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Scienceisgood
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(Original post by starfish232)
Hi could someone please explain why in the june 2010 paper the answer to question 5d(ii) is 8. I don't understand how they got the answer. Also, could someone please how the apparatus used in question 4 works? I don't understand how the potometer allows you to measure rate of water uptake.

Thanks

http://filestore.aqa.org.uk/subjects...W-QP-JUN10.PDF

http://filestore.aqa.org.uk/subjects...W-MS-JUN10.PDF
I asked the exact same question as you ages ago. =P
Here is a link to the explanation of that question:

http://www.thestudentroom.co.uk/show...2#post42113722
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Melissajwilson
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How do you calculate percentage change? And does anyone have any set answers for how science works questions


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Scienceisgood
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(Original post by Melissajwilson)
How do you calculate percentage change? And does anyone have any set answers for how science works questions


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Difference over initial.

Example - There were 25 rabbits in a field and 2 hours later, there were 19, calculate the percentage change.

(25-19)/25 * 100 = 24% decrease.
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starfish232
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(Original post by Scienceisgood)
I asked the exact same question as you ages ago. =P
Here is a link to the explanation of that question:

http://www.thestudentroom.co.uk/show...2#post42113722
Thanks
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Melissajwilson
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(Original post by Scienceisgood)
Difference over initial.

Example - There were 25 rabbits in a field and 2 hours later, there were 19, calculate the percentage change.

(25-19)/25 * 100 = 24% decrease.
Cheers


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chrishy2012
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#586
anyone has the january 2013 paper and marks scheme? Thankyou!!!!!!!!!!!!!!!!!!!!!!!
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dooobie_
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Going to fail
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Paulineuh
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(Original post by chrishy2012)
anyone has the january 2013 paper and marks scheme? Thankyou!!!!!!!!!!!!!!!!!!!!!!!
http://www.thestudentroom.co.uk/show...&page=3&page=3
Mark scheme! Can't find the question paper though :confused:
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Melissajwilson
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Does water move via the symplastic pathway by diffusion or osmosis?


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Paulineuh
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(Original post by Melissajwilson)
Does water move via the symplastic pathway by diffusion or osmosis?


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If we are talking about plants here, water moves via osmosis by either the symplastic pathway or apoplastic pathway
Water always moves by osmosis.
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Scienceisgood
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(Original post by chrishy2012)
anyone has the january 2013 paper and marks scheme? Thankyou!!!!!!!!!!!!!!!!!!!!!!!
https://skydrive.live.com/?cid=ab9a5...012167BC%21110

Link to my skydrive. =)
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JackTheNerd
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#592
Does someone have the Jan 2013 paper for Biol2

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Manni
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Can someone summaries the differences between symplastic pathway and apoplastic pathway
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Melissajwilson
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(Original post by Paulineuh)
If we are talking about plants here, water moves via osmosis by either the symplastic pathway or apoplastic pathway
Water always moves by osmosis.
But osmosis is the movement of water from a high concentration to low concentration through a partially permeable membrane?


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homefind
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(Original post by Melissajwilson)
But osmosis is the movement of water from a high concentration to low concentration through a partially permeable membrane?


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It's technically diffusion in the apoplastic pathway


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Swords N Thorns
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In standard deviation, 'overlap' means that the results are more likely to be due to chance, right?

I really don't understand how you can tell if it's 'overlapping' just by looking at the numbers, and I really don't understand why overlapping means the results are more likely to be due to chance.

Sorry for the bad wording, hoping someone might be able to help me out here.
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starfish232
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(Original post by Swords N Thorns)
In standard deviation, 'overlap' means that the results are more likely to be due to chance, right?

I really don't understand how you can tell if it's 'overlapping' just by looking at the numbers, and I really don't understand why overlapping means the results are more likely to be due to chance.

Sorry for the bad wording, hoping someone might be able to help me out here.
With the numbers, generally they show the +/- SDs alongside the values. You generally see if they over lap or not if the values are different to each other but if you find it difficult then you can just add and subtract the SDs from the value giving you a range for reach value. Looking at the ranges you can tell if there's any overlap or not.

Standard deviation shows spread of data about the mean. If there's overlap in standard deviation then that means that any difference in the results is more likely due to chance. In order for any difference in results not being due to chance then you would expect there to be no overlap,

Does this make sense? Not the best explanation...
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starfish232
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Could someone please clarify that reason of one of the answers being 'less carcinogens' for 10e(iii) jan 2012 paper is because the reduced blood flow means lesser amount of carcinogens being received in those certain parts of the brain?
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Paulineuh
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(Original post by Melissajwilson)
But osmosis is the movement of water from a high concentration to low concentration through a partially permeable membrane?


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Ah, then I believe its diffusion... I always thought any movement of water was osmosis. :confused:

EDIT: In my Nelson Thornes textbook, it says "osmosis" and the differences in water potential that make the water move through the symplastic & apoplastic pathways.


(Original post by starfish232)
With the numbers, generally they show the +/- SDs alongside the values. You generally see if they over lap or not if the values are different to each other but if you find it difficult then you can just add and subtract the SDs from the value giving you a range for reach value. Looking at the ranges you can tell if there's any overlap or not.

Standard deviation shows spread of data about the mean. If there's overlap in standard deviation then that means that any difference in the results is more likely due to chance. In order for any difference in results not being due to chance then you would expect there to be no overlap,

Does this make sense? Not the best explanation...
I was confused with SD but now it makes more sense! Thank you :yep:

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Swords N Thorns
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(Original post by starfish232)
With the numbers, generally they show the +/- SDs alongside the values. You generally see if they over lap or not if the values are different to each other but if you find it difficult then you can just add and subtract the SDs from the value giving you a range for reach value. Looking at the ranges you can tell if there's any overlap or not.

Standard deviation shows spread of data about the mean. If there's overlap in standard deviation then that means that any difference in the results is more likely due to chance. In order for any difference in results not being due to chance then you would expect there to be no overlap,

Does this make sense? Not the best explanation...
Yes! Thank you!
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