3.3.1 AXHANGE
As an organ1sm becomes larger, the surfuce area to volume rato decreases
Small organsms can exchange substances drectly with their environment
Large organisms either have o flattened shape (no cell for from surfoce) Or
speialised exchange surfaces
Specal1sed exchange surfaces!
lorge surfae area
-
short diffusion distance
selectively permeable
ditfusion grodient
transport system
3.3.2 Cras exchanqe in single-celled orguniss
Large surface area to volume rat1o
Diffusion of qases across cell surfoce membrane
CTas exchange in insects
Insccts have a larye surface area to volume ratio have to balance water loss with
qas exchange. Their outer body wall cover ed in wax prevents exeess watee loss
but also prevents gas enchange across body sur foce
Sp1rade Trachea
Jracheoles
Chtn body
Surfae with
(exchonge
surtace)
bwaxy coveing
Spirade- valve opens when cO, levels n tissues are hiqh m1nimises water loss
Tracheoe- rinys of chitn keep arways open
Ar sacs store aur, reducing need to optn sprrscles
Trocheolcs highly branched for large surtue area and close to lot ot cells
thin walls tor short ditfusion distance
Movement of abdoninal muscles may incease airflow by punpng
Limiting water loss in insectsi
Small Surface area to olume ratio
chit1n body susfae wth woxy couering
sprades
, 332 GAS LXHANGt
Gas Cxchange in fsh
Fish have a waterproof, gas taht outer cover ing and small surfue area to volume rat1o.
They have evolvedo speialsed qas exchan ge system yills
water flow deoxygenoted
blocd
oxygnated
blood lomellae
Flaw of water and flow of blood are n oppaste directron s comtercurrent flow
lhis mantans a diffuson qrodient so equlibr1um never estalol1shed and oxygen
alway move trom water to bloc d. Ditfusign qradent avoss length of lamelac.
Adaptat1on of alls
many filaments covered with lots of lamellae proude alarge surtace area
sngle laye ot epthelad cells whch qive ashort ditfusion distance
cCuniercurrent flow along whoie gll mantans dofusion dradient and egulibrum
is never rached. Ditfusion gadient along length of lanela
fish nave a one way ventilation systen water flows over the gills.
water Is much denser than air so (sis difficult to move two
ways
more streamlned
wate support the qilh
As an organ1sm becomes larger, the surfuce area to volume rato decreases
Small organsms can exchange substances drectly with their environment
Large organisms either have o flattened shape (no cell for from surfoce) Or
speialised exchange surfaces
Specal1sed exchange surfaces!
lorge surfae area
-
short diffusion distance
selectively permeable
ditfusion grodient
transport system
3.3.2 Cras exchanqe in single-celled orguniss
Large surface area to volume rat1o
Diffusion of qases across cell surfoce membrane
CTas exchange in insects
Insccts have a larye surface area to volume ratio have to balance water loss with
qas exchange. Their outer body wall cover ed in wax prevents exeess watee loss
but also prevents gas enchange across body sur foce
Sp1rade Trachea
Jracheoles
Chtn body
Surfae with
(exchonge
surtace)
bwaxy coveing
Spirade- valve opens when cO, levels n tissues are hiqh m1nimises water loss
Tracheoe- rinys of chitn keep arways open
Ar sacs store aur, reducing need to optn sprrscles
Trocheolcs highly branched for large surtue area and close to lot ot cells
thin walls tor short ditfusion distance
Movement of abdoninal muscles may incease airflow by punpng
Limiting water loss in insectsi
Small Surface area to olume ratio
chit1n body susfae wth woxy couering
sprades
, 332 GAS LXHANGt
Gas Cxchange in fsh
Fish have a waterproof, gas taht outer cover ing and small surfue area to volume rat1o.
They have evolvedo speialsed qas exchan ge system yills
water flow deoxygenoted
blocd
oxygnated
blood lomellae
Flaw of water and flow of blood are n oppaste directron s comtercurrent flow
lhis mantans a diffuson qrodient so equlibr1um never estalol1shed and oxygen
alway move trom water to bloc d. Ditfusign qradent avoss length of lamelac.
Adaptat1on of alls
many filaments covered with lots of lamellae proude alarge surtace area
sngle laye ot epthelad cells whch qive ashort ditfusion distance
cCuniercurrent flow along whoie gll mantans dofusion dradient and egulibrum
is never rached. Ditfusion gadient along length of lanela
fish nave a one way ventilation systen water flows over the gills.
water Is much denser than air so (sis difficult to move two
ways
more streamlned
wate support the qilh
