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    (Original post by Hmb28)
    1pm like everyone else's
    Mine starts at 1.30pm
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    The chi squared test isn't in any of the text books I have (CGP and the OCR Year 1 and AS Biology). I don't think it comes up in AS. The only tests we've been told are, Standard Deviation, T test, and Spearman's rank correlation coefficient.
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    (Original post by MattLS)
    The chi squared test isn't in any of the text books I have (CGP and the OCR Year 1 and AS Biology). I don't think it comes up in AS. The only tests we've been told are, Standard Deviation, T test, and Spearman's rank correlation coefficient.
    OCR published resources on it last week, make of that what you will.
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    (Original post by plower)
    Roots- there are two routes: The apoplast pathway where water goes through the cell walls, mostly by diffusion, until it reaches the endodermis cells in root where the path is blocked by a waxy strip called casparian strip, so now it has to go through the Symplast pathway where the water goes through the cytoplasm via osmosis, plasmodesmata connects connects the cytoplasm of plant cells.

    Leaves: the water leaves the xylem and moves into the cell mainly by apoplast where it evaporates into the air spaces in the leaf. When the stomata is open, it diffuses out.

    Stem: as the water is evaporated, this creates a 'tension' where which pulls more water upwards. Water molecules are cohesive so a whole column of whole water moves too. Also adhesion is partly involved as well since the water molecules are attracted to the walls of xylem vessel, it helps water rise up.

    Good luck xo
    THANK YOU SO MUCH , good luck to you all
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    what PAAGs have you all done, we have done heart disection, light microscope , beetroot and benedicts test for sugars :/
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    Yooooo have you guys learned of the inorganic ions and it's purpose???
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    has anyone studied inorganic and organic ions?
    apart of biollogical molecules
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    Whats selective pressure
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    Can someone please explain cell mediated immunity? 😢
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    (Original post by asdfghjkl99)
    Whats selective pressure
    Selective pressure are like environment factors, eg predation, disease, competition etc which creates a struggle for survival.

    (Original post by Wonder_land)
    Can someone please explain cell mediated immunity? 😢

    Cell mediated is where T-cells come in, they surface covered with receptors that binds to antigens presented by antigen-presenting cell (phagocyte). Each t-cell has different receptor due to the complimentary antigens. When it binds to one, it activates t-cell where it undergoes clonal explansion- divides producing clones which differentiate into different types: such as T helper cell- release substance to activate B cell, T killer cell that binds to antigen and kills pathogen, T regulatory cell that suppresses immune response from other white blood cell to stop mistakenly attack host body cell and lastly Memory T cells
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    (Original post by Wonder_land)
    Can someone please explain cell mediated immunity? 😢
    Cell mediated immunity is the immune response to cells that have undergone changes (such as by a virus infection).

    Macrophages digest the pathogen by phagocytosis. The antigens from the pathogen combine with glycoproteins in the cytoplasm of the macrophage called the major histocompatibility complex (MHC). The cell then presents these antigens on its own cell-surface membrane and becomes and antigen-presenting cell (APC).

    The production of the APC stimulates T-helper cells (due to complementary cell-receptors on its membrane to the antigens) to produce interlukin-1, which in turn stimulates the production of interlukin-2. This induces the rapid division and differentiation of the T-helper cell into T-killer cells or T-memory cells. The T-helper cells produce the protein perforin which causes the formation of pores in pathogens and thus, lysis. T-memory cells give rapid response if the pathogen invades the body again.
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    i havent learnt inorganic ions
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    does everyone know the gas exchange in bony fish and insects?
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    What are the diseases i need to know ? what kind type are they? eg- virus or bacteria
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    (Original post by fteam)
    does everyone know the gas exchange in bony fish and insects?
    I wont go into too much detail cos im rushing to school butbCounter current system in fish -blood travels opposite way to water coming in and oxygen diffused in water diffuses into fish and concentration gradient of o2 is greater than concentration in blood..pretty much that but not in loads of detail as said..

    Insect -o2- spiracles - treacheae - tracheoles whilst co2 moves down its own cg towards spiracles..o2 diffueses inyt fluid in tracheoled ehich is drawn by osmosis later on leaving o2 which directly diffuses into respiring cells
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    (Original post by sugi10)
    What are the diseases i need to know ? what kind type are they? eg- virus or bacteria
    Bacteria..tb bacterial meningitias ringrot
    Virus - hiv influenza toabacoo mosaic
    Fungi - athletes foot ring worm black sigatoka
    Protoctist - malaria and potato late blight
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    Cell mediated immunity is to do with antigens processed inside cells. T helpers will bind their receptors to an antigen on an apc, they will then secrete interlukins to stimulate growth of t helpers, t memory and b plasma lymphocytes.
    This is from memory so may have some inaccuracies.
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    (Original post by sugi10)
    What are the diseases i need to know ? what kind type are they? eg- virus or bacteria
    VIRUS:
    - Tobacco Mosaic (Plants)
    - HIV and Influenza (Humans)

    BACTERIA:
    - Bacterial Meningitis (Humans)
    - Ring Rot (Plants)

    PROTOCTISTA:
    - Late Blight (Plants)
    - Malaria (Humans)

    FUNGI:
    - Athletes Foot
    - Black Sigatoka
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    Can someone please explain Benedicts test as I don't have a ****ing clue
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    (Original post by Gogregg)
    Yes, we do need to know it! You'll get the formula, but we need to work out observed - expected and square it then do some other stuff and compare answer to the critical value at p=0.05.Observed value is using your null hypothesis (there will be no difference) so your saying there will be the same number for each testWishing everyone the best of luck today!
    Another thing to learn Teachers have only told us about Simpson's index, standard deviation and student's t-test. :grumble:

    (Original post by James3000117)
    You're thinking of the Hardy-Weinberg principle. Gregg explajns chi squared well, just remember when subbing in that fO is observed values and fE is expected values and you should be able to work from there.
    Do you have a link to a good website or something to learn it?
 
 
 
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