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    hi, i was wondering does anyone know of an official AQA chemistry thread for the unit 5 exam this year? cant seem to find it....
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    (Original post by HELPME-ology)
    Does anyone have good material or revision notes they used for the Immune system and disease etc?

    thats for the Biology OCR June AS exam.. pleaseeeeeee help me!!!!!!!!

    the people who re-sat this paper in Jan 2010 said it was mainly all Biochemistry.. so i have a feeling all the immune system and disease is to definitely come up..
    might have some on my school VLE, pm me your email, will lookee-see and if so will email any- and everything i find
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    Hey can anyone help me on the control of body plan development??
    Im a bit confused - are homeobox genes and homeotic genes the same? I have two textbooks that call them different things but seem to have the same function...
    Homeotic genes code for the proteins needed to control body plan development. The homeotic genes have regions called homeobox sequences that code for the homeodomain (which is part of the protein). The homeodomain binds to specific sites on the DNA which allows the protein to work as a transcription factor, which are located at the start of developmental genes, activating or repressing transcription which alters the production of proteins involved in the development of body plans.
    is that right at all??
    also Im not sure where hox clusters fit into it all - all I know is that the homeobox genes (are these homeotic genes??) are arranged in hox clusters...
    thanks!
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    (Original post by Liverpool F.C.™)
    Here
    Thank you!!
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    (Original post by Sakujo)
    describe how the distribution and abundance of organisms can be measured, using line transects, belt transects, quadrats and point quadrats (HSW3);

    I'd rep if someone does this.
    Ok, you can take samples within a habitat in order to determine the abundance/distirbution of a particular species, and then you see if this is determined by other species or environmental factors such as light or nitrates in the soil. e.g. There may type of one plant growing in the light, but lots more of another species in the shade.

    Ideally, it would be best to count all the individuals in the habitat, but this is not possible so samples are taken. There are various methods of taking samples:

    1) Quadrats- these are square frames 1m by 1m that define the sample space, they have string inside the frame separating the square into 100 smaller squares. You can either find out the distribution of a species by counting the presence/absence of them in the quadrat or you can estimate the abundance by taking a percentage cover estimate.

    You can do this just with a quadrat but taking a % coverage is more acurate using a point frame/quadrat.

    You point the frame into the ground within the quadrat, and record the species that are touching each of the pins, this is representive of the cover.
    There are 10 pins on each frame and this can be repeated 10 times in a quadrat.

    2) Transects- these are lines taken across a habitat and you record the samples along the line at regular intervals.
    You can use this in association with a quadrat, whereby you place a quadrat by the line at intervals and use that to measure abundance/percentage cover. This is called a belt transect.
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    (Original post by dopeyangel101)
    might have some on my school VLE, pm me your email, will lookee-see and if so will email any- and everything i find
    anything yet about the genetics questions ? done the rest, just waiting for genetics now.
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    i'll see what i can do tomorrow, shall attempt to use my scanner at home, if not will take photos of each page then upload them. sorry i havent done it yet, have honestly been too busy revising for chemistry....
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    Genetics pack mark scheme.doc

    Genetics pack-1.doc

    Genetics questions and mark schemes for those who want it, uer23.

    EDIT: Fixed
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    (Original post by Sakujo)
    Attachment 85826

    Genetics pack mark scheme.doc

    Genetics questions and mark schemes for those who want it, uer23.
    the actual questions dont work on my computer, comes up with a load of random numbers and letters...
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    (Original post by Sakujo)
    Attachment 85826

    Genetics pack mark scheme.doc

    Genetics questions and mark schemes for those who want it, uer23.
    Hey brother thanks a lot Do you more of these question packs, like the ones you did for chem ?
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    (Original post by dopeyangel101)
    the actual questions dont work on my computer, comes up with a load of random numbers and letters...
    Should be fixed for some reason the document was in rtf format not doc
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    (Original post by Liverpool F.C.™)
    Hey brother thanks a lot Do you more of these question packs, like the ones you did for chem ?
    My humble apologies bro but I don't, I really wished I did though. :sigh:
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    (Original post by Sakujo)
    Should be fixed for some reason the document was in rtf format not doc
    thanks, tis sorted now

    saved me a lot of hassle too
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    Thank ViolinGirl.

    Right, what does niche mean in this sentence?

    'The more niches overlap, the more likely competition will occur.'
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    (Original post by zoop)
    Thank ViolinGirl.

    Right, what does niche mean in this sentence?

    'The more niches overlap, the more likely competition will occur.'
    No problem. Please ask away

    Well, the niche is the role an organism plays in its ecosystem, this can include what it feeds on, what it excretes, how it reproduces.

    Some niches of different species can be similar, but they are never identical, as it just isn't possible.

    So the more similar the niches are, it means that the organisms are more likely to comptete with one another, as for example they may share the same food sources, so will have to comptete over this. One species may be better adapted at harvesting that food source, they will be the species that thrives while the other one has more of a struggle to survive.
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    (Original post by ViolinGirl)
    No problem. Please ask away

    Well, the niche is the role an organism plays in its ecosystem, this can include what it feeds on, what it excretes, how it reproduces.

    Some niches of different species can be similar, but they are never identical, as it just isn't possible.

    So the more similar the niches are, it means that the organisms are more likely to comptete with one another, as for example they may share the same food sources, so will have to comptete over this. One species may be better adapted at harvesting that food source, they will be the species that thrives while the other one has more of a struggle to survive.
    Aha my typing is appalling!! Thanks again, completely get it now. Man u'll ace this easily! How do u revise if u don't write any notes? U seem to know it all real well! U're off for vet med too aren't u? Where are ya going?

    Would + rep you but can't for another 28 days app :o:
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    (Original post by ViolinGirl)
    No problem. Please ask away

    Well, the niche is the role an organism plays in its ecosystem, this can include what it feeds on, what it excretes, how it reproduces.

    Some niches of different species can be similar, but they are never identical, as it just isn't possible.

    So the more similar the niches are, it means that the organisms are more likely to comptete with one another, as for example they may share the same food sources, so will have to comptete over this. One species may be better adapted at harvesting that food source, they will be the species that thrives while the other one has more of a struggle to survive.
    thanks that explains a lot
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    (Original post by Sakujo)
    Genetics pack mark scheme.doc

    Genetics pack-1.doc

    Genetics questions and mark schemes for those who want it, uer23.

    EDIT: Fixed
    I don't get 2 iii. Help please.
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    (Original post by Sakujo)
    Genetics pack mark scheme.doc

    Genetics pack-1.doc

    Genetics questions and mark schemes for those who want it, uer23.

    EDIT: Fixed
    do you have any of these for the other topics besides genetics?
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    (Original post by ViolinGirl)
    I don't get 2 iii. Help please.
    I don't get it either these questions are a step up from A-level/off the sylabus in some cases.
 
 
 
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