AQA BIOL4 - 13th June 2014 - Unofficial MarkschemeWatch this thread
Please contribute to the thread if you see any missing question. Obviously not all answers will be MS correct, that's why it's unofficial. Suggest questions on this paper were very unpredictable so their will be a very wide range of possible answers.
1. Describe two differences between the populations in 1700 and 2010 (2)
Mean number of children per woman lower in 2010.
Average life expectancy greater in 2010.
Suggest two reasons behind the differences you have described. (2)
Number of children per woman lower: increased access to birth control, more women educated
Life expectancy longer: improved healthcare, sanitation, more medicines, safer drinking water
Total population in 2011 (2)
60.2 million people
9.7 deaths per 1000 so 9700 per million so u do 9700*60.2 -----583940 deaths per 60.7 million
9.3 births per 1000 so 9300 per million 9300*60.2 ------559860 births per 60.7 million
60.7 million + 559860 - 583940 is 60175920
Nitrogen cycle question
2. Give two biological molecules with these components: (2)
Nitrogen: amino acids, proteins, urea
Phosphorus: DNA, ATP, RNA, phospholipid
Describe how nitrogen in dead organic matter is made available to plants. (3)
Proteins/amino acids broken down
Ammonia/ium converted to nitrites
Then to nitrates by nitirfying bacteria
Upwelling causes areas of high gross productivity. Explain why coastal areas have large fish stocks? (2)
Nutrients near surface, means that nutrients aren't limiting producers
Fish feeds on producers near surface in coastal areas??
3. What type of succession? (1)
(secondary) Succession - doubtful that secondary is needed as its not on spec.
What is there an increased diversity of birds in the woodland (3)
Increased diversity of plants
More variety of habitats/niches for birds
More variety of food sources for birds
Chickens genetics question
4. Explain why females are more likely to inherit sex-linked recessive allele. (1)
Females are XY and so cannot be carriers/only need one recessive allele instead of two it to be expressed.
Explain evidence from the diagram to show that the allele for rapid feather growth is recessive (2)
1+2 are unaffected yet produce affected offspring 5 so Individual 1 must be heterozygous/carrier. Note: Individual 2 was female so would be XY and could not be heterozygous as the gene was carried on X.
Give the genotype of the following chickens: (2)
Chicken 5: Xf Y
Chicken 7: XF Xf and XF XF
I thought their was two possibilities for Chicken 7, anyone else???
Give the genotypes of the parents who produce the following offspring: 2 rapid growing feather males and 2 slow growing feather females (1)
Genotypes: XFXf, XfY
Note: unsure of these genotypes, it's just what's been suggested in the thread
H-W equation calculation (3)
Square root of 0.04 = 0.2
1 - 0.2 = 0.8
2 * 0.8 * 0.2 = 0.32 * 100 = 32%
Sickle cell anaemia inheritance question
Explain why results are given as ratios (2)
Total number of patients varies
Allows for comparison between values
Describe how blood group affects chances of severe malaria (2)
Blood group A has increased chance + quote figures
Blood group O has 1:1 chance + quote figures
Not sure whether you needed to mention sickle cell trait here...?
Explain why population has gradually got less HbO genotype in comparison to HbC (3)
HbC have more chance of severe malaria/ more chance of death
Less HbO survive / More HbC survive
Less reproductive success
Increase in allele freq. of HbC / decrease in allele freq. of HbO
Photosynthesis graph question
6.Describe two other limiting factors (2)
Explain why CO2 can be used as a measure of net productivity (1)
CO2 taken up in photosynthesis, photosynthesis used to produce energy
Shaded plants is more adapted to low light intensity than shaded plant. Use the graph to explain why. (2)
In lower light intensities, less CO2 is released
More CO2 in stomata so more CO2 to combine with RuBP in low light intensities
Could mention compensation point & faster growth rate of shaded plant in low light intensities.
Anaerobic respiration of yeast question
7. Why a thin layer of oil (1)
Ensure no O2 from the flask reaches yeast, must ensure anaerobic conditions
b) Calculation (2)
Why does rate decrease between 50 and 60 seconds (1)
Glucose substrate used up
Repeat investigation to investigate aerobic respiration in yeast. What would happen to the amount of gas produced. (2)
Remains the same
O2 taken up for respiration (as it's terminal electron carrier)
Equal to CO2 produced
Why respiration in oxygen produces more ATP than without.(2)
Oxygen is a terminal electron acceptor. Without oxygen electron-transport-chain won't take place. Most ATP is made in ETC
Hydrilla - pest control question
8. Suggest two reasons why the Hydrilla is dominant? (2)
Wide variety of answers for this as it's a "suggest" I presume you have too guess characteristics of Hydrilla which makes it outcompete others:
Outcompetes others for light - can photosynthesise at a greater range of light intensities
Outcompetes others for nutrients - has a larger root system so can absorb more nutrients
Suggest two economic consequences of hydrilla.(2)
Again answers depend on AQAs mark scheme:
Hydrilla outcompetes the natural freshwater fishes food source, so natural fish die, less income in fish industry :/
Cost of having to remove/control hydrilla
Use a fungus as a biological control to Hydrilla. Fungus cultured from tissue of hydrilla in the origin country of species. Why is this form a fungus used? (2)
Specific to hydrilla
Hydrilla can't develop resistance?
Can't become a pest itself because can't survive on other species?
Why reheating/measuring cycle is a reliable way to measure biomass (2)
Removes water so you get dry mass
Reheating until mass is constant.?
Why only use 5 concentration of the pesticide (4)
Any less and the biomass of the hydrilla still increases
Any more and it would become:
not cost effective
may not biodegrade?
Why was a control used (1)
To make sure any effects on the biomass of Hydrilla was due to the treatments used
Why use integrated pest control system useful in this scenario? (2)
Apply the pesticide, pesticide reduces the levels to low numbers
Biological control begins working after lag time, this maintains populations at these low numbers in the long term.
Longer answer/factual recall questions
9. Explain how the LIR reactions use CO2 to produce organic substances. (6 marks)
Calvin cycle - in stroma
CO2 diffuses in through stomata and enters stroma
Combines with RUBP using an enzyme
This produces 2 molecules of GP
ATP and reduced NADP from LDR are used to reduce the GP into TP.
The NADP reformed goes back to LDR to be reduced again
Some TP is converted into useful organic substances e.g. glucose
Most TP is used to regenerate RuBP using ATP from LDR
Explain how human activities have led to global warming.(4 marks)
Less CO2 taken up in photosynthesis
Burning of felled trees
CO2 released into the atmosphere
Methane produced during decay/farming
CO2 and methane are greenhouse gases
Contribute to greenhouse effect so more infrared radiation reflected back to earth
Increased global temperatures
Explain how you could estimate the population size of bluebell population. (5 marks)
Map the area using grid
Use random number generator on calculator/computer to choose coordinates
To ensure sample is unbias
Place quadrat at coordinates
Measure abundance - frequency
Then calculate (No. of quadrat used / total area) * Avg. no of species per quadrat
Use running mean to make sure you have done enough samples
Do enough samples for statistical test
My grade boundary predictions:
I thought this paper was similar to June 2013, perhaps a bit easier...
A* = 58
B = 48
C = 44
D = 39
E = 35
The one about the biological molecules.... Im guessing phosphate is not a biological molecule which contains phosphorus :/
Contains Phosphorous: ATP ?
a) was molecules containing nitrogen and phosphate
b) use of microorganisms in breaking down dead matter into nitrates
can't remember the rest
I stupidly talked about less respiration ....... was it 2 or 3 marks?
I thought you do BR--DR which is -0.4 and then do 60200000/1000 <<and with that answer multiply by -0.4 then with this answer << deduct it for 60200000 to get 60152790 or whatever it was 60 million and something