UNOFFICIAL MARK SCHEME: AQA A Level Biology 20/06/2017 Paper 2

A special thanks to @DrNippleson for helping out with their contributions! :awesome:

This thread is for paper 2! There have been a lot of people asking for this thread, and of course I'm delivering! Like before, I don't really remember many of the questions so I'm calling all Biology students to contribute whatever they can to help us all out! :h:

Also, potential essay topics for paper 3 (based on what has already come up) - again, please feel free to come up with your own:
-Biology importance of cycles (Krebs, Calvin, Nitrogen etc.)
-Biological importance of ions (Kidneys and nerve impulses didn't come up much)
-Importance of transport (Haemoglobin, Plant transport, Mass transport like heart)
-Importance of proteins (structural proteins, ADN replication, protein synthesis, antibodies, transport across membranes, photosynthesis, digestion
-Pressure and pressure gradients, eg tissue fluid, the phloem, heart, lungs, nephron

Like before, press the "show" button below to see what we've already got!

Spoiler

(edited 6 years ago)

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Reply 1

SK20

Original post by Amefish

Like before, press the "show" button below to see what we've already got!

Spoiler

I talked about the chemoreceptors detecting a decrease in O2 (as it is used in aerobic respiration)- would that also get the marks?

Reply 2

Synesthesia

Original post by Amefish

Like before, press the "show" button below to see what we've already got!

Spoiler

q.1 (4 marks) Running causes an increase in heart rate. Describe the role of receptors and the nervous system in this process

*Increased Muscle Respiration
*Higher conc CO2 in blood
*Chemoreceptor in cartoid artery detects this
*Nervous impulse to Sympathetic nervous system in Medulla Oblongata
*Increased frequency of nervous impulses to SAN
*Higher frequency of waves of excitation released
*Higher Heart rate

The Transgenic Mosquito one was:

*Add more to population as offspring die before reproducing, so to prevent population size increasing as allele becomes extinct b/c not passed on, external supply of allele is provided in the form of transgenic mosquitos.

The 74/75 one was:

One was young, AD was not yet onset - thus not yet potential AD.

Reply 3

Synesthesia

Population one was:

((1*2*60*24*365.5)/5400000) * 100 = 19.5%

Reply 4

mstrcvk

Hardy Weinberg was 32%

AMPK allows fatty acids into mitochondria to be used as a respiratory substrate

Sympatric speciation, either different flowering times lead to genetic drift, or extra chromosome during reproduction leads to speciation

PCR stopped because it ran out of nucleotides

The diagram with certain genes inhibiting others (white>yellow>green) was an example of epistasis

Reply 5

SK20

Phenotype ratio for white : green : yellow was 2 : 1 : 1

Reply 6

saltatrixi1999

it gave you the actual diameter of your field of view and said there were on average (12?) cells per field of view and then you had to calculate the average diameter of one cell
i got 84um but who knows lol

Reply 7

d010534

Original post by Synesthesia

Population one was:

((1*2*60*24*365.5)/5400000) * 100 = 19.5%

I was so worried!! That's what I got but then everyone said something different at school lol

Reply 8

SK20

Original post by saltatrixi1999

I think I got that too :smile:

Reply 9

saltatrixi1999

Original post by d010534

I was so worried!! That's what I got but then everyone said something different at school lol

i also got 19.5 !!

Reply 10

Synesthesia

Original post by SK20

I think I got that too :smile:

It was 84.10

(Area)/Pi = R^2

sqrt(r^2) = r

r*2 = d

d/15 = mean

mean (mm to um) * 1000 = 84.10

Reply 11

SK20

Original post by Synesthesia

It was 84.10

(Area)/Pi = R^2

sqrt(r^2) = r

r*2 = d

d/15 = mean

mean (mm to um) * 1000 = 84.10

Yesss that looks familiar :h:

Reply 12

brumtown0121

blud i got the first one wrong ffs, i said acetylcholine, parasympathetic neurone ffs

Reply 13

Synesthesia

Sympatric - Reproductively seperated in same ecosystem (Ecological Immobility)

* No gene flow between populations
* Mutation occurs
* Increases chance of survival to reproduce
* Offspring with beneficial allele produced, differential reproductive success continues
* Allele frequency increases
* This mutation occurred in both populations
* Populations diverge to the point of being different species as allele frequnecy changes

Reply 14

gabby1410

predictions for paper 3?

Reply 15

joshcurtis1999

Original post by mstrcvk

would i have got the mark for putting dominant epistasis?

Reply 16

Synesthesia

Original post by joshcurtis1999

would i have got the mark for putting dominant epistasis?

They mark using the list principle so it's a toss up.

Edit: Probably not - the first inhibition was by passive alleles.

Reply 17

joshcurtis1999

Original post by saltatrixi1999

yeh i got 84 aswell

Reply 18

buzz1234

Original post by SK20

I think I got that too :smile:

was 15 and i got 83.3 micrometers

Reply 19

Deutschmaster99

For the iPS cells in mice evaluate the effectiveness in human I talked about how the transplant was successful in mice as after the first week there was similar blood glucose levels to non diabetics however for mice it showed more fluctuations than the non diabetic group. However since it was done in mice, although mice are mammals like humans, there are possible unknown side effects in humans or the treatment may not be effective in human as the transplant cells may be rejected by the immune system and the long term effects are not known in humans so further tests needed.

For the why the pancreas transplant shouldnt be used for type II diabetes I said type II can be treated with regular exercise and diet so no need to risk surgery. Other point was that in type II the beta cells still produce insulin but insulin receptors are damaged so would be ineffective