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AQA BIOL2 Biology Unit 2 Exam - 26th May 2011

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Original post by kingsmod1
nice answer but Nuss was meant to answer that LOL


LOL, oh well sorry, it helped me revise because I had to explain it from memory
Reply 301
Original post by therapist_1
The first division will form two intermediate haploid cells in which both of them will contain 23 chromosomes, with each chromosome having 2 chromatids and so a total of 46 chromatids in each of these 2 cells.

Now the second division occurs, in this the 23 chromosomes with 2 chromatids split to form 2 separate chromatids. These chromatids are now referred to as chromosomes hence forming 4 cells each containing 23 chromosomes.

Main Point: When Chromatids split from the chromosome they become 2 separate chromosomes.

I hope you understand now.:smile:


Thanks so much, that really helps! I understand it now.

And to everyone who says it won't come up, it probably won't, I was just interested in the subject I'm studying and want to understand it fully!
Reply 302
Original post by kingsmod1
how does water enter xylem and how does actice transport of salt help ????

Explain and describe lol


salts reduces wp in root creating wp gradient so water enters by osmosis
apoplast/symplast used to transport water through cortex to xylem

but my real point was, is the stuff on page 134 of the nelson even in the spec?
So has everyone revised cerebral functions???
Reply 304
Original post by James A
lower affinity for oxygen means that when it unloads it, it unloads it easier. am i correct ??


I believe lower affinity for oxygen means when it is shifted to the right.
Original post by TlanTlan
I believe lower affinity for oxygen means when it is shifted to the right.


correct because a high affinity means it binds to it more easily ( moves left ), so yes, your right :biggrin:
Original post by therapist_1
:ff2:
In metaphase chromosomes do not line up at the centromere of the cell they line up at the equator of the cell. Then the centromere of the chromosome is attached to a spindle fibre.

In anaphase the spindle fibres contract and not shorten, you could have lost marks for incorrect terminology.

Its just that, that made me think alot, you were quite right after all.:rolleyes:


no, it is correct in aqa mark schemes to refer to the spindles as shortening.
Original post by affleming
no, it is correct in aqa mark schemes to refer to the spindles as shortening.


Oh I'm sorry,:frown: I answered that just refering to my notes and the text book. Just to stay on the safe side its better to say contracts :iiam:
Reply 308
Or both :awesome:
Original post by al_habib
not fully prepared on these topics :- variation, antibiotic resistance and biodiversity.i have read and understand but i feel am not confident to answer HSW que. do you have any exam questions related to this topics to help me out...:smile:


Yehh av ucheked out the bio unit 2011 paper
its on biodiversity its goes on the lines of:
what effect does agriculture have on biodiversity of animals
then u talk about the three factors: genetid diversity reduce obviosly
but alwais talk about
the use of pesticides
fewer food sources
fewer habitats

yh so remember that
so far interspecif ad intraspecific variation hasnt kum up so make sure u knw that
jus mak esure u knw unit2 jan 11 paper! let me knw if u need any help on it
Could someone explain answer of question 5dii in the June 2010 paper please?

Also what does the term degenerate mean for DNA base sequences?
Original post by Insanity514
Could someone explain answer of question 5dii in the June 2010 paper please?

Also what does the term degenerate mean for DNA base sequences?


degenerate means that more that one codon (triplet of bases that codes for a single amino acid) codes for the same amino acid.

So, say the amino acid is Methionine, the code is degenerate because AAG & ATT & ACT each code for methionine. (fictional btw, but the principle is the same)
Original post by ChessMister
degenerate means that more that one codon (triplet of bases that codes for a single amino acid) codes for the same amino acid.

So, say the amino acid is Methionine, the code is degenerate because AAG & ATT & ACT each code for methionine. (fictional btw, but the principle is the same)


Thanks mate :wink:
Reply 313
Original post by Insanity514
Could someone explain answer of question 5dii in the June 2010 paper please?

Also what does the term degenerate mean for DNA base sequences?


Well i just read the exam report on 5dii , and it seemed that less than 10% of candidates actually got that mark, indicating that in true aqa style it was a stupid question.
Reply 314
Original post by aleema1992
Yehh av ucheked out the bio unit 2011 paper
its on biodiversity its goes on the lines of:
what effect does agriculture have on biodiversity of animals
then u talk about the three factors: genetid diversity reduce obviosly
but alwais talk about
the use of pesticides
fewer food sources
fewer habitats

yh so remember that
so far interspecif ad intraspecific variation hasnt kum up so make sure u knw that
jus mak esure u knw unit2 jan 11 paper! let me knw if u need any help on it


thanx for that, i'll do the paper tomorrow and i'll let you knw any problems that will crop up.have you finished ol bio Past papers..:smile:
Reply 315
Original post by TlanTlan
Well i just read the exam report on 5dii , and it seemed that less than 10% of candidates actually got that mark, indicating that in true aqa style it was a stupid question.


You just have to do 2 to the power 3. 2 being a constant number and 3 being the number of chromosomes. Look at page 141 on the nelson thornes book at the hint box :smile:
Reply 316
Original post by Insanity514
Could someone explain answer of question 5dii in the June 2010 paper please?

Also what does the term degenerate mean for DNA base sequences?


You just have to do 2 to the power 3. 2 being a constant number and 3 being the number of chromosomes. Look at page 141 on the nelson thornes book at the hint box. :smile:
Reply 317
Can someone please explain how water is transferred up from the xylem? I believe there are two ways. Can you also make your answer specific to what the markscheme answer for such a question would be.

:smile:
Original post by Insanity514
Could someone explain answer of question 5dii in the June 2010 paper please?

Also what does the term degenerate mean for DNA base sequences?


thats 8 luz it 2*2*2=8 its 2 to the power of 3
denegernate is when when more than 3 dna base sequences (more than 1 trriplet coded)
Where can i find the examiner reports, please upload or post a link.

Thanks,

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