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A2 Biology | Post your doubts here

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hassam

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angelgirl:) said:
here they just want to know the rate of photosynthesis ...higher rate means more volume of O2 and the leaf will rise up faster as it experiences upthrust force due to more volume of O2...so they showed the method how to take leaf discs from both types of leaves...they took a syringe, removed the plunger, placed the finger over the open end of the syringe, pored the NaHCO3 solution and then 6 leaf dics in the solution,...now they put the plunger back, put the syringe upside down , means the needle part up...then pushed the plunger upword till all the air comes out, den placed the finger on top of the needle part and pulled the plunger to creat a vaccum, tapped the side of the syringe to remove all the air bubble,till the leaf discs sunk to the bottom- means therez no gas around the disc..as soosn as the disc sink start the timing till it rises up...this time gives us the rate of O2 production during photo..the higher the rate the faster it will rise up and the lesser time it will take...
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well wen we ll be forcing out air...hw i mean.....will not the soln go out....i am nt getting it
 
angelgirl:)

angelgirl:)

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hassam said:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s10_qp_52.pdf
q1 now why we want dry leaves here b4 measuring transpiration rate
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becouse u have to measure the rate of movement of water in the capillary...indirectly the rate of transpiration in the same light intensity throughout the experiment...so if already both type of leavs have some vriable amount of water , will u be able to measure the rate of tranpiration correctly..that the movent of water in the capillary...?
 
angelgirl:)

angelgirl:)

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hassam said:
well wen we ll be forcing out air...hw i mean.....will not the soln go out....i am nt getting it
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no u r not applying large force, u r pushing the piston slowly to make sure just the air should come out not the solution...ok even if little solution comes out it doesnt matter unless u r goin to use the same volume for the next exp.
 
angelgirl:)

angelgirl:)

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hassam said:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s10_qp_52.pdf
question 2 angelgirl:) wh ms does not mentions that volume of 5 cell samples taken from each culture shud also be constant............dont u thnk dats a good enuf control variable.....i dont knw why examiners thinkinng is quite different from myn
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they said that all the volumes/conc. should be constant...means even the volume of the 10 samples out of which 5 u r taking to count the cell no.
but even u r absolutly correct...if u write that u will get mark for sure :)
every1 has differnt way of writing to express their answer unless the concept is correct...
 
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Shafaq Suleman

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dependant var is the concentration of the dye.
although they havent marked it in the ms but i guess i wud be that.n we can measure by the colorimeter
 
princesskt

princesskt

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Shafaq Suleman said:
dependant var is the concentration of the dye.
although they havent marked it in the ms but i guess i wud be that.n we can measure by the colorimeter
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no that is not dependant.....we can not use colorimetre here as we can not seperate the cells.......
 
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