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OCR 2010 A2 Biology Unit 2 - Control, Genome and Environment watch

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    [QUOTE=ViolinGirl]
    (Original post by ACDC)
    can you explain the highlighted in laymans terms, causes thats confused me even more, lol.

    also, dont you mean apical where you put lateral in brackets?

    the reason why im confused with apical dominance is because of this paragraph in the ocr revision guide:

    in many plants, side shoots do not grow if the main shoot is growing. however, if the bud at the tip of the main shoot (apical/termind bud) is removed, the the lateral buds will start growing. this effect may be caused by auxins produced by the apical bud inhibiting groth of lateral buds. removing the apical bud removes the source of the inhibiory auxin.

    QUOTE]

    The paragraph makes perfect sense.
    The shoot grows, means auxins are being produced in the apex, so the presence of auxins inhibits the growth of side stems.
    Shoot is cut, auxins are no longer produced at tip = no longer inhibit growth of stem= stems can grow!

    I shall try and explain the rest simply:

    Apical dominance is when the growth of the apical bud at tip of stem, inhibits the growth of lateral stems further down the shoot.

    This is because auxins are produced in shoot tip. Auxins are hormones that inhibit growth of lateral shoots. When the tip is cut off, the auxins are no longer produced, so there is nothing preventing the growth of the stems further down the shoot.

    There is really nothing more to it. You just need to know the evidence that can be used to prove this is the case-that auxins are the inhibitors and there are various bits of info that show this, but also that there are 2 other hormones involved- abscinsic acid and cytokinins.
    so if you want a tree thats shaped like a conifer you have to cut the apical bud? is there a way for this shape to take form w/o having to cut the tip?

    and how come you dont get like a rectangular shape when the tip is removed as the auxin is made in the tip, i know that sounds silly, but if no tip = no auxin. why dont the middle and top of the tree show the same level of lateral growth as the bottom of the tree?
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    student92 you are my life right now

    regarding plants: my mum is growing some tomato plants and was confused why when she snapped off the tip of one it started to shoot out from the sides so i pomptly explained to her, helping me to revise too

    good times!
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    (Original post by dopeyangel101)
    student92 you are my life right now

    regarding plants: my mum is growing some tomato plants and was confused why when she snapped off the tip of one it started to shoot out from the sides so i pomptly explained to her, helping me to revise too

    good times!
    Hehe I do stuff like that all the time...the response: eyes, roll 'Damn she's started again'
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    Right ive covered the syllabus of this unit now. I have to revise for the resit (F214) and how on earth is anyone going about revising the other synoptic stuff? learning it all or just looking through it to refresh your memory?
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    (Original post by Falcon91)
    Right ive covered the syllabus of this unit now. I have to revise for the resit (F214) and how on earth is anyone going about revising the other synoptic stuff? learning it all or just looking through it to refresh your memory?
    Past paper + Re-reading the whole book.
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    here is a summary when a action potential arrives at muscle cell

    sarcolemma depolarises. depolarisation spreads down the transverse tubules to the sarcoplasmic reticulum. sarcoplasmic reticulum release Ca ions into sarcoplasm. Ca ions bind to troponin which causes it to change shape. this pulls the the tropomyosin away from the actin - myosin binding site on actin filament. this exposes the binding site. myosin heads can attach to actin - myosin binding sites, therefore a cross bridge forms.

    power stroke......
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    what are the commercial uses of cytokinins -

    i always remember the uses of gibberallins and auxin not cytokinins.
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    (Original post by TX22)
    what are the commercial uses of cytokinins -

    i always remember the uses of gibberallins and auxin not cytokinins.
    The uses of cytokinins is that its used to delay leaf senescence as well as stimulating apical bud growth (so used for micropropagation of plants by tissue culture).
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    (Original post by ibysaiyan)
    Past paper + Re-reading the whole book.
    Past papers for our full units dont exist. Err...central concepts is more similar to F214, not really the same as doing a proper past paper.

    I guess ill just re-read and relearn, had a rubbish/failed hour of revision just now didnt get anything done.

    So will do an hour or two from 6 onward
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    (Original post by TX22)
    what are the commercial uses of cytokinins -

    i always remember the uses of gibberallins and auxin not cytokinins.
    Cytokinins

    Benzyladenine
    - Improves fruit quality
    - Prolongs life storage of green vegetables

    Kinetin
    - Used in tissue culture
    - Stimulates cell division of lateral bud to give shoot growth.
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    (Original post by student92)
    Cytokinins

    Benzyladenine
    - Improves fruit quality
    - Prolongs life storage of green vegetables

    Kinetin
    - Used in tissue culture
    - Stimulates cell division of lateral bud to give shoot growth.
    Keep those notes coming, they're brilliant.
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    Measuring energy transfer

    - Energy originally comes from the sun light.
    - Plants capture light energy through photosynthesis and convert it into chemical energy which is stored.
    - Food chain - shows the transfer of energy from one living organism to another. Grass >> Rabbit >> Fox
    - Food web - shows the transfer of energy through the whole ecosystem.
    - Arrows - shows the direction of energy transfer
    - Energy cannot be recycled.


    The efficiency of energy transfer

    - Some of the energy is lost at each trophic level which is unavailable to organisms at the next trophic level.
    - Some of the energy is lost to:
    - Respiration
    - Heat loss
    - Faeces, Urine (which is only available to decomposers)

    - Less energy available to sustain living tissue at a higher level of the food chain > less living tissue kept alive > fewer consumers at higher level of the food chain > can be shown by a pyramid of number (if the same size)
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    (Original post by Liverpool F.C.™)
    Keep those notes coming, they're brilliant.
    Yes sir!
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    (Original post by Liverpool F.C.™)
    Keep those notes coming, they're brilliant.
    agreed so useful!
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    Good good =}
    keep it up!
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    The apical bud (or tip) produces the growth hormone auxin, which not only promotes cell division, but also diffuses downwards and inhibits the development of lateral bud growth which would otherwise compete with the apical tip for light and nutrients. Removing the apical tip and its suppressive hormone allows the lower dormant lateral buds to develop and the buds between the leaf stalk and stem to produce new shoots which compete to become the lead growth. Manipulating this natural response to damage (known as the principle of apical dominance) by processes such as pruning (as well as coppicing and pollarding) allows the horticulturist to determine the shape, size and productivity of many fruiting trees and bushes.
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    Hope that helps guys
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    does anyone feel there is so much content.
    my head is about to explode with all this revision.


    what does everyone predict will come up?
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    (Original post by MadMaths)


    Hope that helps guys
    :eek: Where the hell do you get these from ?

    Thanks keep them coming.
 
 
 
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