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In order to survive, terrestrial organisms (those living
on land) must limit their water loss without compromising the efficiency of their gas-exchange systems
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These adaptations
of water loss and limited water supply is to reduce the
Limiting water loss in insects:
are essential because the rain quickly drains
rate at which water is lost through evaporation
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become dehydrated
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(holly leaves)
quires a thin, permeable surface with a large area (features
Plants living on salt marshes may have their
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Rolling up of leaves: most leaves have their stomata
conflict with the need to conserve water) so they have
roots drenched in water but find it difficult to
on the underside (lower epidermis) so the rolling of
adapted:
absorb it
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This beobtain water
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There is no water potentranspiration and survive
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In
leaf so there is no water loss
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Hairy leaves: thick layer of hair especially on the
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Limiting water loss

Spiracles—the openings of the tracheae at the body
surface and these can be closed to reduce water loss
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So they have a network of tracheae that
carry air containing oxygen directly to the tissues
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Certain plants have a restricted supply of water, have also
evolved a range of other adaptations to limit water loss
through transpiration, these plants are called xerophytes
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Without these adaptations these
plants would die
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The water potential gradient between the
inside and outside of the leaves is reduced = less
water lost
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(pine trees)
Reduced surface area to volume ratio of the leaves:
the smaller the SA to VR, the slower the diffusion
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This reduction in surface area is balanced
against the need for a sufficient area for photosynthesis to meet the requirements of the plant

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