AQA GCSE Biology Unit 2 - 24th January 2012 Unofficial Markscheme

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Original post by -AmusingUsername-

For 4b, instead of magnesium ions I answered "nitrates". I thought that a deficiency in nitrates AND magnesium ions caused a yellow discolouration of leaves.

http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/greenworld/plantmineralsrev1.shtml

:iiam:

SO glad its not just me that thought that..

Can anyone shed any light?

Reply 61

Math12345

Original post by MattDowse

SO glad its not just me that thought that..

Can anyone shed any light?

Bitesize has many mistakes, so i wouldn't recommend it. The answer is Magnesium.

Reply 62

Benjaminooo

Original post by Math12345

Bitesize has many mistakes, so i wouldn't recommend it. The answer is Magnesium.

My biology teacher said Magnesium as well

Reply 63

Dominic101

Original post by Benjaminooo

43 or more - You have to be very close to the top really - In the ISA I believe 39+ got you full UMS.

Even in this exam?

Reply 64

Benjaminooo

Yeah I think so - isn't it normally like 97%+ to get full UMS points?

Reply 65

Dominic101

Original post by Benjaminooo

Yeah I think so - isn't it normally like 97%+ to get full UMS points?

That doesnt sound right considering you needed 29/45 for 100% ums for the last biology b2

Reply 66

Benjaminooo

Original post by Dominic101

That doesnt sound right considering you needed 29/45 for 100% ums for the last biology b2

Oh right, I thought 100% UMS was a really high mark, but I could well be wrong.

Reply 67

Thames

just to clear up any questions... ums is based on on how well everyone else does:
if the paper was hard --> everyone does worse --> lower grade boundaries
easy paper--> everyone does well --> ghigher grade boundaries
however, many ppl that b2 in june are resitting students so grade boundaries are much lower than in january
so for jan 2012 everybody found it hard so its extremely likely for their to be low grade boundaries... how low i don't know, i don't think the paper has been this hard in b2 history. aqa will release the grade boundaries the day before the exam (7th march)

Reply 68

Thames

Original post by Thames

sorry i meant results

Reply 69

nooraaa

for the disputed answer of 1b i put 10. the reason for this is because it asked for the MAXIMUM safe time and a person can stay out for 9.5 mins and still be safe so it can't be 9 minutes.

Reply 70

Marcus6189

For 100 UMS on this paper I'd say it'd be about 30? ( normally around 4 marks above the grade boundary for an A* ) This was a difficult paper no matter what anyone says, so a 26 A* seems reasonable. Also an ISA mark cannot be compared to this, ISA marks are far higher than Module results.

Also as for the disputed question in which some people are saying the answer is 5 - 10 I'm pretty sure that ( considering it was one of the first questions ) it will not have a complicated answer and when the examiners see how badly worded the question was they'll give any answer between 5 - 10. Just what I think.

Reply 71

emily_p3

4a. I put something along the lines of: The amount of carbon dioxide used up on day 1 was less than day 2 (1?)so it shows that Light must have been the limiting factor(2?) as less carbon diode was used up in photosynthesis(3?).

Reply 72

emily_p3

Original post by Math12345

AQA GCSE Biology Unit 2 Unofficial Markscheme

1.
a. As you decrease the temperature the time taken to get the frostbite decreases (or you get frostbite more quickly). (1)
b. 9 or 10 minutes. (1) This was confusing, because it could be anywhere between 9 and 10. People are saying it is 5?
c. Shivering and constriction. (2)

2.
a. Control variables: mass of crushed apple / amount of drops of liquid. (1) There are more possibilities.
b. The drops can be different sizes. (1)
c. Amylase does not break down the cell wall like water. Pectinase enzyme digests the cell wall. Energy in boiling water causes the cell wall to break apart. (3) Improvement?
d.
i. 11.6 cm^3 (1) Not sure...
ii. Pectinase enzyme is denatured at high temperatures, but boiling the apple still has the same effect. (2) Improvement?

3.
a. Drug B - Kills pancreatic cells which means even less insulin is produced than before (which is why it only has negative effect on some diabetics). (2) Improvement?
b. Careful attention to diet and pancreatic cell transplants (2) There are more possibilities.
c. The insulin enzymes are destroyed by the digestive system or the insulin in the tablet would not reach the blood (1) Improvement?

4.
a. Cloudy means less light so less photosynthesis so less CO2 used. (2) Improvement?
b. Magnesium. (1)

5.
a. (45/25,000)*100=0.18% (2)
b. Heat. (1)
c. Shorter food chains more efficient as there are less energy losses. Heron only gets 2 out of the 25,000kJ of energy absorbed. (2) Improvement?
d. Microorganisms consume the dead animals and plants causing decay. They then used the biomass for respiration which released carbon dioxide into the atmosphere - replacing CO2. CO2 then used in photosynthesis to be returned to the food chain. (3) Improvement?

6
a. Water moves through the partially permeable membrane by osmosis from the dilute solution to the more concentrated sugar solution causing the solution level to rise. (3) Improvement?
b. Would still increase, but at a slower rate the solution is less concentrated so smaller concentration gradient. (1) Improvement?

7
a.
i. Gene. (1)
ii. Ribosomes. (1)
b. A combination of three bases codes for different amino acids. Amino acids then join together to create the protein which codes for blue eyes. (3) Improvement?
c.
i. Different amino acids in structure. (1) Not sure...
ii. Different coloured eyes. (1) Not sure...

8. (5)
Adult bone marrow - Advantages
Does not kill embryos (1)
It is a simple operation (1)
Can still cure heart and blood diseases (1)

Adult bone marrow - Disadvantages

Embryonic stem cells - Advantages
Is not painful to patient (1)
Can develop into any type of cell so can cure more diseases (1)

Embryonic stem cells - Disadvantages

Conclusion (1)

For Question 7cii i put that there would be a change in characteristics, what do you think?
Also for 1b a lot of people have being saying it had to be less than 10 otherwise the person would have frostbite already which is annoying as i put 10.
what are your thoughts on these?

4a. I put something along the lines of: The amount of carbon dioxide used up on day 1 was less than day 2 (1?)so it shows that Light must have been the limiting factor(2?) as less carbon diode was used up in photosynthesis(3?).

Reply 73

sjrahman

I gave myself 30-33 marks... roughly what grade would that be

Reply 74

sjrahman

Original post by MattDowse

SO glad its not just me that thought that..

Can anyone shed any light?

Bitesize screwed you lot over lol, during the exam i remembered that my revision guide said nit=stunt yellow=mag... a very odd way to remember but it worked