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

  • View Poll Results: Are you resitting this unit?
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    Anyone have any tips on how to answer these questions? Questions in the exam I mean, I don't get what they're asking for and always say the wrong stuff.
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    (Original post by kingsmod1)
    jan 11 bio 2 was a disgusting paper lol
    That long question on shrimps was a joke, I had to stop.
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    Think an early night is in order tonight. Need to be well rested for max concentration so i can see through aqa's bull**** tommorow on this exam.
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    (Original post by parallal)
    Thanks. There was also a question in the June 2009 paper about circulation (the first question) and in the specimen paper.

    They weren't too bad but I hope it doesn't get any more complicated than those kinds of questions though.
    yeah, well ideally i would like a paper that hasnt got a lot of how science works questions, i prefer just knowledge based questions, im aiming for an A to push my grade to an overall A
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    Can someone explain these please:

    1. Transpiration Pull
    2. Root Pressure
    3. cohesion-tension hypothesis


    Thanks
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    My offer is 3 B's (i'm an a2 student) so hopefully i can get an A in this and never have to do it again. Biology is an interesting subject but AQA just make it horrifyingly painful.
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    (Original post by jbop)
    I'm the same, I waffle and think, yeahh that sounds reasonable. But if you miss out a key word that's your mark gone. I'm doing just that now, going through it with the mark scheme but it's all over the place! Have you seen 5cii and 5di? The answers are shocking! I had to check I was looking at the right mark scheme!
    yeah, the questions are really badly worded.but hey, what can we do! just gonna have to learn to try and read the examiner's mind :/
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    (Original post by Kandy_Kain_94)
    Can someone explain these please:

    1. Transpiration Pull
    2. Root Pressure
    3. cohesion-tension hypothesis


    Thanks
    Would be very nice :-)
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    (Original post by Kandy_Kain_94)
    Can someone explain these please:

    1. Transpiration Pull
    2. Root Pressure
    3. cohesion-tension hypothesis


    Thanks
    *Water is evaporated from the leaves, this creates a tension (or pull).
    *Water entering the xylem (through the root hair cell by osmosis) creates an upward push called root pressure.
    *Cohesive forces between the water molecules cause them to 'stick' together and form a column. And the water is pulled up as a column through the xylem.

    There's also adhesive forces between the walls of the xylem and the water molecules which pulls the walls of the xylem in as the column of water is moving up, which is why the stem/trunk of a plant/tree reduces in diameter during the day.
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    (Original post by James A)
    yeah, well ideally i would like a paper that hasnt got a lot of how science works questions, i prefer just knowledge based questions, im aiming for an A to push my grade to an overall A
    I absolutely hate HSW questions. Give me just recall questions and I'd pass this exam with flying colours.
    Good luck getting your A. I'm just trying to scrape a B. That stupid ISA really messed up my AS grade.
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    Do we need to know about myoglobin?
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    the jan 11 paper about Q how to calculate the cell cyle or sumfin like that, answer was 3, i was like wtf???

    jan 11 was disgusting lol

    any explanations?
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    (Original post by Kandy_Kain_94)
    Can someone explain these please:

    1. Transpiration Pull
    2. Root Pressure
    3. cohesion-tension hypothesis


    Thanks
    Transpirational pull is when water lost from mesophyl cells by evaporation into air spaces is replaced by water moving in from a neighbouring cell via osmosis along a water potential gradient. Water moves up the stem in the xylem due to root pressure and cohesion tension. Transpiration pull also occurs in the cohesion tension theory.

    Root pressure I believe is when the casparian strip in the endodermis prevents water moving alonng the apoplastic pathway and causes it to move along the symplastic pathway. Endodermal cells actively transport salts into the xylem. In order for water to then enter the xylem it must now be in the cytoplasm of the endodermal cells. The active transport of ions into the xylem lowers the water potential gradient and thus water moves into the xylem via osmosis along a water potential gradient. This creates a root pressure force, which helps to move water up a plant.

    The cohesion tension theory can be broken down into steps:-
    -water evaporates from the leaves of the plant due to transpiration
    -water molecules form hydrogen bonds between one another, sticking to each other know as cohesion
    -water forms a continuous, unbroken pathway across mesophyll cells and down the xylem
    -the column of water is drawn up due to the transpiration at the leaves
    -water molecules also stick to the inside of the xylem vessel know as adhesion
    -the entire column of water is pulled up the xylem vessel due to the tension put on the xylem by transpirational pull.
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    (Original post by mithunaa)
    Do we need to know about myoglobin?
    Not that I know of, I believe it's only haemoglobin
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    (Original post by Kandy_Kain_94)
    Can someone explain these please:

    1. Transpiration Pull
    2. Root Pressure
    3. cohesion-tension hypothesis


    Thanks

    Cohesion Tension theory:
    the cohesion part is the attraction between individual water molecules, caused by the hydrogen bonds between them. It causes 'surface tension' and the 'meniscus' on the surface of water and, in the xylem of plants, causes each water molecule in a xylem vessel to be attracted to its neighbours.
    Thus, if a water molecule is lost from the TOP of a plant, it will pull on its neighbour, which will pull on its neighbour, which wil....etc etc, all the way to the BOTTOM of the plant, where water will be attracted into a root hair.

    The TENSION part refers to the water being SUCKED up the plant, as aopposed to being PUSHED up the plant. The pressure inside each xylem vessel is thus negative (BUT positive inside the phloem, hence maple syrup and latex coming out when a tree is tapped), in just the same way as the pressure is negative inside a drinking straw when you suck.

    This is the opposite of the situation inside domestic water pipes, where the pressure is poitive and water squirts out when you nail through a pipe!

    So....water is lost from the leaves through evaoration,; it sucks water up the plant and the attraction between water molecules causes the water to be pulled all the way up the plant.
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    (Original post by parallal)
    I absolutely hate HSW questions. Give me just recall questions and I'd pass this exam with flying colours.
    Good luck getting your A. I'm just trying to scrape a B. That stupid ISA really messed up my AS grade.
    yeah thanks my isa i got a bang on B thats why im trying to make it up tommorow. well, anyhow i miss my biology and chemistry overall grades by a couple of marks off an A, i am not gonna be a happy bunny at all !

    good luck to you for tommorow !
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    hey don't know if this will help but this is what my teacher thinks will come up:

    Breathing rate in fish and insects
    DNA structure
    Mitosis
    Transpiration
    Cellulose
    Tissue Fluid and capillaries
    Antibiotic resistance
    Diversity and man's influence
    Classification

    This is just his predictions but most of what he predicted for january came up so you never know
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    (Original post by ScienceGeek3)
    Not that I know of, I believe it's only haemoglobin
    thanks!!
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    The paper's sooooo long though, I would say about 80% of things will come up.. :/

    Any predictions for the 6 marker?
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    Can someone simply explain immunological response as a way of comparing the relationship between species please? :]
 
 
 
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