Qualification > Sciences
Biology Paper 1
sisler:
--- Quote from: kam on June 05, 2009, 08:04:01 am ---
--- Quote from: sisler on June 05, 2009, 08:01:01 am ---hey ...
can anyone help me wid may/june2003 paper 1 - question 30 i dont understand how the answer is D
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pollen grains are plants sex cells
so they have half
the answer is B
even in mark scheme
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thx probably the markshceme i have is wrong
Kim:
--- Quote from: Feva on June 05, 2009, 08:32:38 am ---can someone explain transpiration ?
and the functoin on phloem?
Thank You
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transpiration is when the plant loses water throgh the leaves in the form of water vapour
it is reduced due to presence of the waxy cuticle but can not be stopped
their are 5 factors affecting transpiration
1-humidity
2-temperature
3-stomata
4-light intensity
5-surafce area
phloem is made of livivg cells arranged end to end with cross walls wid pores
it has nucleus and cytoplasm
its main function is the transport of sugars in the form of sucrose from ares of manufacture to areas of utilization
hope this helps
Feva:
Thanks man ;D
+rep
kam:
so if there was high humidity high temps etc
the rate of transpiration increases?
camel:
--- Quote from: 247sports on June 05, 2009, 08:05:46 am ---k nitrogen cycle very easy
first:
there is 79% of nitrogen in air which is inert i.e. doesnt react....but then some oragnisms need nitrogen to live so hw do they use it ??
this is done by the decomposers..turning nitrogen in a very usefull or in reactive form is calld nitrogrn fixation..
first lightin causes the nitrogen to react with oxygen to form its oxides..then they idssolve in rain and are washed into the soil where the decomposers convert it into nitarates or NH3....nw nitrogen-fixin bacteria they use nitorgen gas form the air n combine it with other sustances to make nitrtes n other usefull compounds...there is another bacteria who does teh opposite it converts the nitrates into nitrogen gas....its calld denitifyin bacteria...
n also these bacteria they breakdown the waate of naimal into nitarates too
phew anewho hope this helps n i think this is enuf for nitrogrn cycle
WHISH ME LUCK MY XAM IN 1 HR :s
thank you, that helped :P
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