# AQA Biology B2 - Unofficial Mark Scheme

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• View Poll Results: What do you predict your score?
< 10%
3.14%
> 10%
0.42%
> 20%
1.68%
> 30%
3.35%
> 40%
4.72%
> 50%
6.50%
> 60%
14.47%
> 70%
23.58%
> 80%
28.93%
> 90%
10.38%
100%
2.83%

1. (Original post by clorenzoni5)
wasnt it supposed to be 1 min? since the heart rate stays high for a bit after u exercise, before it decreases?
I thought it just levelled off at 1.5 and carried on for a bit and then reduced but as it it climb higher than 1.5 I though the athlete was just paying back the oxygen debt
2. (Original post by WrightKe)
So why was the answer Mitosis? I'm so confused, maybe I misread the question.
Process in the image was Meiosis. The zygote divides many times by mitosis to form an embryo (which is what the bottom question asked).
3. (Original post by Certified)
Process in the image was Meiosis. The zygote divides many times by mitosis to form an embryo (which is what the bottom question asked).
I swear it said how's does a fertilised egg replicate it self?
4. (Original post by Cakes717)
That's what I got? But everyone is saying something about converting...
This is roughly what I got. I now realise the size of the quadrat was in cm
6. Doing 20/10
only found the mean amount of plantains per 0.625m^2 not per m^2 which was why the answer per metre^2 was 3.2 I think
7. I didn't put any values for the 6 marker, i just talked about the same intervals and stuff.. Agh
8. (Original post by Door105)
I got 2 whats the right answer
I put 1
9. (Original post by Edgerulezs)
Sameee 😂😂 we're either smart for doing that or overthought things 😭
I'm hoping you're smart because I put 1 too 😂😂 it said that lactic acid built up so I thought it'd remain the same for a little while to pay back the oxygen debt?
10. (Original post by Blahblahblah7)
I swear it said how's does a fertilised egg replicate it self?
A zygote is a structure that forms when a sperm fertilises an egg. A zygote containing eight identical cells. The zygote then divides many times by mitosis to form an embryo. The first division of the zygote forms two cells, the next four, the next eight, and so on. Up to the eight-cell stage, all of the cells are identical. They are called embryonic stem cells. It is possible for embryonic stem cells to develop into any other specialised type of cell that the growing embryo needs - for example, nerve cells, blood cells and muscle cells. However, once the embryonic stem cells become specialised, they can't change into any other type of cell.The specialised cells can form all the different types of tissue that the embryo needs.
wait there was one for enzymes??
The only question I saw on enzymes was 'what is an enzyme'- don't know why people are putting advantages and disadvantages?

And then there was the advantages and disadvantages of hydrogen peroxide and catalyst which gave the the text to answer from. Is this correct?
12. Any thoughts for Grade boundary
13. (Original post by Wisbey)
I was wondering this so put the poll at the top. Looks like people are pretty confident so they will be quite high.
14. Wait was was the answer for question 7 than, was it mitosis or meiosis
15. 1a. without (sufficient) oxygen
1aii. ran for 1.5 minutes
1b. The amount of lactic acid produced increased. Lactic acid is a product of only anaerobic respiration.

3. what is an enzyme?
A biological catalyst that speeds up chemical reactions by lowering the activation energy needed for the reaction to take place, without being changed or used up during the reaction.

circle question - cytoplasm

5. Chance of getting polydactyly was 50%
the mass of the gametes:
a - 6.6
b- 13.2
c and d - 6.6
the ones at the end of telophase II - 3.3

6. Advantage: Reaction can take place at lower temperatures - less energy used so lower heating costs
Disadvantage: Doesn't kill pathogens/ catalase then contaminates the milk

8. The foxes could mate successfully and they have similar physical features

The foxes may have been isolated into different populations due to higher sea levels. The conditions on each island may have been different. All the foxes in each population would have shown genetic variation (due to sexual reproduction and mutations). Natural selection would have acted differently in the different populations. Foxes with favourable alleles passed on these alleles to the next generations, Eventually the different populations would not be able to mate to produce fertile offspring - speciation had occurred.
16. (Original post by Lolol786)
Unofficial marks scheme (may not be correct ) not in order
Anerobic - incomplete breadown of glucose
How can u tell ?- athlete produces lactic acid
Athlete and blood flow to muscles - oxidation of co2 and lactic acid , faster transportation of oxygen into blood streem , causes muscles to contract , athlete then anerobicly respires which decreases blood flow to muscles - muscle fatigue

Epithelial - covers and protects stomach from acid
Muscular contracts and churns up food
Glandular secretes hormones and digestive juices to increase breakdown of food
Fox question - isolation, adaption,natural selection , mutation, unable to breed
Can't Remeber anymore
What was the answer to the genetic diagram question?
17. (Original post by GCSE_core)
The only question I saw on enzymes was 'what is an enzyme'- don't know why people are putting advantages and disadvantages?

And then there was the advantages and disadvantages of hydrogen peroxide and catalyst which gave the the text to answer from. Is this correct?
yeah thats the only one i saw too, and yepp i used information from the text they gave us.
18. Can anyone actually explain the genetic diagram part, maybe draw it out and fill in the answers please?

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19. (Original post by Certified)
A zygote is a structure that forms when a sperm fertilises an egg. A zygote containing eight identical cells. The zygote then divides many times by mitosis to form an embryo. The first division of the zygote forms two cells, the next four, the next eight, and so on. Up to the eight-cell stage, all of the cells are identical. They are called embryonic stem cells. It is possible for embryonic stem cells to develop into any other specialised type of cell that the growing embryo needs - for example, nerve cells, blood cells and muscle cells. However, once the embryonic stem cells become specialised, they can't change into any other type of cell.The specialised cells can form all the different types of tissue that the embryo needs.
So is it mitosis?
yeah thats the only one i saw too, and yepp i used information from the text they gave us.
People are writing about it not denaturing and lowers the cost etc but that wasn't in the text was it?😬

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