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AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011 Watch

  • View Poll Results: Are you resitting this unit?
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    (Original post by choc1234)
    what is the purpose of the blind spot?
    Evolutionary fault ? :confused:
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    (Original post by choc1234)
    what is the purpose of the blind spot?
    It doesn't have a purpose as such.

    It doesn't have any rods or cones as it is the place where the optic nerve connects to the retina.
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    (Original post by choc1234)
    what is the purpose of the blind spot?
    Its where the optic nerve leaves at the back of the eye, so there are no photoreceptors there
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    (Original post by laura123)
    Yeah! I saw that yesterday! I reckon it's a mistake in the mark scheme, cause all the text books say it's the movement of potassium ions out of the axon that causes repolarisation.

    ohh i think they are talking about the sodium potassium pump...
    like 3 sodium ions go out for every 2 K+ that comes into the axon...this establishes resting potential.
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    (Original post by choc1234)
    insert a gene into what?
    Stem cells. And as they replicate they keep making the gene unlike body cells that die.
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    (Original post by Phalange)
    1) Chemoreceptors are found in medulla, aorta and cartoid artery. Say the chemoreceptor in aorta detected high CO2, low O2 and low pH. It would send impulse via sensory neurone to medulla to decide what to do. What would happen if the medulla detected the high CO2 etc? Would it "skip" the sensory neurone part or...?

    2) IAA inhibits growth in roots but stimulates growth in tips right? Wouldn't gravity cause IAA to accumulate at the tip of the root causing it to stop growing downwards? Unless the root growing region is NOT the tip? :|

    Thanks if anyone can help! Quote me
    hmm i thought that IAA causes a decrease in growth in root cells so if you place a root hoizontally there will be a high concentration of IAA on the lower surface aand so cell elongation will cause the root to bend down towards gravity instead of up (which it would if IAA stimulated the growth of root cells as it does in shoot cells)
    not sure myself tbh
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    blind spot is just a disadvantage where there are no photoreceptors....


    lol just saw im just repeating what u guys said! ;D
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    I'm just going to leave all the unit 5 stuff for now and focus on the essay. May aim is to get x>18.
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    (Original post by Jin3011)
    I'm just going to leave all the unit 5 stuff for now and focus on the essay. May aim is to get x>18.
    How do you plan on getting good marks on the Scientific content bit, focus on 4 topics and go into detail?
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    (Original post by choc1234)
    hmm i thought that IAA causes a decrease in growth in root cells so if you place a root hoizontally there will be a high concentration of IAA on the lower surface aand so cell elongation will cause the root to bend down towards gravity instead of up (which it would if IAA stimulated the growth of root cells as it does in shoot cells)
    not sure myself tbh

    Related question: How does IAA inhibt root growth? I mean in the CGP, it says it inhibts, and then it says it causes it to bend...but if its bending, isn't it growing?

    Please help, getting a bit panicy now
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    (Original post by choc1234)
    what is the purpose of the blind spot?
    The blind spot is created by the area where the optic nerve connects to the retina. You can't have cones, rods, bipolar neurons etc. if the optic nerve is there. Unfortunate, but it is evolutionarily necessary!
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    i dont know why but seeing all these comments have made me realise how unprepared i really am lol..
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    (Original post by NRican)
    How do you plan on getting good marks on the Scientific content bit, focus on 4 topics and go into detail?
    Not sure, I'll just try to get a logical sequence in my head and then start writing about relevant things to the question. Under pressure, I'm really bad at essayst'is the reason I left psychology behind at AS.
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    (Original post by Jin3011)
    I'm just going to leave all the unit 5 stuff for now and focus on the essay. May aim is to get x>18.
    hey best of luck
    nd make sure u get some sleep
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    (Original post by Jin3011)
    I'm just going to leave all the unit 5 stuff for now and focus on the essay. May aim is to get x>18.
    how are you going to revise for the essay?
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    (Original post by Phalange)
    1) Chemoreceptors are found in medulla, aorta and cartoid artery. Say the chemoreceptor in aorta detected high CO2, low O2 and low pH. It would send impulse via sensory neurone to medulla to decide what to do. What would happen if the medulla detected the high CO2 etc? Would it "skip" the sensory neurone part or...?

    2) IAA inhibits growth in roots but stimulates growth in tips right? Wouldn't gravity cause IAA to accumulate at the tip of the root causing it to stop growing downwards? Unless the root growing region is NOT the tip? :|

    Thanks if anyone can help! Quote me
    Gravity has little effect on IAA, the only thing you need to know is that the IAA is produced in the tip of the plant and is then spread to all sides of the plant. After this the light shining on one side causes the IAA to move to the shaded side of the plant and accumulate there. IAA causes elongation of plant cells so the shaded side of the plant grows faster and the plant bends towards the light so photosynthesis is at its max. There is very little if any mention of IAA affecting the growth in roots in this specification
    The only chemoreceptors to worry about are the ones in the aorta and carotid arteries, they send the impulses to the medulla oblangata which sends impulses via the para- or sympathetic nervous system to the SAN. No point going overboard and revising outside of the course, we'll be given enough information in the actual tests if it goes outside the syllabus.
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    disadvantages and advanategs of using stem cells to treat genetic disorders?
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    (Original post by choc1234)
    hey best of luck
    nd make sure u get some sleep
    Thanks, you too
    Sleep? never lol. I usually go into nocternal mode during exam periods.
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    (Original post by atofu)
    Does anyone have any predictions?
    So far i'm guessing
    - Muscle contractions
    - synapse question (could be with panician cells or cone/rod cells)
    - gene therapy + ethics type question
    - Negative feedback - thermoregulation

    as for the essays i think one could be to do with genetics (possible variation or something)
    I would love a variation essay but unfortunately it was one of the options for last year paper so if genetics probabily about the techniques or ethics
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    (Original post by Jin3011)
    Not sure, I'll just try to get a logical sequence in my head and then start writing about relevant things to the question. Under pressure, I'm really bad at essayst'is the reason I left psychology behind at AS.
    But it's not marked as harshly and structure of the essay plays less of a role but its still a piece of work!
 
 
 
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