# BIOL4 Biology Unit 4 Exam - 13th June 2011 watch

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1. (Original post by tehsponge)
What do you all reckon the last 5-6 mark questions will be this year?
I have a feeling eutrophication will come up as one of them.
I hope not I hate the Nitrogen Cycle ><
2. (Original post by 30DiedOnMars)
I hope not I hate the Nitrogen Cycle ><
Same. But I find eutrophication easy since I did it at GCSE as well (in the same detail), so I really hope they stick it in somewhere...
3. (Original post by xbabycakes)
it's tomorrow guys.. oh my god
I knowww..
Dunno which part to revise! Its like we know everything but thats not we are gonna be asked about!

Ive done some past papers, revised all chapters but still !!

ANyone got question pack for conservation and poulation?!?!?
Wish I was doing OCR
4. (Original post by SK-mar)
this may sound stupid so sorry lol - but during which process is CO2 produced during anaerobic respiration?? Is it the bacteria (yeast) that convert pyruvate into ethanol for plants? do they respire it, but if so how?
Remember fermentation in chemistry !(well, if you do :P)

Glucose==> 2 co2+ 2 ethanol
5. (Original post by GdotNizzle)
Well through trial and error method, i found:

let x = 125/4.1,

((x*100)/13.1)*100= 23,273 but thats just a random answer

oh yep i think i get this actually.

so (125/4.1) x 100 = total amount of energy passed onto bullock.

total amount of energy passed onto bullock = 13.1 % = energy in grass. however to find energy of photosynthesis we need to know the value for 100% .... so you do (3049/13.1) x 100 = 23274 .....

thanks btw...
6. (Original post by arvin_infinity)
Remember fermentation in chemistry !(well, if you do :P)

Glucose==> 2 co2+ 2 ethanol
yep i recognise this now! cheers bro.
7. Eutrophication- should guarantee all the marks I think.

- Run off/leaching of nutrients leads to increase growth of algae
- This leads to plants and algae to grow exponentially
- Most algae grow at the surface and the upper layers become densely populated with algae.
-Light is limiting the growth of plants and algae at lower levels which die.
- The lack of dead plants and algae no longer limits saprobiotic organisms which grow exponentially using dead organisms as food.
- They create a demand for oxygen and aerobic organisms such as fish. They die as oxygen is used up.
- Anaerobic organisms increase as there is no competition. They decompose dead material, releasing nitrates and toxic waste.
8. (Original post by tehsponge)
Same. But I find eutrophication easy since I did it at GCSE as well (in the same detail), so I really hope they stick it in somewhere...

- soluble fertiliser (nitrates) leached into nearby water sources (eg. pond or river)
- nitrates stimulate algae and cause an algal bloom on the surface of the water
- blocks light from photosynthesising plants below, so they cannot photosynthesise as light is needed and die
- microorganisms digest their dead organic matter, and in doing so respire aerobically using O2 and producing CO2
- dissolved oxygen levels in water are used up by respiring microorganisms, so fish and other aquatic organisms cannot aerobically respire sufficiently and die.

I have a feeling this may come up as its hasn't yet!
9. (Original post by SK-mar)

- soluble fertiliser (nitrates) leached into nearby water sources (eg. pond or river)
- nitrates stimulate algae and cause an algal bloom on the surface of the water
- blocks light from photosynthesising plants below, so they cannot photosynthesise as light is needed and die
- microorganisms digest their dead organic matter, and in doing so respire aerobically using O2 and producing CO2
- dissolved oxygen levels in water are used up by respiring microorganisms, so fish and other aquatic organisms cannot aerobically respire sufficiently and die.

I have a feeling this may come up as its hasn't yet!
Also the level of aerobically respiring microorganisms decreases due to the decrease in O2 levels, leading to an increase in anaerobic microorganisms as there is less competition for food. Anaerobic microorganisms cause the water to go putrid by producing toxins and hydrogen sulfide.
10. what is meant by the term statistically significant
11. Hi guys, I was wondering whether you guys could tell me - what year was it when everyone made a big deal of the biol4 paper and it made the news cos it was so hard???
My friend told me it was jan2010 cos it was all about shrimps, however I am doing the jan 2010 paper now - and a shrimp question hasnt come up! its not that bad :/ x
12. Okay I am seriously stuck on the Hardy-Weingberg calculation on the June 2010 paper. Question 3d. http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN10.PDF

I think there is a mistake on the mark scheme. They tell you that the allele for long hair (h) is recessive. So the only cats with long hair will be hh. They give you the frequency of this as 0.33. So 0.33 should be the value of q^2 right? The mark scheme says 0.33 is q.

Mark Scheme:
Two marks for correct answer of 44(.22);;
One mark for incorrect answer in which p/frequency of H
determined as 0.67 and q/frequency of h as 0.33
OR

EDIT: I just realised the table heading says: "Frequency of allele" not frequency of phenotype
13. (Original post by *QueenBeee)
Hi guys, I was wondering whether you guys could tell me - what year was it when everyone made a big deal of the biol4 paper and it made the news cos it was so hard???
My friend told me it was jan2010 cos it was all about shrimps, however I am doing the jan 2010 paper now - and a shrimp question hasnt come up! its not that bad :/ x
I think it was the infamous shrew question? Maybe your friend meant shrews not shrimps.
14. (Original post by INeedToRevise)
Eutrophication- should guarantee all the marks I think.

- Run off/leaching of nutrients leads to increase growth of algae
- This leads to plants and algae to grow exponentially
- Most algae grow at the surface and the upper layers become densely populated with algae.
-Light is limiting the growth of plants and algae at lower levels which die.
- The lack of dead plants and algae no longer limits saprobiotic organisms which grow exponentially using dead organisms as food.
- They create a demand for oxygen and aerobic organisms such as fish. They die as oxygen is used up.
- Anaerobic organisms increase as there is no competition. They decompose dead material, releasing nitrates and toxic waste.

Yeah i think that would get the 5 marks...altho i would actually refer to it as nitrates instead of nutrients
15. (Original post by ben10)
what is meant by the term statistically significant
determines the probability of the results being due to chance
16. can someone explain anearobic resp to me please
17. (Original post by tehsponge)
Okay I am seriously stuck on the Hardy-Weingberg calculation on the June 2010 paper. Question 3d. http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN10.PDF

I think there is a mistake on the mark scheme. They tell you that the allele for long hair (h) is recessive. So the only cats with long hair will be hh. They give you the frequency of this as 0.33. So 0.33 should be the value of q^2 right? The mark scheme says 0.33 is q.

Mark Scheme:
Two marks for correct answer of 44(.22);;
One mark for incorrect answer in which p/frequency of H
determined as 0.67 and q/frequency of h as 0.33
OR
No mark scheme is right, we did this as a mock in class

0.33 is frequency of the allele, not the genotype, and so is q

0.33 x 0.33 = q2 = 0.1089

p = 1 - 0.33 (q) = 0.67

0.67 x 0.67 = 0.4489 = p2

heterozygous = 2pq in the formula p2 + 2pq + q2 = 1

so 2pq = 1 - (p2 + q2) = 2pq 1- (0.4489 + 0.1089 ) = 0.4422 = 2pq
18. (Original post by ben10)
can someone explain anearobic resp to me please
in anaerobic only glycolosis happens because of the absence of oxygen. It produces less ATP. In plants the pyruvate is reduced to ethanol by getting the hydrogen ions from the NADH, this way NADH is recycled so NAD is provided for glycolosis again and also Co2 is released, if this didn't happen then no ATP would be produced. In animals the pyruvate is converted to lactate.
19. (Original post by ben10)
what is meant by the term statistically significant
The probability of the results being due to chance is 0.05% or less, therefore, results are significant and not due to chance.
20. (Original post by *QueenBeee)
Hi guys, I was wondering whether you guys could tell me - what year was it when everyone made a big deal of the biol4 paper and it made the news cos it was so hard???
My friend told me it was jan2010 cos it was all about shrimps, however I am doing the jan 2010 paper now - and a shrimp question hasnt come up! its not that bad :/ x
Yep it's the shrew question. I didn't find it that bad either.

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