GAS EXCHANGE Flashcards
What adaptations do gas exchange surfaces have
1) large surface area
2) thin - for a short diffusion pathway
Where do single celled organisms exchange gases across
their body sirfaces
What process do single celled organisms use to absorb and release gases
diffusion
Where do single celled organisms diffuse gases in and out of
their outer sirface
How are single celled organisms adapted for gas exchange
1) large surface area: volume
2) thin
Why do single celled organisms have no need for a gas exchange system
oxygen can take part in biochemical reactions as soon as it diffuses into the cell
What is the internal network of tubes called for gas exchange inside an insect
tracheae
How are the tracheae supported and why
strengthened rings to stop them collapsing
What is the tracheae divided into
smaller dead-end tubes called tracheoles
How does air move into the tracheae
pores on surface called spiracles
What are tracheoles
smaller tubes that go to individual walls
How are tracheoles adapted for gas exchange
thin , permeable walls
How do respiratory gases move in and out of tracheal system
1) along a diffusion gradient
2) mass transport
3) end of tracheoles are filled with water
Explain respiratory gases move in and out of tracheal system through diffusion gradient
cells are respiring so use up oxygen meaning concentration at end of tubes falls and creates a diffusion gradient & diffusion in occurs.
C02 produced by cells during respiration which creates diffusion gradient in opposite direction & diffuses out
Explain respiratory gases move in and out of tracheal system by mass transport
contraction of muscles (rhythmic abdominal movements) can squeeze trachea, meaning mass movement occurs in and out
Exlpain respiratory gases move in and out of tracheal system through tracheoles filled with water
muscles around tracheoles respire anaerobically so lactate is produced which is soluble, so lowers water potential of muscle cells = water moves into cells. So volume of tracheal decreases and air drawn in
When would tracheoles filled with water occur
during times of major activity
How are spiracles opened and closed
by a valve`
What are the limitations of the tracheal system
relies on diffusion so needs a short diffusion pathway, meaning size of insects is limited
Why have fish deceloped gills
1) waterproof body = gas-tight
2) relatively large SA:V
3) lower concentration of O2 in water than air
Where are the gills located
within body of the fish, behind head
What are the gills made up of
gill filaments
What are at right angles to the gill filaments
gill lamellae
What do gill lamellae do
increase the surface area of the gill
What system do fish use for gas exchange
counter-current
What adaptations do lamellae have to increase rate of diffusion
lots of blood capillaries and thin surface layer = short diffusion pathway
What is the counter current system
blood flows in one direction and blood flows in the opposite
How does oxygen get to the gills
water containing oxygen enters through fishs mouth and is forced over the gills through openings on each side of its body
What does the counter current system ensure
that a large concentration gradient is maintained, allowing for maximum diffusion
How does the counter current system work (the countercurrent exhchange principal)
it means that no equilibrium is reached, as the oxygen concentration in the water is always slightly higher than that in the blood so diffusion always occurs
Draw the countercurrent flow graph
2 lines going parallel down, one always higher than the other
axis : distance along gill plate / saturation with O2
Draw the parallel flow graph
2 lines, one going up one going down that meet in the middle to form straight line
axis : distance along gill plate / saturation with O2
What is the other flow system to countercurrent
parallel flow
Which blood flows closest to the lamellae & which direction
deoxygenated, down
which blood flows in the centre of the gil l& which direction
oxygenated, up
How is gas exchange in plants similar to that pf insects
1) no living cell is far from external air so is near a source of 02/C02
2) diffusion takes place in gas phase (air) so it is more rapid than if it were in water
Where does gas exchange for dicotyledonous plants occur
surface of mesophyll cells
Where does gas exchange occur for most plants
in the leaves
How are leaves adapted for gas exchange
1) many small pores (stomata) and no cell is far from a stomata = short diffusion pathway
2) lots of interconnecting air-spaces that occur throughout mesophyll so gases can readily come in contact with mesophyll cells
3) large SA = rapid diffusion
What are the stomata surrounded by
guard cells
What do guard cells do and what does this mean
open and close the stomatal pore, means they can control the rate of gaseous exchange
Why do they need guard cells
so they can control water loss, through closing them when water loss would be excessive
How do guard cells open stomata
increase water content so become turgid and open stomatal pore
How do guard cells close stomata
decrease water contenct so become flacid and close stomatal pore
Where are mesphyll cells located
between upper and lower epidermis
Why do organisms need a method for preserving water
gas exchange requirs thin surface, which increases rate of water loss
What adaptations do insects have for conserving water loss
1) smal SA:V - minimise area water is lost from
2) waterproof, waxy outer skeleton (cuticle) over body
3) spiracles - openings around tracheae at body surface which can be closed, so can control water loss
4) hair around spiracles - reduces evaporation
What are the waxy cuticles of insects made of
chitin
Why can’t plants have a small SA:V
they photosynthesise which requires a large SA:V to capture light & exchange gases
What adaptations do terrestrial plants have to limit water loss
1) guard cells become flacid so close stomatal pore, limiting water loss
2) waterproof covering
What are xerophytes
plants adapted to living in areas with limited water supply
What adaptations do xeropytic plants have to limit water loss
1) thick cuticle - shortens pathway
2) curled leaves - stomata inside, protecting them from wind, traps water so increases water potential = minimum conc gradient
3) hairy leaves - trap moist air around stomata, smaller conc gradient
4) stomata in pits - trap moist air increasing conc gradient
5) reduced number of stomata - fewer areas to transpire from
What does wind do to the rates of evaporation and diffusion
increases it
How much water loss can occur via the cuticle
10%
Give and example of a plant with hairy leaves
heather plant
Give and example of a plant with sunken stomata
pine trees
What other plants have similar adaptations to xeropytes
plants in sand dunes, salt marshes, cold regiona
