Gas exchange
- Created by: elen roberts
- Created on: 21-05-13 17:48
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- Gas exchange
- SA to Vol. ratio
- Ficks law
- Rate of exchange depends on SA in contact with the surroundings
- SA/Vol.
- As organisms get bigger, SA:Vol gets smaller
- As organisms get bigger, exchange with surroundings gets harder
- Heat
- Small SA:Vol. ration slows heat loss, small organisms need high metabolism to generate more heat
- Insects
- Active, need to respire quickly
- Network of tubes carry air directly to cells from spiracels which lead to tubes called tracheae, which branch into tracheoles
- Trachioles are held open by chatin
- Oxygen and water diffuses in, CO2 diffuses out
- Trachioles can be ventilated using muscles to squeeze trachia
- Fish
- Gills
- Composed of filaments, covered by lamellae containing capillaries. Large SA, small distance
- Water flows over them so oxygen can diffuse in and Co2 can diffuse out
- Covered by muscular flaps - opercula
- Ventilation
- One way - through mouth, out opercular valves
- Inspiration
- Mouth opens and muscles contract lowering buccal cavity, increases volume and decreases pressure, outside pressure closes peculiar valves, water flows in
- Expiration
- Mouth closes and muscles relax raising buccal cavity, decreases volume, increases pressure, peculiar valves open, water flows out
- Counter Current flow
- Blood and water flow past each other in different directions, so diffusion is always occurring, giving 80% uptake
- Gills
- Plants
- Spongey mesophyll cells - irregular shaped, loosely packed spongey cells increase SA giving a large SA:Vol ratio
- Gasses enter through stomata surrounded by guard cells
- Water diffuses from xylem and mesophyll cells to air spaces in leaves
- Water loss
- Waterproof cutical made of lipids, moist air spaces, guard cells
- Adaptaions
- Paliside - thin cytoplasm, lots of chloroplasts
- Mesophyll cells - loosely packed, lots of space
- Photosynthasis increaces O2 in air spaces and decreces Co2, speeding diffussion
- SA to Vol. ratio
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