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    (Original post by murtz14)
    Did anyone take this in January? Possibly the worst paper I've ever seen, pure dirt
    It was awful. Dirt is the right word
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    (Original post by Volltorb)
    Its the pollen in the peat bogs, the pollen comes form a certain species that live however long ago...By estimating the time it was released using carbon dating, it tell us how old it is and from which species it comes from. This specific species has certain ecological conditions that it grows in, which tells us what the weather may have been back then; all this helps determine what the weather was like.

    The pollen
    -outer coating is very resistant to decay
    -Dosnt grow/decay much if not at all in anaerobic and acidic conditions
    -Is abundant (in the ground/peat bogs), therfore easily obtained
    Thanks a lot!
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    (Original post by HQazi)
    It was awful. Dirt is the right word
    Its not the paper that's bad, it's the mark schemes! Too harsh and too specific!
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    Guys HELP please ,

    (b) The flow diagram below summarises some of the stages of phagocytosis, a
    non-specific response to a bacterial infection.
    (i) Identify D, E, F, G and H by writing appropriate terms in the spaces below.

    Bacteria with D on surface enter blood

    E produce F which bind to D and label
    Bacteria

    Labelled bacteria attach to F receptors
    on G

    G engulfs labelled bacteria by forming
    Vacuoles

    H is released into the vacuoles to
    destroy the bacteria
    (5)
    D ................................ ................................ ................................ ..................
    E ................................ ................................ ................................ ...................
    F ................................ ................................ ................................ ...................
    G ................................ ................................ ................................ ..................
    H ................................ ................................ ................................ ..................
    The mark scheme says the answers are : D=Antigens, E= plasma cells, F=antibodies, G=phagocyte and H= Lysozyme
    But aren’t plasma cells and antibodies involved in the specific response only?
    And isn’t H lysosome ?
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    [June 2011] Question 1(b) Name:  qq.jpg
Views: 303
Size:  102.1 KB

    (i) Suggest how these results could be displayed in order to compare the effect
    of temperature on the growth of seedlings of these two species. (3)

    My answer: Name:  r.jpg
Views: 286
Size:  53.6 KB
    - bar graph
    - x axis: temperature
    - y axis: change in mean dry mass
    - for each temperature draw 2 bars, one for each species, so the effect of temperature on mass can be compared for both.

    Mark scheme answer:
    1. reference to graph ;
    2. line (graph) / eq ;
    3. {Y / vertical} and {X / horizontal} axes correctly described. e.g. mass versus time / rate versus temperature ;
    4. idea of using same scale for axes (for both plants);
    5. idea of plotting each {temperature / species(plant)} separately ;

    Could someone explain if my graph is wrong? and how will the mark scheme graph help compare the two species?
    (do we have to say draw 2 line graphs, one for each species?)

    It's not a big question, but I would appreciate any help
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    (Original post by [email protected])
    Guys HELP please ,

    (b) The flow diagram below summarises some of the stages of phagocytosis, a
    non-specific response to a bacterial infection.
    (i) Identify D, E, F, G and H by writing appropriate terms in the spaces below.

    Spoiler:
    Show

    Bacteria with D on surface enter blood

    E produce F which bind to D and label
    Bacteria

    Labelled bacteria attach to F receptors
    on G

    G engulfs labelled bacteria by forming
    Vacuoles

    H is released into the vacuoles to
    destroy the bacteria
    (5)
    D ................................ ................................ ................................ ..................
    E ................................ ................................ ................................ ...................
    F ................................ ................................ ................................ ...................
    G ................................ ................................ ................................ ..................
    H ................................ ................................ ................................ ..................

    The mark scheme says the answers are : D=Antigens, E= plasma cells, F=antibodies, G=phagocyte and H= Lysozyme
    But aren’t plasma cells and antibodies involved in the specific response only?
    And isn’t H lysosome ?
    No, they can be involved in phagocytosis as well. Labelling done by antibodies help phagocytes detect and engulf pathogens faster.
    Lysosomes are organelles that contain hydrolytic enzymes (like lysozymes)
    These lysosomes fuse with vacuoles carrying the bacteria and release the lysozymes, which then digest the bacteria.
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    (Original post by Huntx)
    ****ing hell I have a clash between bio 4 and Eco 4. Mother****
    Same bro.... ****ing dreading it, "Judgement day" Buzzing for quarantine
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    can someone please explain me the difference between systematic and random sampling? like when to use which? and adv and disadv of each..please?
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    (Original post by SKK94)
    [June 2011] Question 1(b) Name:  qq.jpg
Views: 303
Size:  102.1 KB

    (i) Suggest how these results could be displayed in order to compare the effect
    of temperature on the growth of seedlings of these two species. (3)

    My answer: Name:  r.jpg
Views: 286
Size:  53.6 KB
    - bar graph
    - x axis: temperature
    - y axis: change in mean dry mass
    - for each temperature draw 2 bars, one for each species, so the effect of temperature on mass can be compared for both.

    Mark scheme answer:
    1. reference to graph ;
    2. line (graph) / eq ;
    3. {Y / vertical} and {X / horizontal} axes correctly described. e.g. mass versus time / rate versus temperature ;
    4. idea of using same scale for axes (for both plants);
    5. idea of plotting each {temperature / species(plant)} separately ;

    Could someone explain if my graph is wrong? and how will the mark scheme graph help compare the two species?
    (do we have to say draw 2 line graphs, one for each species?)

    It's not a big question, but I would appreciate any help


    you see, the question is about seeds which were grown for 50 days. which is a long period of time. A line graph is most suitable to use to show changes over time. I agree, we should use a bar graph for comparison. but here, we are carrying out the experiment in different temperatures, for 50 days. therefore, a line graph is more appropriate.


    Im not sure if u will get the marks for plotin a bar graph when they clearly ask for a line graph, but this is just me
    no, u have to draw 1 line graph for one species. then only u can compare between the 2 species. isn't it?

    can u please tell me which year's question is that
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    (Original post by iwantopas19)
    can someone please explain me the difference between systematic and random sampling? like when to use which? and adv and disadv of each..please?
    we use systematic sampling to measure the change in the distribution of a species in a particular area, there must be a continuous change in the gradient of the species across the area. for example, we want to measure the change across a habitat on a sea shore from high water mark to low water mark.

    random sampling is used to compare between two different areas. for example, we want to measure the abundance of a particular plant species in grazed and ungrazed area.
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    Whats the difference between an odema and inflamation, in terms of an inflammatory response. Is it one and the same thing?
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    one thing that really confuses me are the terms reliability, validity and accuracy, specially when they come on the same question.

    For example some question says comment on the reliability of (a certain given data set) comment on it's validity.

    How would a data set be accurate, reliable, valid?
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    (Original post by iwantopas19)
    you see, the question is about seeds which were grown for 50 days. which is a long period of time. A line graph is most suitable to use to show changes over time. I agree, we should use a bar graph for comparison. but here, we are carrying out the experiment in different temperatures, for 50 days. therefore, a line graph is more appropriate.


    Im not sure if u will get the marks for plotin a bar graph when they clearly ask for a line graph, but this is just me
    no, u have to draw 1 line graph for one species. then only u can compare between the 2 species. isn't it?

    can u please tell me which year's question is that
    Aha! Thanks Yeah, I guess I was just thinking too much.
    I plotted the bar graph so no one would get confused about my idea
    It's from Unit 4 June 2011
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    (Original post by Volltorb)
    Whats the difference between an odema and inflamation, in terms of an inflammatory response. Is it one and the same thing?
    I think an inflammation is the entire result of the iflammatory response, i.e redness of skin, increase in temperature and swelling;
    with the swelling itself being called an oedema.
    So I guess we can say that an oedema occurs during inflammation and that an inflammation is (overall) a non-specific response to infection?
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    (Original post by SKK94)
    I think an inflammation is the entire result of the iflammatory response, i.e redness of skin, increase in temperature and swelling;
    with the swelling itself being called an oedema.
    So I guess we can say that an oedema occurs during inflammation and that an inflammation is (overall) a non-specific response to infection?
    I see, thanks
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    Does anyone have january 2013 unit 4!!!! Cant find it anywhere!!
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    (Original post by bubblegummer)
    we use systematic sampling to measure the change in the distribution of a species in a particular area, there must be a continuous change in the gradient of the species across the area. for example, we want to measure the change across a habitat on a sea shore from high water mark to low water mark.

    random sampling is used to compare between two different areas. for example, we want to measure the abundance of a particular plant species in grazed and ungrazed area.


    thank u so much
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    (Original post by CONFUSED19)
    Does anyone have january 2013 unit 4!!!! Cant find it anywhere!!
    You can get it from the site free exam papers.
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    (Original post by abananapeel)
    one thing that really confuses me are the terms reliability, validity and accuracy, specially when they come on the same question.

    For example some question says comment on the reliability of (a certain given data set) comment on it's validity.

    How would a data set be accurate, reliable, valid?


    accuracy depends on the appratus u use.
    reliabitl
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    Anyone have the topic test answers of Hodder Edexcel A Level BIOLOGY for A2?
    Where can I get them?
 
 
 
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