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A2 Biology OCR June 2015 Revision Thread

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Can someone please 'outline the need of a communication system'' (4)
Original post by catrionaw
Can someone please 'outline the need of a communication system'' (4)


Organisms need to respond to external stimuli, e.g. temperature, oxygen concentration and levels ofsunlight. These may be over time, e.g. winter fur to summer fur, or quickly, e.g. dilation and constriction of pupils.Internal environments changes too - the build up of carbon dioxide as a result of respiration changes the pHof the tissue fluid, and therefore inhibits enzyme activity. Multicellular organisms need to coordinatedifferent organs, so this requires a good communication system which will:
• Cover the whole body
• Enable cells to communicate with each other
• Enable specific communication
• Enable rapid communication
• Enable both short and long-term responses.
http://us20.chatzy.com/13203795560052 Guys join us on this chat if you want to revise and help each other :smile:
Original post by YouAgain
Organisms need to respond to external stimuli, e.g. temperature, oxygen concentration and levels ofsunlight. These may be over time, e.g. winter fur to summer fur, or quickly, e.g. dilation and constriction of pupils.Internal environments changes too - the build up of carbon dioxide as a result of respiration changes the pHof the tissue fluid, and therefore inhibits enzyme activity. Multicellular organisms need to coordinatedifferent organs, so this requires a good communication system which will:
• Cover the whole body
• Enable cells to communicate with each other
• Enable specific communication
• Enable rapid communication
• Enable both short and long-term responses.



Thank You! :h:
Original post by Beni24
Has anyone done January 2013 paper for F214? Can someone please explain how they got percentage answer? i dont understand :?


10807.1-11671.4=-864.3 so this is the total reduction in Mean yield for the crop

Divide by the yield without treatment and multiply by 100

=-7.4% decrease.
(edited 8 years ago)
Original post by Beni24
Has anyone done January 2013 paper for F214? Can someone please explain how they got percentage answer? i dont understand :?


First calculate the difference between mean yield not treated with herbicide, and the mean yield treated with herbicide which is -864.3.

Then divide this by the original value which is 11671.4 (from the table) and the answer is -0.0740. x 100 which is -7.4. I think? :smile:
Please count someone summarise light harvesting/antanne complex stuff? Its not in the textbook but there was an exam question on it recently ahhh help!
Hey has somebody created a practice paper for f214/f215 based on predictions? Someone did it this year for AS exams.. might have been @kingaaran ? Unsure but it was really helpful
Original post by Zeshaan
Hey has somebody created a practice paper for f214/f215 based on predictions? Someone did it this year for AS exams.. might have been @kingaaran ? Unsure but it was really helpful


Hey there :smile: I did already say this but it's gotten a little buried in the thread! My teacher who is an examiner and helps to write the F215 exam said we have reached the end of a seven year paper cycle. Last years paper was full of the things that they didn't get to fit into the previous six years. Therefore our paper this year could contain anything, irrespective of what has come up in 2013 etc.

Having said that I'm sure the same stuff as last year won't come up, they'll probably still try to make the paper different from last year :smile: Hope that helps :smile: (although unfortunately it doesn't help with the predictions!)
Original post by maisie__x
Hey there :smile: I did already say this but it's gotten a little buried in the thread! My teacher who is an examiner and helps to write the F215 exam said we have reached the end of a seven year paper cycle. Last years paper was full of the things that they didn't get to fit into the previous six years. Therefore our paper this year could contain anything, irrespective of what has come up in 2013 etc.

Having said that I'm sure the same stuff as last year won't come up, they'll probably still try to make the paper different from last year :smile: Hope that helps :smile: (although unfortunately it doesn't help with the predictions!)


Oh wow, thank you for telling me I appreciate it! Ah so no topics are more likely to come up :frown: gonna have to be prepared for literally everything then..
Original post by Zeshaan
Oh wow, thank you for telling me I appreciate it! Ah so no topics are more likely to come up :frown: gonna have to be prepared for literally everything then..


That's okay! :smile: It's annoying though isn't it! I still think last years stuff is unlikely to come up again though :smile:
Hey @maisie__x is that the same for f214 too?
does cyclic and non cyclic phosphorylation occur at the same time? :smile:
Original post by Zeshaan
Hey @maisie__x is that the same for f214 too?


Yes, unfortunately!
I am really dreading f214 exam on Monday :/


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Original post by Beni24
does cyclic and non cyclic phosphorylation occur at the same time? <img src="images/smilies/smile.png" border="0" alt="" title=":smile:" smilieid="1" class="inlineimg" />


No, cyclic happens in the absense of co2 as Calvin cycle cannot occur and non cyclicnhappens when there is light and there is co2available.

Also, NEVER say phosphorylation, it's Photophosphorylation
Original post by Beni24


I recommend mrbiotom1, he's really good and covers the whole course as he did the videos during his a level
Original post by ChoccyPhilly
No, cyclic happens in the absense of co2 as Calvin cycle cannot occur and non cyclicnhappens when there is light and there is co2available.

Also, NEVER say phosphorylation, it's Photophosphorylation


Thank you! so what happens to the ATP thats made in cyclic photophosphorylation?
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Klesia
Original post by Beni24
Thank you! so what happens to the ATP thats made in cyclic photophosphorylation?


The ATP that is made in cyclic photophosphorylation is used in the calvin cycle to reduce and phosphorylate GP so it becomes Triose phosphate, in which carbohydrates and lipids are formed

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