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AQA BIOL2 ~ 21 May 2012 ~ AS Biology

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    (Original post by QTpie118)
    I might be wrong, but don't insects have a LARGE surface area to volume ratio?
    yeah they do, anything small has large SA:V ratio - must've been a mistake
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    (Original post by QTpie118)
    I might be wrong, but don't insects have a LARGE surface area to volume ratio?
    Nah I was confused too - but the book mentions that it has a small surface area to volume ratio, and some other sites mention it. I'm not 100% but I'd go with what the book says >_<
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    How is heat loss related to oxygen uptake

    or how does less heat loss mean greater rate of respiration?
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    (Original post by wiwdhsdsd)
    Can anyone explain quick what apoplastic and symplastic pathway are ?
    symplastic pathway- water travels through living parts of the cell- cytoplasm. Cells diffuse by osmosis from one cell into another through the plasmodesmata.

    apoplastic pathway- water travels through non living parts of cell- cell wall. Water easily diffuses into the next cell by osmosis. Once the water gets to the layer of endodermis cells, its pathway is blocked by the casparian strip. This waxy strip forces water into the protoplast of the cell where it meets water from the symplastic pathway.

    The water is then actively transported into the xylem.
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    (Original post by Tikara)
    yeah they do, anything small has large SA:V ratio - must've been a mistake
    large compared to humans, small compared to bacteria
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    (Original post by Tikara)
    How is heat loss related to oxygen uptake

    or how does less heat loss mean greater rate of respiration?
    repiration releases heat.
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    (Original post by The Assassin)
    Nah I was confused too - but the book mentions that it has a small surface area to volume ratio, and I looked it up on google too.
    Oh right, well I think I'll just try and avoid mentioning it to be on the safe side.
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    Final 2 questions then im off. Thanks in advance

    How is tissue fluid formed

    How is tissue fluid removed
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    Yeah that's a good idea. Okay everyone I'm off to school. Good luck!
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    (Original post by QTpie118)
    I might be wrong, but don't insects have a LARGE surface area to volume ratio?
    Its all subjective, yes they have a small one compared to an amoeba, but compared to a human they have a large one, for the purpose of limiting water loss i'm sure you would get away with saying small V to SA ratio
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    I'm off to school now guys, good luck.
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    (Original post by Jack_Smith)
    I doubt ethical implication would be a 6 marker..i think it would be on insects on how plant leaves are adapted to efficient gas exchange
    how would u answer plant leaves efficient gas exchange please?
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    can someone make this clear please because i'm getting confused from notes
    does crossing over and independent assortment (segregation) happen in just meiosis or mitosis too? if in mitosis, how are the 2 daughter cells genetically identical if crossing over and independent assortment has occured to increase genetic variation?
    Also, which part of meiosis do they occur, 1 or 2 and stages? thanks!
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    (Original post by m rowe29)
    Its all subjective, yes they have a small one compared to an amoeba, but compared to a human they have a large one, for the purpose of limiting water loss i'm sure you would get away with saying small V to SA ratio
    Ohh, I get it
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    (Original post by xcristalx)
    can someone make this clear please because i'm getting confused from notes
    does crossing over and independent assortment (segregation) happen in just meiosis or mitosis too? if in mitosis, how are the 2 daughter cells genetically identical if crossing over and independent assortment has occured to increase genetic variation?
    Also, which part of meiosis do they occur, 1 or 2 and stages? thanks!
    Only meiosis.
    & Meiosis 1.
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    (Original post by nasira372)
    Final 2 questions then im off. Thanks in advance

    How is tissue fluid formed

    How is tissue fluid removed
    How tissue fluid is formed -

    Pressure in the capillary beds higher than the tissue fluid, hence fluid forced out of the capillaries and out into the spaces around the cells, which forms more tissue fluid.

    How its removed -

    Hydrostatic pressure in the capillaries reduces due to the loss of fluid, hence when blood reaches the venous there is a lower hydrostatic pressure inside the capillaries than the tissue fluid, hence tissue fluid forced back into capillaries.
    Also the lymphatic vessels get rid of the remaining tissue fluid.
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    HELP...how would you answer how plant leaves are adapted for efficient gas exchange?

    Thanks i'm really confused
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    (Original post by nasira372)
    Final 2 questions then im off. Thanks in advance

    How is tissue fluid formed

    How is tissue fluid removed
    High hydrostatic pressure in the arterioles pushes the tissue fluid out into the cell spaces. By the time the fluid returns, the hydrostatic pressure is greater on the outside of the arterioles and so the fluid returns inside. The proteins also reduce the W.P inside the arterioles thus water moves into the arterioles by osmosis.
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    (Original post by nasira372)
    Final 2 questions then im off. Thanks in advance

    How is tissue fluid formed

    How is tissue fluid removed
    Tissue fluid is just the oxygen, water, glucose and other small molecules that get pushed out of the capillaries due to the increased hydrostatic pressure inside the capillary. It is effectively just blood that bathes the tissues (don't write that in the exam).

    It is removed by increased hydrostatic pressure outside the capillaries that pushes the tissue fluid back into the capillaries and the lower water potential that will pull water back into the capillaries.

    Some tissue fluid may not get pushed into the capillaries and this excess fluid drains into the lymphatic system due to hydrostatic pressure differences
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    (Original post by xcristalx)
    can someone make this clear please because i'm getting confused from notes
    does crossing over and independent assortment (segregation) happen in just meiosis or mitosis too? if in mitosis, how are the 2 daughter cells genetically identical if crossing over and independent assortment has occured to increase genetic variation?
    Also, which part of meiosis do they occur, 1 or 2 and stages? thanks!
    Crossing over and independent segregation only happens in meiosis.
    Crossing over occurs when the homologous chromosomes line up (first stage). Independent segregation happens wen the chromosomes are pulled into different cells at the end of meiosis 1.

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Updated: January 15, 2013
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