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BIOL4 Biology Unit 4 Exam - 13th June 2011

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would people say this was in the middle in terms of difficulty between june 2010 and january 2011's papers? jan was 52 for an A* but june was 39 for an A* ... out of 75 btw.

Reply 1401

khimmy

omg.. hardy weinberg.. how can i be so stupid.. i read the question i remember it saying homozygous recessive YET i calculated for heterozygous!!! arghh and i was feeling confident until i realised my mistake.. damnnn!!

Reply 1402

SK-mar

Original post by peachtoast

But the main point (other than the 2ATP from glycolysis) is to regenerate NAD from NADH so glycolysis can continue, which is why no ATP is produced by the fermentation part.

yeh but the whole reason for anerobic respiration is so that NAD is regenerated in order to produce ATP. although its generated from the glycolysis stage it can only happen because of the regeneration of NAD and its all a part of anaerobic respiration as a whole. just like when oxygen is present, ATP produced in glycolysis is a part of aerobic respiration.

Reply 1403

leo123

Original post by khimmy

my friends say it was homzygous dominant and there i realised my mistake
because i got 0.4475 44.75%

Reply 1404

username554371

Original post by SK-mar

Yeah, to continue the cycle, so anaerobic respiration exists to regenerate for further glycolysis (so the organism can at least get 2ATP from each glucose). I do feel silly for not ticking that one, it seems really obvious now! :facepalm2:

Reply 1405

MessyRoom

Original post by SK-mar

thats a good point. didn't think of that. to be honest i was so rushed in this question, had about 7 mins to do it all. for the why is random data collection necessary what did you put?

I just said the standard 'it removes bias from the experiment' ... i then babbled but said that it would allow us to formulate a valid correlation between mite numbers and successful breeds.

I said the same and then gave an example like "random sampling removes bias eg, a scientist may prefer to sample the lower lying nests for safety reasons" OWTTE

Feeling fairly confident of a B minimum.

Reply 1406

khimmy

Original post by leo123

my friends say it was homzygous dominant and there i realised my mistake
because i got 0.4475 44.75%

Is it?? arhhh i can't even remember anymore and in the exam i thought i understood hardy weinberg.. maybe not lool :s-smilie:

Reply 1407

Jing_jing

Original post by SK-mar

would people say this was in the middle in terms of difficulty between june 2010 and january 2011's papers? jan was 52 for an A* but june was 39 for an A* ... out of 75 btw.

Was June the shrew paper? I expect that the grade boundaries for that were so low because the paper was horrific apparently and there were so many complaints! I think that the paper is around the same difficulty as January. I hope the mark scheme is lenient though, there were so many vague questions that could be interpreted different ways! I did think the end questions were good though :smile:

Reply 1408

Superlogon

Original post by leo123

my friends say it was homzygous dominant and there i realised my mistake
because i got 0.4475 44.75%

homozygouse was actually 64% anywho.
Homodominant=64%
hetero=32%
homorecessive=4%

I worked them all out to completly cover every angle possible! :P

Reply 1409

Superlogon

Original post by khimmy

Is it?? arhhh i can't even remember anymore and in the exam i thought i understood hardy weinberg.. maybe not lool :s-smilie:

If you got 4% you were correct.

Reply 1410

leo123

Original post by khimmy

Is it?? arhhh i can't even remember anymore and in the exam i thought i understood hardy weinberg.. maybe not lool :s-smilie:

even if you worked out heterozygous, you must have worked out recessive alleles and dominent so you might get 1 mark probably :smile:

Reply 1411

superminh21

In the life expectancy question, I assumed that life expectancy was the age that 50% of the population reached. Were I right or will I lose 1 mark ?

Reply 1412

khimmy

Original post by Superlogon

If you got 4% you were correct.

hehe lool yea but thats the thing i didnt i calculated for hetero recessive and got 16% :frown:

Reply 1413

altudios

Particularly Ambiguous Questions:
1) a) ? Ticky table: Seems likely that ETC ticked for both photosynth and aerobic resp, rather unambiguously as it turns out. However, ATP production is ambiguous for photosynth - although overall it produces none, and one wouldn't argue that it produces RuBP overall, for example but rather that overall CO2 + H2O --> O2 + C6H12O6. Personally sway towards no tick for ATP production in photosynth.
2) ? Horse excess energy thing: I think past examination papers suggest that anything reasonable goes for this. I stated that it might be stored as fat, for example. Not in depth, but not sure how much depth was really expected.
3) Reason for different net productivity: I suspect any reasonable reason related to time of year, taking into account change in one value and constance of another, will get marks. I hope.
4) Advantages of anaerobic waste thing: Meh, anything sensible, e.g. use methane instead of waste energy, lack of eutrophication due to to containment of waste etc. Temp question not ambiguous - high temp due to respiration of bacteria, denaturation will occur (think of steaming horse poop - same reason for steam).
5) Cats. Stupid cats: Ambiguous q on possibility of raising all choc cats. I have no idea on this one - misread or didn't read fully, so it made little sense and I missed it out. Because of this all previous suggested answers to this q on TSR seem decent to me.
6) Human populations/life expectancy differences - obvious differences in life expectancy. Reasons numerous and probably all logical answers accepted. For birth rate question, I would expect to be marked wrong if definition is not equivalent to number of births in year/ population in year * 1000 (so I got it wrong, as accidentally wrote * 100, which was Very Special of me).
7) Birds and mites and oil: This was a particularly irritating question for me. It looks like I misread "effect of simultaneous measurement on reliability" q as being exclusively negative, and didn't think it was, so skipped it, when I could have written that it was a good idea, as minimised differences in mite counts due to passage of time. Mite correlation question - looks in retrospect like correlation was barely in existance, but in feverish exam state I thought correlation was clear but required more data. May be hope for both answers. Oil gland correlation description - was a couple of marks, so really good description needed I suspect, which I didn't give - just vague mention of correlation.
8) Long answers: All lovely. See previous mark schemes for near same form of q and level of depth.

Can't remember which q the Hardy-Weinberg/selection question was in, suspect 'twas inheritance? Or was it 2) This is not that ambiguous. We are told that one allele is very rare, and by extension another is common. We are told that very rare allele frequency drops over time. Thus rarest genotypes containing t, rare allele, decrease in frequency. This is removal of extremes. We cannot say it is directional - the average individual does not possess the t allele. People who say that selection is favouring one extreme and not the other, thus directional selection is occurring, are making a strange jump. If choosing one allele over another and changing frequencies of alleles is directional selection, then all selection is directional selection. In the whole world. This is false. Thus; stabilising.

Have I missed out any other doozies?

Reply 1414

SK-mar

Original post by Jing_jing

nah i didn't include the shrew papers questions - that was jan 2010. im referring to jan 2011 and june 2010. But yeh i reckon that it was slightly harder than this jan's paper as it was so so so vague at times! must agree though, last questions were quite beautiful...

although apparently the dead leaves one was only referring only to how nitrogen is made available to plants and didn't want how carbon is made available. i mentioned all the nitrogen stuff, but also mentioned how the decomposers respire and make CO2 available to plants. hopefully won't get negatively marked for that haha.....

Reply 1415

khimmy

Original post by leo123

even if you worked out heterozygous, you must have worked out recessive alleles and dominent so you might get 1 mark probably :smile:

for some reason i don't think so because its only two marks and all you had to do was square the number given and times in by a 100 to give the % so .. and its AQA we're talking about their always specific to the mark scheme lool

Reply 1416

woods.vanessa

I wrote NAD instead of NADP in the very last question :0
Do you think I'll loose 1 or 2 marks for that or more?!?!

Reply 1417

khimmy

hey can i just ask what did people get for the genotypes in the black, chocolate and cinnamon fur..??
i got :
black = Bb
Chocolate = Bb(small i)
Cinnammon- b(small i) b (small i)