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Unity and Diversity
Organisms and their Environment
Signatures of Life
Continuity and Change
10. Physiological adaptations for survival
Water holding frog - Cyclorana platycephala
Spinifex Hopping Mouse - Notomys alexis
Chapter 10 Flashcards
: Physiological adaptations for survival.
Desert plant plucks water from thin air:
Adapations in Desert Animals:
Plant and animal adaptations for survival in dry climates (from the SA museum):
Australian animals have adapted to arid habitats in diffe
How pests could overcome GM cotton toxins:
An unusual New Zealand plant adapted to predation by the extinct giant bird, the moa:
This site has several examples of the ways that animals survive in the American deserts:
which involves transgenerational adjustment, physiological
is generally narrow in scope and involves
to a particular, usually narrow, range of
. Examples of physiological adaptation are
tanning of skin
when exposed to sun over long periods, the
formation of callouses
on hands in response to repeated contact or pressure, and the ability of certain organisms to absorb nutrients under low
painted turtle, for example,
hibernates without oxygen.
Physiological Adaptations of Plants that reduce water loss.
Fewer stomata, the pores in the epidermis or skin of the leaf on the leaf can reduce water loss
In hot dry climates many plants open their stomata only in the cool of the evening.
Small leaves (totora, lavender) have a reduced surface area to enable plants to conserve water, as do feathery, filigree leaves (romneya, eschscholzia or Californian poppy).Many xerophytic plants such as pine and heather, have small, needle shaped leaves which are often circular in cross section. This reduces the surface area and hence the evaporating surface.
Needle-like foliage (grasses, pine trees) has a very small surface area that looses very little water. Some of these plants can roll their leaves inwards, further reducing surface areas and water loss.
Leafless plants, such as brooms, have lost their leaves altogether with stems undertaking essential photosynthesis and food production.
Grey or light coloured foliage reflects light, reducing heat and thus water loss from transpiration
Thicker cuticles, the outer waxy coating on leaves, slows transpiration; many coastal plants have a thick glossy coating on the leaves, reducing water loss and also protecting from salt-burn.(think shiny leaf hedges and
). Found in many evergreen leaves, the cuticle cuts down water loss in two ways: it acts as a barrier to evaporation and also the shiny surface reflects heat and so lowers temperature.
Silver hairs coating leaves reflect light and help to lower temperatures inside the leaf, as well as reducing the effect of drying winds.
Thick fleshy leaves can store water; many succulents have thick leaves that, when bruised or broken, contain a great deal of moisture.
Sunken stomata - stomata may be sunk in pits in the epidermis; moist air trapped here lengthens the diffusion pathway and reduces evaporation rate.
Leaf rolled with stomata inside - this adaptation is found in Marram grass (
). As can be seen from the image left, the inner surface is covered in hairs. The rolled leaf and hairs both serve to trap moist air so reducing transpiration. In addition, a smaller surface area of leaf is exposed to the drying effects of the wind.
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