AQA Biology A-Level Exchange
1. what affects the amount of material that is exchanged in an organism?:
size and metabolic rate- higher metabolic rate= more materials
exchanged
2. name 4 things that need to be exchanged between an organism and
their environment.: - respiratory gases
- nutrients
- excretory products
- heat
3. how do you calculate the surface area to volume ratio?:
4. how does gas exchange occur in a single-celled organism?: they are
small organisms so have a large surface area to volume ratio and
therefore can exchange substances through diffusion across their body
surface
5. how are respiratory gases moved in and out of an insect along a diffusion
gradient?: during cell respiration, O2 concentration at the end of
1/
, tracheoles de- creases so O2 from the atmosphere is drawn in by
diffusion along a concentration gradient. the CO2 produced goes the
opposite way
6. how are respiratory gases moved in and out of an insect using water that
fills the ends of the tracheoles?: during periods of high activity, muscles
carry out anaerobic respiration which produces lactate, a soluble liquid
that lowers water potential of muscle cells. this causes water to move
from tracheoles to the cells by osmosis. this causes water in tracheoles
to decrease in volume which draws air into them through a diffusion
gradient
7. what are spiracles and how do they work?: they are tiny pores on the
body surface of an insect that open and close using a valve. they can
allow water vapour to evaporate from them and tend to stay shut to
avoid water loss.
8. explain how the tracheal system limits the size of insects: it relies on
diffusion to bring oxygen to the respiring tissues. if insects were large it
would take too long for oxygen to reach all the tissues quickly enough
so the insect would die
9. why is there a conflict in insects between gas exchange and conserving
2/
1. what affects the amount of material that is exchanged in an organism?:
size and metabolic rate- higher metabolic rate= more materials
exchanged
2. name 4 things that need to be exchanged between an organism and
their environment.: - respiratory gases
- nutrients
- excretory products
- heat
3. how do you calculate the surface area to volume ratio?:
4. how does gas exchange occur in a single-celled organism?: they are
small organisms so have a large surface area to volume ratio and
therefore can exchange substances through diffusion across their body
surface
5. how are respiratory gases moved in and out of an insect along a diffusion
gradient?: during cell respiration, O2 concentration at the end of
1/
, tracheoles de- creases so O2 from the atmosphere is drawn in by
diffusion along a concentration gradient. the CO2 produced goes the
opposite way
6. how are respiratory gases moved in and out of an insect using water that
fills the ends of the tracheoles?: during periods of high activity, muscles
carry out anaerobic respiration which produces lactate, a soluble liquid
that lowers water potential of muscle cells. this causes water to move
from tracheoles to the cells by osmosis. this causes water in tracheoles
to decrease in volume which draws air into them through a diffusion
gradient
7. what are spiracles and how do they work?: they are tiny pores on the
body surface of an insect that open and close using a valve. they can
allow water vapour to evaporate from them and tend to stay shut to
avoid water loss.
8. explain how the tracheal system limits the size of insects: it relies on
diffusion to bring oxygen to the respiring tissues. if insects were large it
would take too long for oxygen to reach all the tissues quickly enough
so the insect would die
9. why is there a conflict in insects between gas exchange and conserving
2/
