insects



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