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AQA BIOL2 Biology Unit 2 Exam - 26th May 2011 watch

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    Arghhh, this is bad i'm still getting confused is transpiration..

    A- evaporation of water vapour from plants
    or
    B- Uptake of water through a plant or tree

    ??
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    Just got 71/85 on June 2010 mock... think I marked it fairly

    Now im gonna do Core2 Math papers for my exam in morning tomorrow instead

    Happy with that lol, good luck everyone x
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    (Original post by iguess)
    Arghhh, this is bad i'm still getting confused is transpiration..

    A- evaporation of water vapour from plants
    or
    B- Uptake of water through a plant or tree

    ??
    Transpiration is the evaporation of water from leaves
    The Transpiration Stream is the passage of water through a plant. :-)
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    (Original post by iguess)
    Arghhh, this is bad i'm still getting confused is transpiration..

    A- evaporation of water vapour from plants
    or
    B- Uptake of water through a plant or tree

    ??
    A. B is transpiration pull.
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    (Original post by ??????????????????)
    Probably not as a 6 marker then.
    If it does, just mention counter currant system creates a concentration gradient allowing easier diffusion of oxygen into the blood. Stacked filaments and stacked lammele to increase surface area which also increases rate of respiration. Say it needs this because less oxygen in water than air.
    Yep, and DNA hybridisation has come up in June 2010 so not that either. Probably:
    tissue fluid
    gas exchanges in plants
    Meiosis/Mitosis

    Has factors affecting transpiration come up, I have feeling I've come across it?
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    (Original post by iguess)
    Arghhh, this is bad i'm still getting confused is transpiration..

    A- evaporation of water vapour from plants
    or
    B- Uptake of water through a plant or tree

    ??
    Evaporation of water causes transpiration as water leaves the leaves causing a lower water potential so water travels from the soil, into root hair cells through the cortex, either atoplastically or systoplastically. Root pressure, cohesive tension and something else I forgot push it up.
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    (Original post by ??????????????????)
    The water molecules have hydrogen bonds between each molecule so this causes them to stick to each other creating tension. You also have adhesive which causes it to stick to the walls of the stem. Cohesive is useful because it causes water to easily go up the stem when as it is pulled up by the others. Adhesive prevents the water falling back down the stem due to gravity.

    So when water evaporates from the spongy mesophyll, the water potential is lowered. Mineral ions are pumped into the xylem through active transport to lower the water potential as well. Water goes up the stem. The cohesive forces cause it to pull up other water molecules and adhesive prevent it falling. Might also mention root pressure.
    I think thats cohesion which causes water molecules to stick together, and tension which pulls more water in to the leaf
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    (Original post by Some random guy)
    A. B is transpiration pull.
    Thanks! It's because the NT book has the first definition!!
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    (Original post by iguess)
    Arghhh, this is bad i'm still getting confused is transpiration..

    A- evaporation of water vapour from plants
    or
    B- Uptake of water through a plant or tree

    ??
    Transpiration is the upward moving column of water in a plant from the roots cells to the stomata, according to my textbook. Its what happens after B, in your post, and A happens after transpiration. The evaporation of water from plants helps to maintain transpiration rate, as it creates a water potential gradient in the stomata.

    (Original post by Jorgeyy)
    Just got 71/85 on June 2010 mock... think I marked it fairly

    Now im gonna do Core2 Math papers for my exam in morning tomorrow instead

    Happy with that lol, good luck everyone x
    AQA have a UMS converter, so 71/85 converts to 136/140, which is almost full marks, as you can see. 73 marks is 140/140, so good work. If you want to check your other papers-http://web.aqa.org.uk/UMS/ums_converter_as.php?id=04
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    http://www.studentcreche.co.uk/resources/biol5.pdf

    please pass this on to other people so it helps everyone! i just hope i told you this much earlier!
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    (Original post by BeejTheone)
    I think thats cohesion which causes water molecules to stick together, and tension which pulls more water in to the leaf
    I said that. Maybe poorly worded. The water is bonded with hydrogen bonds that cause them to stick to each other so when one is pulled they are also pulled with it. However tension is also created cos it's a bond. If you have a tug of war, there is tension due to the pulling.
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    (Original post by ??????????????????)
    I said that. Maybe poorly worded. The water is bonded with hydrogen bonds that cause them to stick to each other so when one is pulled they are also pulled with it. However tension is also created cos it's a bond. If you have a tug of war, there is tension due to the pulling.
    Oh right i thought you mixed cohesion and tension up. Anyway gl tmo
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    (Original post by iguess)
    Yep, and DNA hybridisation has come up in June 2010 so not that either. Probably:
    tissue fluid
    gas exchanges in plants
    Meiosis/Mitosis

    Has factors affecting transpiration come up, I have feeling I've come across it?
    I saw a 1 mark question on it asking for one factor in June 2010, and i swear i saw it a fair amount in Jan 2011, but not as a 6 mark question, so it could be.
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    (Original post by cobra2k10)
    http://www.studentcreche.co.uk/resources/biol5.pdf

    please pass this on to other people so it helps everyone! i just hope i told you this much earlier!
    this is superb stuff, very handy lol

    oh yeah btw you display pic of the cobra is funny, dunno why
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    (Original post by lolo-x)
    The cohesion part is the attraction between individual water molecules, caused by the hydrogen bonds between them. It causes 'surface tension' and the 'meniscus' on the surface of water and, in the xylem of plants, causes each water molecule in a xylem vessel to be attracted to its neighbours.
    Thus, if a water molecule is lost from the TOP of a plant, it will pull on its neighbour, which will pull on its neighbour, which wil....etc etc, all the way to the BOTTOM of the plant, where water will be attracted into a root hair.

    The tensionpart refers to the water being PULLED UP the plant, as opposed to being PUSHED up the plant. The pressure inside each xylem vessel is thus negative (BUT positive inside the phloem, hence maple syrup and latex coming out when a tree is tapped), in just the same way as the pressure is negative inside a drinking straw when you suck.

    This is the opposite of the situation inside domestic water pipes, where the pressure is poitive and water squirts out when you nail through a pipe!

    So....water is lost from the leaves through evaporation,; it sucks water up the plant and the attraction between water molecules causes the water to be pulled all the way up the plant.

    (Original post by ??????????????????)
    The water molecules have hydrogen bonds between each molecule so this causes them to stick to each other creating tension. You also have adhesive which causes it to stick to the walls of the stem. Cohesive is useful because it causes water to easily go up the stem when as it is pulled up by the others. Adhesive prevents the water falling back down the stem due to gravity.

    So when water evaporates from the spongy mesophyll, the water potential is lowered. Mineral ions are pumped into the xylem through active transport to lower the water potential as well. Water goes up the stem. The cohesive forces cause it to pull up other water molecules and adhesive prevent it falling. Might also mention root pressure.

    thank you so much guys, this is very helpful
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    (Original post by Twigleheight)
    The gamete will have 3 chromosomes in it so you do 2 to the power of 3
    So basically 2x2x2 which is 8.

    For example, if the gamete had 6 chromosomes in you would do 2x2x2x2x2x2
    but the gamete in that question does have 6 chromosomes
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    Absolutely bricking it now...
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    (Original post by Jim Lee)
    Transpiration is the upward moving column of water in a plant from the roots cells to the stomata, according to my textbook. Its what happens after B, in your post, and A happens after transpiration. The evaporation of water from plants helps to maintain transpiration rate, as it creates a water potential gradient in the stomata.
    That's much better, by the way sorry what book do you have if you don't mind me asking because I want to start learning A2 early?

    (Original post by Jim Lee)
    I saw a 1 mark question on it asking for one factor in June 2010, and i swear i saw it a fair amount in Jan 2011, but not as a 6 mark question, so it could be.
    No wonder, that's the paper I done as a mock. Let's just hope AQA don't pull any new tricks out the bag!
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    In the formation of tissue fluid how is hydrostatic pressure created?
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    (Original post by Jim Lee)
    Transpiration is the upward moving column of water in a plant from the roots cells to the stomata, according to my textbook. Its what happens after B, in your post, and A happens after transpiration. The evaporation of water from plants helps to maintain transpiration rate, as it creates a water potential gradient in the stomata.



    AQA have a UMS converter, so 71/85 converts to 136/140, which is almost full marks, as you can see. 73 marks is 140/140, so good work. If you want to check your other papers-http://web.aqa.org.uk/UMS/ums_converter_as.php?id=04
    Bro I got 60/85 on Jan 2011 before I even did any revision in my mock like 2 weeks ago and that's 129 UMS (my teacher marked this so it's deffo legit)

    And now I just got 71...

    How can I not get an A now !!!!! wooooooop
 
 
 
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