gas exchange in plants and animals Flashcards
5 features of a specialised gas exchange surface
- high surface area to volume ratio to increase rate of exchange
- very thin, small diffusion pathway so faster rate of diffusion
- selectively permeable to allow selected materials to cross
- movement of the environment medium (eg air) to maintain a diffusion gradient
- a transport system to ensure the movement of the internal medium (eg blood) to maintain diffusion gradient
ficks law
surface area x concentration difference
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length of diffusion path
is diffusion more rapid in air or water
air
how is a leaf adapted for efficient gas exchange
large SA to volume ratio
very short diffusion pathway
air spaces in the spongy mesophyll layer
how do guard cells open and close stomata
when water enters guard cells swell and become turgid
thin elastic wall stretches with turgor pressure
thicker inelastic cell wall (against opening) does not
what is a xerophyte
plants that are adapted to living in areas where their water losses due to transpiration may exceed their water uptake.
cuticle
forms a waterproof barrier
the thicker the cuticle the less water can escape
hairy leaves
traps still moist air next to leaf surface
reduces water potential gradient
less water lost by evaporation
rolling leaves
protects lower epidermis from outside helps trap air within the leaf
region becomes saturated with water
water potential gradient disappears
stomata in pits/grooves
traps moist air next to the leaf,reducing water potential gradient
reduced SA:vol ratio
thin needles
reduce SA
reduce water loss
(but need to have enough SA for sufficient photosynthesis)
what is the internal system of tubes where gas exchange takes place in insects called
trachea
what are the smaller dead wand tubes of the trachea called
tracheoles
what are the open ends of the trachea called
spiracles
how is the diffusion gradient in the insect tracheal system maintained
O2 used up so concentration towards tracheole falls
creates a diffusion gradient
