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AQA BIOL2 Biology Unit 2 Exam - 26th May 2011 watch

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    (Original post by al_habib)
    In general what do we need to know about the variation topic..Tx alot
    measure diameteter of the lumen, in mm which is 25/8 = 3.125
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    (Original post by mclovin123)
    spricles are insectes not plants. But yes talk about waxy waterproff cuticles. talk about curtain xerophytic adaptations such as stoamata in pits which traps moist humid air, this reduces the concentration gradient of water. hairs trap moist humid air and also reduce the concentration gradient of water. Also talk about maybe how guard cells are turgid (open stomata) when hydrated and how they are flaccid (close stomata) when dehydrated and relate this, the fact the stoma are closed reduces h20 loss.
    Thanks for that! And yes I was talking about insects.

    (Original post by emillie)
    Am I right in thinking we don't need to know how to work out standard deviation?
    Yep.
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    (Original post by Twigleheight)
    Magnification = Image / Object
    so..
    Object = Image / Magnification

    You then just put the numbers into the equation and there's the answer
    How do we convert mm in Um?
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    (Original post by Master.K)
    How do we convert mm in Um?
    Multiply mm by 1000 to get um.
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    (Original post by Master.K)
    Thanks for that! And yes I was talking about insects.



    Yep.
    LOOl yeh sorry i sounded like a bit of a **** but yeh i would also mention about spiricles, then teacheae, which lead to trachioles, which are thin and run off right onto cells so the oxygen goes down the concenrtration gradient to the cells
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    (Original post by mclovin123)
    LOOl yeh sorry i sounded like a bit of a **** but yeh i would also mention about spiricles, then teacheae, which lead to trachioles, which are thin and run off right onto cells so the oxygen goes down the concenrtration gradient to the cells
    sorry what do you mean by O2 goes down the concentration gradient is it by diffusion
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    (Original post by mclovin123)
    no idea, my teacher mantioned it but sheis stupid so dunno. I doubt we would but im scared
    Not standard deviation as it tells you in the textbook that we dont need to know it for the exam only for the ISA. However know how to do index of diversity calculations and they usually ask "explain why it may be more useful to calculate the index of diverity than to record the number of species present 2 marks"
    answer is " measures no. of individulas and number of species and some species only present in some no.
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    (Original post by al_habib)
    sorry what do you mean by O2 goes down the concentration gradient is it by diffusion
    no its not. Basicly. Oxygen inters the insect through the spiricles. It then goes through the thecheae, these tracheae run off into smaller pipes called trachioles. These thrachioles literraly just run straght onto cells. They are thin and so oxy then diffuses from them into the cells. If you think about it in a simple way it will make sense. Their is more oxygen outside then in the insect so the H2 will move through these pipes down the concentration gradient, and c02 goes down its concetration gradient from the cells up these pipes and out of the spiricles.
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    (Original post by Master.K)
    Ok so just like sayin water proof coverings/spiracle are opened and closed by valves etc?
    Aye and they also have a small surface area to volume ratio to minimise the area over which water is lost.
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    (Original post by Some random guy)
    Aye and they also have a small surface area to volume ratio to minimise the area over which water is lost.
    plus a waxu cuticle and tiny hairs which prevent evaporation
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    (Original post by Master.K)
    How do we convert mm in Um?
    Thanks.
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    Is the transpiration pull when water is pulled up the column?
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    OK, does anyone actually know what the UMS system is all about? I was under the impression that 80%, 65/85, was the lowest mark that you can get to get an A? but from what people are saying here, it seems like its actually a lot lower? I dont understand the AQA UMS converter thing either, i got 78% in my january unit 1, and got a B, so i re-sat it last week, but Ive done past unit 2 papers and the converter says that my marks, that range between 64 and 73 out of 85 are all As?

    SOMEONE HELP?!
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    (Original post by mclovin123)
    plus a waxu cuticle and tiny hairs which prevent evaporation
    We're talking about insects dude :P
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    could someone summarise the stuff we need to know about cell differentiation pleease.
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    (Original post by Master.K)
    Is the transpiration pull when water is pulled up the column?
    transpiration pull? normally its called cohesion tension, if ive understood what youre trying to say.

    if you are talking about cohesion tension, then yes, the hydrogen bonds between the water molecules mean that when water evaporates from the stomata and the surface of the leaf, the water in the xylem - as long as it is a continuous column, will be pulled up. (with a little help from root pressure too!)
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    (Original post by al_habib)
    could someone summarise the stuff we need to know about cell differentiation pleease.
    Just the definitions of organ,tissue and specilisation.
    And the three systems:
    The circularity system
    The exchange system
    The digestive system
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    (Original post by al_habib)
    could someone summarise the stuff we need to know about cell differentiation pleease.
    i was under the impression that its quite a small part of the syllabus, and theres not much to know,

    basically, that cells are specialised, such as muscle cells, and these specialised cells group together to form tissues. similar tissues are grouped as organs, and then organs with similar functions are grouped as systems.

    a really popular question is 'what is a tissue?' all you need to say is that tissues are groups of similar cells. another is 'what is an organ?' and the answer is basically the same but with *tissues* instead of cells.
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    Anyone have an inkling of what the big questions on the back could be on???
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    (Original post by Some random guy)
    We're talking about insects dude :P
    Yes insects have a outer waxy cuticle and tiny hairs over their body which reduces evsporation. Unless the cgp book is wrong :confused:
 
 
 
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