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    How would you answer the follwing

    list four ways in which the structure of a dicotyledonous leaf is adapted for gas exchange?
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    (Original post by The Smeezington)
    How would you answer the follwing

    list four ways in which the structure of a dicotyledonous leaf is adapted for gas exchange?
    i dont they will ask for four ways a leaf is adapted for GAS EXCHANGE. is there even four ways it is adapted?
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    (Original post by The Smeezington)
    How would you answer the follwing

    list four ways in which the structure of a dicotyledonous leaf is adapted for gas exchange?
    1. transparent upper epidermis-lets light through
    2. palisade layer underneath-consists of thin. long and tightly packed cells containing lots of cholorplast & chlorophyll
    3. loosely packed spongy mesophyll layer- has many air spaces 2 allow circulation of gases
    4.lower epidermis has pores called stomata-allow gases 2 be exchanged between leaf and outside air.
    5. stomata have TWO GUARD CELLS that can swell 2 open the pore, when the guard cells are not turgid then stoma closes
    6. leaf vein system-contains xylem & phloem tissues 2 transport water in2 leaf and assimilates to other part.
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    (Original post by pastpaper-guy)
    i dont they will ask for four ways a leaf is adapted for GAS EXCHANGE. is there even four ways it is adapted?
    lol yeah there are plenty of points
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    (Original post by anonymous_angel_16)
    I don't think you can ever be ready for a test but this one I am seriously not ready for!
    Just had a panic attack feeling I don't know anything!
    I blame my maths exam - I was concentrating on that
    but yh, hope i do well. Good luck! and judging from your posts, I really don't think you'll get an E - you'll do a lot better
    yeaahhh that was copied from my notes.
    But seriously, tomorrow better run smooothly or i will kick up a fuss with OCR.
    GOOD LUCK FOR TOMORROW !!
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    Right guys im struggling with HOW TO ANSWER something.. I fully understand the concept but I cringe when I see this question 'cos i get the wording wrong.. its quite simple..

    Something like why a multi cellular organism needs a transport/circulatory system?

    Why a multi cellular organism needs specialised exchange surface?

    I mean HOW do you answer this and whats the difference? Please anyone?
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    (Original post by 786girl)
    lol yeah there are plenty of points
    daymm. better revise that bit then lol
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    (Original post by Rosi M)
    Right guys im struggling with HOW TO ANSWER something.. I fully understand the concept but I cringe when I see this question 'cos i get the wording wrong.. its quite simple..

    Something like why a multi cellular organism needs a transport/circulatory system?

    Why a multi cellular organism needs specialised exchange surface?

    I mean HOW do you answer this and whats the difference? Please anyone?
    have you consulted the mark scheme for the answers?
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    (Original post by Rosi M)
    Right guys im struggling with HOW TO ANSWER something.. I fully understand the concept but I cringe when I see this question 'cos i get the wording wrong.. its quite simple..

    Something like why a multi cellular organism needs a transport/circulatory system?

    Why a multi cellular organism needs specialised exchange surface?

    I mean HOW do you answer this and whats the difference? Please anyone?

    a multicellular organism requires alot of oxygen to be able to respire. diffusion alone is insufficient for the needs of the organism so has a gas exchange transport system which would supply sufficient oxygen to the cells.
    some organisms have a large surface area to volume ratio meaning diffusion will not get to all parts of the organism, thus requiring a transport system.

    closed ciculatory systems are something else. that just means the blood is in vessels.
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    (Original post by The Smeezington)
    Why is there always so little on the heart when it's the area i'm best at.
    Might be the year then. I never used to be able to do the heart and the cardiac cycle and couldn't for the first time however now I can do the cardiac cycle. But if there was, I wouldn't want there to be anything about electrocardiograms as I can never remember what each of the letters is.
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    (Original post by Rosi M)
    Right guys im struggling with HOW TO ANSWER something.. I fully understand the concept but I cringe when I see this question 'cos i get the wording wrong.. its quite simple..

    Something like why a multi cellular organism needs a transport/circulatory system?

    Why a multi cellular organism needs specialised exchange surface?

    I mean HOW do you answer this and whats the difference? Please anyone?
    Why a multi cellular organism needs specialised exchange surface?

    well, because;
    -they need 2 remove waste products eg co2 (in animals) o2 (in plants) urea etc
    -single celled need it coz they can exchange gases, nutrients &wastes across their outer surfaces-they have a LARGE SA;V

    larger organisms need it bcoz they need it for oxygen for respiration. they cannot supply enough through their skin surface as theyhave a SMALL SA;V.
    a special surface area 4 exchange gives a greater area so more o2 can be absorbed and more co2 can be removed.
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    (Original post by pastpaper-guy)
    a multicellular organism requires alot of oxygen to be able to respire. diffusion alone is insufficient for the needs of the organism so has a gas exchange transport system which would supply sufficient oxygen to the cells.
    some organisms have a large surface area to volume ratio meaning diffusion will not get to all parts of the organism, thus requiring a transport system.

    closed ciculatory systems are something else. that just means the blood is in vessels.
    Right thanks for that So basically large SA:V, more oxygen/nutrients needed, diffusion not enough to meet needs so gas exchange system. ok
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    (Original post by pastpaper-guy)
    daymm. better revise that bit then lol
    haha me too, didnt realise we had to learn it! thankfully its kindof straightforward

    (Original post by Rosi M)
    Right guys im struggling with HOW TO ANSWER something.. I fully understand the concept but I cringe when I see this question 'cos i get the wording wrong.. its quite simple..

    Something like why a multi cellular organism needs a transport/circulatory system?

    Why a multi cellular organism needs specialised exchange surface?

    I mean HOW do you answer this and whats the difference? Please anyone?
    i think its pretty much the same concept for both,
    large organisms have a small SA:vol so direct diffusion from environment to cells to supply the organism with the nutrients etc it needs and remove the waste products at the rate it needs to maintain a safe level, is not feasible/inefficient compared to smaller organisms (for which gases etc can simply diffuse directly through their plasma membranes). also multicellular organisms are a larger size therefore some cells are too deep inside and not exposed to the environment directly for diffusion in this way. plus active organisms have a higher demand for O2 and to remove CO2 (high respiration rate) and so need a specialised exchange surface/transport system.

    i think its basically to do with diffusion being too slow to supply needs regarding SA:Vol, size, and activity levels. but i know exactly what you mean about losing marks so easily for the right answer but just not the exact specific words they want


    edit... Sorry didnt realise replies had already come in!
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    hey can anyone xplain transpiration 2 me....i still dont get it :confused:
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    (Original post by Jhyzone)
    have you consulted the mark scheme for the answers?
    I am now
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    (Original post by giraffegiraffe)
    haha me too, didnt realise we had to learn it! thankfully its kindof straightforward



    i think its pretty much the same concept for both,
    large organisms have a small SA:vol so direct diffusion from environment to cells to supply the organism with the nutrients etc it needs and remove the waste products at the rate it needs to maintain a safe level, is not feasible/inefficient compared to smaller organisms (for which gases etc can simply diffuse directly through their plasma membranes). also multicellular organisms are a larger size therefore some cells are too deep inside and not exposed to the environment directly for diffusion in this way. plus active organisms have a higher demand for O2 and to remove CO2 (high respiration rate) and so need a specialised exchange surface/transport system.

    i think its basically to do with diffusion being too slow to supply needs regarding SA:Vol, size, and activity levels. but i know exactly what you mean about losing marks so easily for the right answer but just not the exact specific words they want
    Thanks Yeah I know.. I've literally memorised mark schemes for translocation/transpiration etc. They are unbelievably fussy!
    (Original post by 786girl)
    Why a multi cellular organism needs specialised exchange surface?

    well, because;
    -they need 2 remove waste products eg co2 (in animals) o2 (in plants) urea etc
    -single celled need it coz they can exchange gases, nutrients &wastes across their outer surfaces-they have a LARGE SA;V

    larger organisms need it bcoz they need it for oxygen for respiration. they cannot supply enough through their skin surface as theyhave a SMALL SA;V.
    a special surface area 4 exchange gives a greater area so more o2 can be absorbed and more co2 can be removed.
    Thanks for that xx
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    my arse hurts after all this revision.
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    (Original post by rasklatz)
    my arse hurts after all this revision.
    lol revise in bed then.
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    (Original post by fahimak)
    hey can anyone xplain transpiration 2 me....i still dont get it :confused:
    do you mean the whole thing about how water moves up the stem or do u mean things like the factors that affect transpiration and potomotre and about xerophytes?


    transpiration; loss of water by evaporation from the aerial parts of a plant
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    (Original post by fahimak)
    hey can anyone xplain transpiration 2 me....i still dont get it :confused:
    Which part of transpiration? There's a few parts to it thats why
 
 
 
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