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Ren_9
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#1241
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#1241
(Original post by REGA91)
What was the very last question of the paper? I'm starting to worry that I missed it too! It's all such a blur
It was how agricultural systems increase net productivity in livestock from what I remember.

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REGA91
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#1242
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#1242
(Original post by Ren_9)
It was how agricultural systems increase net productivity in livestock from what I remember.

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Yay, I did remember it! What a relief Thank you
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hannah2101
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#1243
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#1243
Has anyone made and unofficial mark scheme with all of the questions on it and the marks available for each questions?
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akat
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#1244
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#1244
(Original post by Starlight94)
I did 2 x 0.03 x 0.97 and got 5.82 or something :/
Thats what I got too!
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AtomicSeahorse
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#1245
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#1245
What did people put for the question asking 'what is the evidence from the diagram that Tay-Sachs isn't on the X chromosome?!
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4MANU4EVER4
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#1246
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#1246
(Original post by AtomicSeahorse)
What did people put for the question asking 'what is the evidence from the diagram that Tay-Sachs isn't on the X chromosome?!
I can't remember the actual child numbers, but the main gist was to say that both a male and female child, who were siblings, had the disease.
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safis
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#1247
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#1247
(Original post by br13)
hahaha yes, spelt the one beginning with G - ginvinigus or whatever - wrong every single time and kept having to correct it
Lool me too! Did anyone else finish like 30 minutes early?
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madkyoshi
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#1248
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#1248
Hopeless simply hopeless!!

Biology can be so unpredictable.

Last time in this exam I was jumping around yes I did so great guess what. Got a D :confused:

And another girl from my class was so depressed about how bad it went. Guess what she almost got :eek:A*
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madkyoshi
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#1249
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#1249
(Original post by safis)
Lool me too! Did anyone else finish like 30 minutes early?
I finished right on spot when they said ok your time is finished..

They say when you find it to easy then it maybe that you are doing it wrong
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safis
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#1250
(Original post by madkyoshi)
I finished right on spot when they said ok your time is finished..

They say when you find it to easy then it maybe that you are doing it wrong
Oh no I went back and answered the questions I left out. Hopefully we have done well. Off to study for biol5 now.
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Reina
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#1251
(Original post by AtomicSeahorse)
What did people put for the question asking 'what is the evidence from the diagram that Tay-Sachs isn't on the X chromosome?!
One of the males didn't have the disorder. If it was on the X chromosome that means the normal allele must have been passed on to all of his daughters so none of them would have the disorder (since the normal allele is dominant). But one of his daughters did.
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DavidYorkshireFTW
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#1252
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#1252
Hey people
Just out of interest was the exam easier or harder than it was in January?
For people who did retakes.
Hope it went well everyone
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TheFootyKing19
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#1253
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#1253
(Original post by DavidYorkshireFTW)
Hey people
Just out of interest was the exam easier or harder than it was in January?
For people who did retakes.
Hope it went well everyone
Both at the same level of difficulty tbh.

50 for an A me thinks
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biology.psychology
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#1254
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#1254
Has an unofficial Mark Scheme been made yet? or is everyone revising for biol5 lol?
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laser174572
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#1255
People have been asking about an unofficial marks scheme, building on what I posted earlier, here’s what I can gather from everyone’s contributions were the questions and possible marking points. Thanks to TheFootyKing19 in particular for his earlier post, from which I have incorporated some answers and who remembered a few more questions than I had done. Again feel free to copy and re post this with corrections/additions you feel are necessary.
NOTE: the actual marks scheme might be very different, you can never tell with AQA, this is just a guess/list of possible marking points!

1 a) What information is needed to calculate the growth rate of a population? (2)
- Birth and death rates
- Immigration and emmigration rate
OR
- Initial population
- Rate of population change


b) How does the graph show that it is in the early stages of a demographic transition? (2)
- Low life expectancy
- High death and birth rates

2 a) Which species is the pioneer? (1)
- U. Lactulana (something like that anyway)

b) Suggest why some scientists expressed concern that concrete blocks had been used in this study (2)
- Different mineral composition
- Not natural to the shoreline
- May not weather in the same way as rock
Not really sure on this one, "Suggest" questions are a bit difficult to predict what they're looking for

c) 2b Using the information in the graph, explain succession (4)
- Colonization of pioneer U. Lactulana
- Environment initially hostile so few species can survive
- Allows other species to colonize
- Which change the environment to make it less hostile and more stable
- Which allows other species which are more adapted to colonize
- Competition occurs, pioneer greatly decreases in number
- Biodiversity increases
- Stable climax community reached


3 (?) a) What is meant by phenotype? (2)
- Observable characteristics of an organism
- Resulting from both genotype and the effects of the environment/it’s interaction with the environment

b) i) What evidence from the pedigree chart shows that the condition is recessive? (2)
- Unaffected parents produce affected offspring
- Parents are therefore heterozygous

ii) What evidence from the pedigree chart shows that the condition is not X-linked? (2)
- Affected daughter from unaffected father
- Daughter would have to have two copies of the recessive allele, one from each parent, therefore the father would have the recessive allele and as males only have one X chromosome would be affected.

c) The rate of the condition in a population was 1 in 1000. What would you expect the percentage of heterozygous individuals to be? (3)
q^2 = 0.001, q = 0.0316, p= 0.9683, 2pq= 0.0612 = 6.12%

d) Use the information given to explain why the percentage of heterozygous individuals may be different to that calculated in c) after several generations (2)
- Affected individuals die as children/do not survive to reproduce/pass on the allele
- So allelic frequency decreases

4 (?) a) Tick boxes: X Y Y
X Y Y
Y Y Y
(Y represents a tick) (3)

b) Explain why glucose was not added to the isolated mitochonria (2)
- Glucose is not used in the link reaction
- Glucose broken down to pyruvate in the cytoplasm
- Mitochondria do not possess enzymes for glycolysis
- Glucose is unable to diffuse into/enter the mitochondria

c) Methanfate has a similar structure to succinate, explain how it inhibits the reaction involving succinate (2)
- Similar shape so complementary to the enzyme’s active site
- Acts as a competitive inhibitor
- Reduces number of enzyme-substrate complexes forming between the enzyme and succinate

d) Explain why the uptake of oxygen fell (can’t remember the exact context) (2)
- Oxygen acts as final acceptor in the electron transport chain
- Oxygen accepts protons and electron to form water
- As less reduced NAD and FAD available less electron transport occurs so less oxygen taken up

5 (?) a) Why was it important that the plants were kept in the same conditions for 10 days before the experiment? (2)
Anyone want to offer some marking points here? I put something along the lines of so at the start of the experiment they had equal amounts of TP

b) Explain why the plants were kept in the dark for the 6 hours before the experiment (2)
- No photosynthesis
- So have little TP/similar levels of TP at start of experiment (again, not sure, feel free to correct me)

I can’t remember the other parts of this question, I think they gave you some extra information and you had to explain the results in some way?
TheFootyKing19’s marking points seem to perhaps be right:
I ron deficiency - TP:
- less GP produced
- less TP produced
- less electrons excited in chlorophyll
- less ATP produce


6 a) Explain how fragmentation of the Amazon rainforest in the past led to high species diversity in the current day (5)
- Initially there is variety
- Due to mutation
- Geographic isolation as forest fragments.
- Different selection pressures
- Different alleles selected for, differential reproductive success
- Frequency of different alleles increases in the different populations.
- When the areas become linked once again the species are genetically isolated and can no longer breed - they are different species
- More plant species
- More habitats/niches/food sources
- Therefore more species of bird

b) Why does speciation not occur as often now?
- As members of a population are not isolated they can read freely
- Same selection pressures affect whole population (wasn't as sure about this one, if anyone has any ideas please edit and re-post)


7 a) Explain why lizards were taken from many sites (1) (might have been 2 marks?)
- So as sample is representative of the whole population

b) Suggest a method of ensuring that the sites were selected at random (2)
- Number the sites
- Use a random number generator

c) Explain why the percentage of lizards with malaria was used rather than number (2)
- Samples are of different sizes
- Allows comparison

Again I can’t remember the remainder of the parks of question 7, if anyone can remember them please add them! There should be 9 or 10 marks more of questions.

8 a) Describe the advantages of IPM (6)
- Minimises use of pesticides so minimises resistance
- Mechanical removal of pests minimises impact on non-pest species
- Biological aspect only requires one application and is specific
-Improved biodiversity
- Pesticides work instantly
- Biological agents slow
- Biological agents don't kill all of the pests
- Pesticides do
- Biological agents don't need to be continually applied
- Pesticides do
- Biological agents don't build up resistance
- Pesticides do
- reduces amount of pesticides that need to be sprayed
- minimizes risk to both humans and environment
- reduces risk of pests developing resistance
- increase crop productivity
- limits economic damage to agricultural system
- cheap to use - requires one application



b) Describe how nitrates lead to the death of fish in ponds and lakes (5)
- High nitrate concentration causes and algal bloom
- Blocks light
- Plants at the bottom of the pond/lake can no longer photosynthesise and die.
- Saprobiontic organisms decompose the dead plants
- These respire aerobically
- Oxygen concentration of the water falls
- Fish require high oxygen concentration and so die

c) Describe how intensive farming methods increase the productivity of livestock (4)
- Selectively bred for maximum productivity
- Kept in a warm environment to minimise amount of energy required to maintain body temperature and minimise respiratory losses
- Movement may be restricted to minimise respiratory losses, maximising energy available for growth
-Fed concentrate diets which are easily digested so minimum energy is lost in the faeces
- Given antibiotics to reduce the risk of disease


Also, to throw in my hat, I think that boundaries will be pretty similar to January, so around 62 for 100 UMS, 57 for A*, 52 for A, 47 for B, 43 for C, but I'm no expert!
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TH4RG3
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#1256
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#1256
For 4.b) you can also put glucose cannot diffuse through the mitochondria membrane

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laser174572
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#1257
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#1257
(Original post by TH4RG3)
For 4.b) you can also put glucose cannot diffuse through the mitochondria membrane

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Ah yes of course, edited to reflect this, thank you!
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Scienceisgood
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#1258
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#1258
I am fairly confident I have gotton at least a B in this paper which is what I need. =l
Going by these results, made some stupid mistakes though!
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khalidpatel
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#1259
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#1259
(Original post by laser174572)
People have been asking about an unofficial marks scheme, building on what I posted earlier, here’s what I can gather from everyone’s contributions were the questions and possible marking points. Thanks to TheFootyKing19 in particular for his earlier post, from which I have incorporated some answers and who remembered a few more questions than I had done. Again feel free to copy and re post this with corrections/additions you feel are necessary.
NOTE: the actual marks scheme might be very different, you can never tell with AQA, this is just a guess/list of possible marking points!

1 a) What information is needed to calculate the growth rate of a population? (2)
- Birth and death rates
- Immigration and emmigration rate
OR
- Initial population
- Rate of population change


b) How does the graph show that it is in the early stages of a demographic transition? (2)
- Low life expectancy
- High death and birth rates

2 a) Which species is the pioneer? (1)
- U. Lactulana (something like that anyway)

b) Suggest why some scientists expressed concern that concrete blocks had been used in this study (2)
- Different mineral composition
- Not natural to the shoreline
- May not weather in the same way as rock
Not really sure on this one, "Suggest" questions are a bit difficult to predict what they're looking for

c) 2b Using the information in the graph, explain succession (4)
- Colonization of pioneer U. Lactulana
- Environment initially hostile so few species can survive
- Allows other species to colonize
- Which change the environment to make it less hostile and more stable
- Which allows other species which are more adapted to colonize
- Competition occurs, pioneer greatly decreases in number
- Biodiversity increases
- Stable climax community reached


3 (?) a) What is meant by phenotype? (2)
- Observable characteristics of an organism
- Resulting from both genotype and the effects of the environment/it’s interaction with the environment

b) i) What evidence from the pedigree chart shows that the condition is recessive? (2)
- Unaffected parents produce affected offspring
- Parents are therefore heterozygous

ii) What evidence from the pedigree chart shows that the condition is not X-linked? (2)
- Affected daughter from unaffected father
- Daughter would have to have two copies of the recessive allele, one from each parent, therefore the father would have the recessive allele and as males only have one X chromosome would be affected.

c) The rate of the condition in a population was 1 in 1000. What would you expect the percentage of heterozygous individuals to be? (3)
q^2 = 0.001, q = 0.0316, p= 0.9683, 2pq= 0.0612 = 6.12%

d) Use the information given to explain why the percentage of heterozygous individuals may be different to that calculated in c) after several generations (2)
- Affected individuals die as children/do not survive to reproduce/pass on the allele
- So allelic frequency decreases

4 (?) a) Tick boxes: X Y Y
X Y Y
Y Y Y
(Y represents a tick) (3)

b) Explain why glucose was not added to the isolated mitochonria (2)
- Glucose is not used in the link reaction
- Glucose broken down to pyruvate in the cytoplasm
- Mitochondria do not possess enzymes for glycolysis

c) Methanfate has a similar structure to succinate, explain how it inhibits the reaction involving succinate (2)
- Similar shape so complementary to the enzyme’s active site
- Acts as a competitive inhibitor
- Reduces number of enzyme-substrate complexes forming between the enzyme and succinate

d) Explain why the uptake of oxygen fell (can’t remember the exact context) (2)
- Oxygen acts as final acceptor in the electron transport chain
- Oxygen accepts protons and electron to form water
- As less reduced NAD and FAD available less electron transport occurs so less oxygen taken up

5 (?) a) Why was it important that the plants were kept in the same conditions for 10 days before the experiment? (2)
Anyone want to offer some marking points here? I put something along the lines of so at the start of the experiment they had equal amounts of TP

b) Explain why the plants were kept in the dark for the 6 hours before the experiment (2)
- No photosynthesis
- So have little TP/similar levels of TP at start of experiment (again, not sure, feel free to correct me)

I can’t remember the other parts of this question, I think they gave you some extra information and you had to explain the results in some way?
TheFootyKing19’s marking points seem to perhaps be right:
I ron deficiency - TP:
- less GP produced
- less TP produced
- less electrons excited in chlorophyll
- less ATP produce


6 a) Explain how fragmentation of the Amazon rainforest in the past led to high species diversity in the current day (5)
- Initially there is variety
- Due to mutation
- Geographic isolation as forest fragments.
- Different selection pressures
- Different alleles selected for, differential reproductive success
- Frequency of different alleles increases in the different populations.
- When the areas become linked once again the species are genetically isolated and can no longer breed - they are different species
- More plant species
- More habitats/niches/food sources
- Therefore more species of bird

b) Why does speciation not occur as often now?
- As members of a population are not isolated they can read freely
- Same selection pressures affect whole population (wasn't as sure about this one, if anyone has any ideas please edit and re-post)


7 a) Explain why lizards were taken from many sites (1) (might have been 2 marks?)
- So as sample is representative of the whole population

b) Suggest a method of ensuring that the sites were selected at random (2)
- Number the sites
- Use a random number generator

c) Explain why the percentage of lizards with malaria was used rather than number (2)
- Samples are of different sizes
- Allows comparison

Again I can’t remember the remainder of the parks of question 7, if anyone can remember them please add them! There should be 9 or 10 marks more of questions.

8 a) Describe the advantages of IPM (6)
- Minimises use of pesticides so minimises resistance
- Mechanical removal of pests minimises impact on non-pest species
- Biological aspect only requires one application and is specific
-Improved biodiversity
- Pesticides work instantly
- Biological agents slow
- Biological agents don't kill all of the pests
- Pesticides do
- Biological agents don't need to be continually applied
- Pesticides do
- Biological agents don't build up resistance
- Pesticides do
- reduces amount of pesticides that need to be sprayed
- minimizes risk to both humans and environment
- reduces risk of pests developing resistance
- increase crop productivity
- limits economic damage to agricultural system
- cheap to use - requires one application



b) Describe how nitrates lead to the death of fish in ponds and lakes (5)
- High nitrate concentration causes and algal bloom
- Blocks light
- Plants at the bottom of the pond/lake can no longer photosynthesise and die.
- Saprobiontic organisms decompose the dead plants
- These respire aerobically
- Oxygen concentration of the water falls
- Fish require high oxygen concentration and so die

c) Describe how intensive farming methods increase the productivity of livestock (4)
- Selectively bred for maximum productivity
- Kept in a warm environment to minimise amount of energy required to maintain body temperature and minimise respiratory losses
- Movement may be restricted to minimise respiratory losses, maximising energy available for growth
-Fed concentrate diets which are easily digested so minimum energy is lost in the faeces
- Given antibiotics to reduce the risk of disease


Also, to throw in my hat, I think that boundaries will be pretty similar to January, so around 62 for 100 UMS, 57 for A*, 52 for A, 47 for B, 43 for C, but I'm no expert!
Integrated Pest Management: (this question did not ask advantages of bio control and pesticides):
- reduces amount of pesticides that need to be sprayed
- minimizes risk to both humans and environment
- reduces risk of pests developing resistance
- increase crop productivity
- limits economic damage to agricultural system
- cheap to use - requires one application

What was the question about??
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TH4RG3
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#1260
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#1260
For 5.a I said about allowing them to acclimatise or something

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