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    TheBioTutor is a great website everyone - he has put past papers in topics and other useful resources
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    (Original post by rich*****)
    because i literally know nothing as i've been busy watching tv for 5 days in a hospital and i finally got out! I'll do an allnighter, after all it is my last and final exam!!!!!
    Does anyone have any tips and resources i could use please it's urgent!!!!


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    aha! Me too!!!
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    (Original post by shalalondon)
    Difference between locus and linkage please? Anybody??
    Locus - the location of a gene on its chromosome

    Sex linkage (I presume) is all about genes on the sex chromosomes - X and Y. The main things to remember are the case studies of haemophilia and colour blindness, and how men are far more likely to get them than women, since the only copy of the associated genes exists on the X chromosome. For example, haemophilia is caused by a recessive allele, but since there's nothing on the Y chromosome, it will always be expressed.
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    What do we need to know about Galapagos island?
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    OCR biology past papers are just about the most irrelevant things to use to revise

    There is no continuity between papers and they change the paper a lot between exam seasons

    If you do them, do them to familiarise yourself with dodgy OCR wording but don't use them as your sole source of last minute revision
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    (Original post by Saltedcaramel1)
    Yaaas, it's pretty simple and it hasn't come up in forever so pretty good chance it will tomorrow
    Came up in jan 2013


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    can anyone explain to me the 2 ways of defining a species ?
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    Anyone made predictions on here or not?
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    Biological species concept - group of organisms of the same species that can interbreed with one another and produce a fertile offspring
    Phylogenetic species concept - group of organisms that are sharing the same morphology, physiology and occupy the same niche
    (Original post by TheLegalDealer)
    can anyone explain to me the 2 ways of defining a species ?
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    (Original post by MiniSlash)
    Correct me if I'm wrong, this is a summary of the main roles of these hormones (off the top of my head)

    Plant Hormones:
    Auxin
    - Apical dominance

    Gibberellin
    - Cell elongation

    Abscissic acid
    - Stimulates the production of 'ethene'

    Ethene
    - Fruit ripening and leaf abscission

    Auxins are used in rooting powder
    Auxins can be used as weedkillers

    I know of some kind of abscissic acid (unanamed in my revision guide) that is an anti-transiprant; stops transpiration by closing Stomata

    If you chop off the tip of a plant lateral/axillary buds grow, since there's no more apical dominance.

    Regarding tropisms...

    Phototropism = light
    Geotropism = gravity
    Thigmotropism = touch

    Positive tropism = toward stimulus
    Negative tropism = away from stimulus

    Phototropism
    Auxins accumulates on the shaded side of the plant, these cells take up more water and elongate lengthways - they are somehow structured so that they don't widen, but lengthen.

    I hope this helps
    thank you very much this is great
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    (Original post by Student23478)
    Has anyone got a link to the old past papers??
    how old
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    (Original post by TheLegalDealer)
    can anyone explain to me the 2 ways of defining a species ?
    There's the biological species concept which states that a species are a group of organisms that are able to reproduce fertile offspring.

    The problems with the biological species concept is that it can be hard to see what species a newly discovered organism belongs to because their reproductive behaviour may be unable to be measured. For instance, if the organism reproduces asexually, species is now extinct, ethical/practical issues.

    So most scientists use the phylogenetic concept which looks at the history of an organism. Looking at what it is related to and how closely.
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    http://us22.chatzy.com/94903706046868 join us on this chat if you want to do some revision and help each other
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    (Original post by peanutcracker20)
    thank you very much this is great
    Don't mention it! Explaining it to others helps me with my own revision, so it's a win win.
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    What are the predictions for this years paper?
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    Why are there so many questions asking about how you'd carry out an experiment? IS this a proper thing as my teacher said absolutely nothing about this
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    Anybody have any questions they want answered?
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    (Original post by tewas)
    Anybody have any questions they want answered?
    Do you understand all that shiz about monopyletic, paraphyletic, haplotypes, clades, taxa and all that shiz :sigh::mad:

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    I need to destroy this paper for my A but I dont think its gonna happen.
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    How much genetics stuff will come up?
 
 
 
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