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!