In this bundle there are more than 5000 aqa a level biology questions and if you do every question and memorise the mark scheme you will get that A* without a doubt
1. (a) Allow two marks for 617;
allow one mark if arithmetical error in calculation; 2
(b) (i) Moose numbers rose in absence of predators / with plenty of food;
depletion of food / spread of disease / climatic change /
resulted in fall / death; 2
(ii) Caused the moose numbers to stabilise at lower level / equivalent; 1
[5]
2. (a) Release ammonia / ammonium / ammonification;
BY Decomposers / putrefying / saprotrophic / ammonifying bacteria;
ammonia nitrite nitrate / nitrification;
BY nitrifying bacteria / named bacteria; max. 3
(b) (Interspecific) competition;
for nitrates / nitrites / ammonia / ammonium compounds; 2
[5]
[Process is stand alone - bacteria only credited if in correct context.]
3. (a) (i) All (living) organisms/populations found in an ecosystem/in a habitat/in an
area; (NOT just ‘all species present’/’no. of spp.’) 1
(ii) Habitat (/environment) + community (/described)/
abiotic and biotic factors in a defined area/named area; 1
(b) (i) 9 – 25°C 1
(ii) biotic factor: food/predators/presence of mate/competition/
disease;
abiotic factor: water current/tides/nature of substratum/O2 (conc) /
pH/toxins/light; 2
[5]
4. (a) Wood mouse; 1
(b) Decomposers/bacteria/fungi/saprophytes/saprotrophs/detritivores; 1
(c) Colonisation/pioneer species/examples from fig/seeds/fruits;
soil formation/improvement/change by organism;
succession/eq;
process repeated to climax community/forest; max. 3
diversity is reduced;
(d) {trees form food source for many species/wide range of primary consumers;
{(primary consumers/named example/are eaten by other species)
{idea that trees are the basis of food chains/food webs;
productivity of area is reduced (with loss of trees);
so fewer organisms can be supported;
habitats are lost/ecological niches are lost (with each tree species lost); max. 3
[8]
Sir George Monoux Sixth Form College 1
,5. (a) (i) All the organisms present in an area / all populations in an
area / populations of all species in an area / in an ecosystem;
NOT “all the species in an area”
(ii) Habitat + community / environment + organisms / all biotic
and abiotic factors of an area; 2
(b) (i) EITHER: More light;
More photosynthesis / fewer spp. adapted to
lower light;
OR: Warmer;
Faster metabolism / named aspect; 2 max
(ii) ‘It’ / south-facing is less hostile environment / conditions better /
favourable for plants;
Has higher (index of) diversity / more species present;
Provides more niches / described / more complex interactions
between species;
Changes in abiotic factors / named example have less influence;
Loss of one species will have less effect on food web / on the
system; 3 max
(iii) Greater variety of habitats / described – e.g. re. nesting sites /
humidity / temperature / more food / more variety of food types /
less competition for food / more niches; 1
(c) (i) EITHER: Correct answer: 280 (2 marks) ;;
OR: Correct use of data but wrong answer/
P = (40 x 42) ÷ 6 / correct formula (1 mark) ; 2 max
(ii) Sample too small / too few traps / too short a time to mix evenly;
Uneven distribution of animals / great variation trap to trap;
Birth / death of some woodlice;
Immigration / emigration;
Marking method affected woodlouse behaviour; 2 max
[12]
6. (a) (i) B – higher standard deviation; (extras CANCEL) 1
st
(ii) 1 : A (no mark)
nd
2 : Limpets have smaller H/W / smaller mean;
Limpets have (relatively) large foot area;
Better grip on rock; 3
(b) (i) Need representative / ‘typical’ / ‘reliable’ / ‘valid’ value / anomalies
less significant / chance variations less significant;
Random sampling overcomes bias / independent of observer;
Ignore ‘fair’ / ‘accurate’ 2
(ii) Use of quadrat / nearest limpet to… ;
Grid / described – e.g. tape measures / walk to random coordinates;
Method of obtaining random coordinates – tables / calculator; 3
Sir George Monoux Sixth Form College 2
, (c) Any six from:
Yellow / green OR approx. 500-600mm
1. Penetrates water better;
2. Absorbed by phycoerythrin ;
3. Red seaweeds have phycoerythrin;
4. Red seaweeds photosynthesise in deep water;
Blue AND red OR approx. 460 and 670mm
5. Penetrate water poorly;
6. Absorbed by chlorophyll;
7. Green have only chlorophyll;
8. Green seaweeds can’t photosynthesise in deep water
9. Red seaweeds have less competition from green in deeper water /
converse in shallow water; 6 max
[15]
7. (a) (i) Time interval of 1 month / too long;
Large number of mice born / added to the population in this time /
die / lost from population;
OR
12 hours is too short a time;
For mice to mix in population / be recaptured;
OR
In non-seed years number of mice is small;
So may not catch any / any marked mice; 2
Reject answers about points not covered in the question.
(ii) Number of captures will vary with number of traps set /
number of traps varies;
Standardises results;
Allows results to be compared; 2 max
(b) (i) Less than 5% / 1 in 20 probability;
Of results being due to chance / luck;
Accept converse argument relating to biological significance. 2
(ii) More food;
Therefore mice able to produce more young / more mice survive; 2
(c) (i) Mass will vary with sex / one sex is lighter / heavier /
females may be pregnant; 1
(ii) Tooth wear linked to age / diet;
Confines sample to adult mice / mice eating same food;
Otherwise age / food contributes to variation / mass; 2 max
(d) (i) Smaller surface area to volume ratio;
So lose less heat;
OR
More (subcutaneous) fat;
Insulation;
OR
More respiration;
More heat produced; 2
Sir George Monoux Sixth Form College 3
, (ii) Variation in size is genetic;
Selection for / against one extreme (general point not related to
data) / for large mice / against small mice;
Only larger mice will (survive and) breed / pass on genes;
Leads to increase in mean mass;
In cold conditions (related to figure); 3 max
(e) (i) Grey by grey;
Produces some black; 2
(ii) Find frequency / percentage / proportion of black mice;
Square root;
Use Hardy-Weinberg equation; 2 max
[20]
8. (a) Insulates nerve fibre / axon / does not allow passage of ions / charge;
Ions only pass at non-myelinated points / nodes / action potential
only occurs at node;
Saltatory conduction (is faster) / description of ‘jumping’; 2 max
(b) Rise / fall in cholesterol concentration in cytoplasm / cell;
Reject references only to plasma concentrations;
Fall / rise in cholesterol receptors (in plasma membrane);
Leads to fall / rise in cholesterol / cholesterol returns to norm; 3
(c) (i) Mutation produces receptor with different shape / tertiary structure /
not specific to LDL;
So LDL will not bind to it and be absorbed / removed from the blood;
Do not penalise ‘active site’. 2
(ii) Endothelium / lining of artery torn / damaged;
Atheroma / plaque / underlying cells come into contact with blood;
Triggers blood clotting mechanism;
OR
Artery narrowed by plaque / atheroma;
May be blocked by clot from elsewhere; 2 max
(d) 2517;
Accept 2514 or 2511 if explanation refers to start / and stop codons. 1
(e) If recessive would inherit one allele from each parent; reject ‘gene’
Parents could be heterozygotes / carriers;
Parents / heterozygotes / carriers would not show the condition;
NB points 2 and 3 may appear in one linked sentence. 2
(f) 1003.;
Two marks for reason from below:
(As dominant,) both heterozygote and homozygote at risk;
(Heterozygotes 1 in 100 so) 1000 are heterozygous;
(Homozygotes 1 in 30000 so) .3 homozygous; 3 max
[15]
9. (a) (i) Same general structure as all amino acids; = 1 mark
Same general structure as all amino acids and answer making specific
reference
to amino/ NH2 group and carboxyl/ COOH group; 2
(ii) Not normally found in proteins/ polypeptides; 1
[Note: Alternative answers must fit with information provided
in passage]
Sir George Monoux Sixth Form College 4
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller ainhoa1. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £6.89. You're not tied to anything after your purchase.
