A Level Biology past paper questions for paper 5 (2)

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rate ;: ,
sphere and th e light int ensity often li mi t th e
2 The concentr~tion of carbon dioxide in th e atrno -
photosynthesis.

r in relation to photosynthesis .
(a) Explain what is meant by a limiting facto
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tion s u 1
da , USA. into the ettect of different concentra
(b) Inve stiga tions were carri ed out in Flori osyn thesi s of soyb oc1 ·
ide and of light intensity on the rate of phot
atmo sphe ric carb on diox
plants.
different
com pute r-con trolle d growth chqm bers at
Plants were grow n from seed in outd 9or, pare nt so that
r parts of the cham bers were trans
conc entra tions of carb on dioxide. The uppe
the plan ts rece ived natu ral sunlight.
leav es
soil was sepa rated from the air around the
Afte r the seed lings eme rged , the air in the
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by a gas- tight seal in each cham ber .
rated .
around the leaves of the plants were sepa
Sug gest why the air in the soil and the air

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at differ en!
(c) In one investigation , two sets of
plants , A and B, were grown from seed
concentrations of carbon dioxide :
dioxide (0.033%)
• A - norm al atmo sphe ric concentration of carbon
on dioxide x 2 (0 .066 %).
• B - norm al atmo sphe ric concentration of carb
id e
its particu lar concentration of. carbon diox
Then , keeping each set of plants in 1
es .
photosynthesis at ditferent light 1ntens1t
me asurements were mad e of their rates of

5.
The results are shown in Fig . 2.1 on page

, 2.




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