Download 1. (a) - The West Bridgford School

1.
(a)
Release ammonia / ammonium / ammonification;
BY
Decomposers / putrefying / saprotrophic / ammonifying bacteria;
ammonia → nitrite → nitrate / nitrification;
BY
(b)
nitrifying bacteria / named bacteria;
max. 3
(Interspecific) competition;
for nitrates / nitrites / ammonia / ammonium compounds;
2
[5]
[Process is stand alone - bacteria only credited if in correct context.]
2.
(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;
diversity is reduced;
(d)
max. 3
{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]
3.
(a)
(i)
(ii)
(b)
(c)
pyramid correctly drawn and labelled;
ignore organic matter
1
energy lost/not transferred between trophic levels;
in respiration /as heat / in excretory products / movement;
ignore in urea / in faeces. ‘Growth’ cancels 2nd marking point only
2
(i)
decomposers convert (nitrogen in organic compounds) into
ammonia/ammonium;
suitable example of “organic nitrogen” - protein/urea/amino acid etc.
(e.g. linked to process);
nitrifying bacteria / correctly named convert ammonium to nitrate;
via nitrite;
3 max
(ii)
convert nitrogen (gas) into ammonium / ammonia / amino acids;
add usable/available nitrogen to an ecosystem / eq.;
(i)
2
1. numbers of dispersed bacteria increase as they feed on organic matter;
West Bridgford School
1
2. numbers of free-swimming protoctistans increase because number
of bacteria increase;
3. dispersed bacteria decease as amount of dispersed organic matter
decreases / due to lack of food / as organic matter is converted to flocs;
4. decrease as are preyed on by free-swimming protoctistans;
5. decrease in free-swimming protoctistans due to lack of dispersed
bacteria;
3 max
(ii)
1. (in a succession) organisms (enter an area and) change the
environment/conditions;
2. creating new niches / habitats;
3. allows different species / different types of organisms to enter /
be successful;
4. dispersed bacteria change dispersed organic matter to floes;
5. presence of flocs allows crawling protoctistans to enter / to increase /
to be successful;
4 max
[15]
4.
(a)
(b)
Grid;
Selection of coordinates using
random number tables/ numbers from a hat;
Dead plant material /humus is converted to nitrate by soil bacteria;
(one mark for principle)
Plant material decomposed by saprophytes/ saprobionts;
Organic molecules containing nitrogen / protein converted to ammonia;
Involving ammonifying bacteria;
Ammonia to nitrite; nitrite to nitrate;
Involving nitrifying bacteria;
2
4 max
[6]
5.
(a)
(i)
Correct answer (0.5%) awarded two marks;;
answer involving decimal point in wrong place but derived
correctly / correct working only awarded 1 mark
(ii)
Some fails to encounter chloroplasts/chlorophyll in producers
(e.g. some absorbed by water);
reflection;
inappropriate wavelength;
West Bridgford School
2
max. 2
2
(b)
(c)
(d)
Only a certain amount of light energy available / not enough energy left;
respiratory loss between each trophic level / loss in faeces;
Incorporated in tissues of decomposers;
passed on to other organisms in decomposer food chain;
lost in respiration by decomposers;
(i)
(ii)
(e)
(f)
2
max. 2
Excites/raises energy level of electrons;
which pass to carriers/leave chlorophyll;
2
Fall in production of triose phosphate/no more triose phosphate produced;
triose phosphate production requires ATP/reduced NADP;
produced during passage of electrons along electron transport chain;
3
Energy is available more rapidly because released in single reaction /
does not go through as many processes;
ATP releases its energy in small/manageable quantities;
(i)
(ii)
2
Activity / needs of cell linked to level of ATP / ADP ;
link made between high level of one and low level of the other;
level of ADP linked to electron transport and ATP production;
3
Energy released as heat;
because not used to produce ATP;
2
[20]
6.
(a)
(i)
Stage
A
B
(b)
Name of stage
Glycolysis
Krebs cycle / citric acid cycle /
TCA cycle
Location in cell
Cytoplasm
Mitochondrion (ignore
named part)
1 mark per row;;
2
(ii)
3;
1
(iii)
To oxygen;
Produce water;
2
(i)
4;
1
(ii)
34;
1
West Bridgford School
3
(c)
(i)
×100;
Correct calculation - [answer from (b)(i) + (ii)] x 31]
2880
Answer correct from calculation;
OR
Correct answer from (b) / 41% (no working) = 2 marks;;
2
(ii)
Lost as heat;
1
(iii)
Energy available (more) rapidly / released in a single reaction;
Energy released in small quantities / manageable quantities;
2
(iv)
Any three from:
Active transport;
Phagocytosis;
Synthesis of glycogen;
Protein / enzyme;
DNA / RNA;
Lipid / cholesterol;
Urea in glycolysis;
Bile production;
Cell division;
Any other valid suggestion;
3 max
[15]
7.
(a)
(b)
(c)
(i)
Oxidative phosphorylation/electron transport chain/ETC;
1
(ii)
Link reaction and Krebs cycle (or clear descriptions);
1
Respiring anaerobically;
Less efficient/requires more glucose for same amount of ATP;
2
Energy from chemical reaction/oxidation/not from light;
1
[5]
8.
(a)
1 and 3;
1
(b)
Some energy lost as heat;
1
(c)
(i)
Arrow indicates between Glucose to Triose phosphate;
(ii)
Arrow indicates between Triose phosphate to Pyruvate;
[Note: Extra arrow cancels]
[Reject: Ambiguous labels /arrows]
West Bridgford School
2
4
(d)
4;
(e)
(i)
Grana/ thylakolds/ internal membranes;
1
(ii)
Reduces/ reducing power/ source of hydrogen/ electrons;
Glycerate-3-phosphate to Triose phosphate/ GP to TP;
[Ignore: Reference to molecules]
2
(i)
To show chloroplasts responsible for change;
1
(ii)
Photolysis/ light splits water molecule/ excitation of chlorophyll:
Electrons released;
Electrons reduce DCPIP/ DCPIP becomes colourless;
So can only see (green) colour of chloroplasts/ chlorophyll;
max 3
Mitochondria are sites of (aerobic) respiration/ active in dark;
Reactions also release hydrogen ions/ electrons;
(Tube B) would also become green/ reduce DCPIP (if responsible);
[Reject: Colourless] [Reject.- Converse argument]
Tube B shows light is necessary for colour change;
Mitochondria do not have pigment to absorb light/ chlorophyll;
max 2
(f)
(g)
(i)
OR
(ii)
1
Only one set of results/ not repeated;
[Reject: Need more results]
1
[15]
9.
(a)
(i)
(ii)
(b)
(c)
CO2 combines with RuBP/with ribulose bisphosphate;
(Product) splits in two/production of two molecules of GP/use
of RubisCo;
2
Amount formed = amount broken down/used/reference to Equilibrium;
1
Any three from:
No ATP made (in dark);
No reduced NADP / NADPH (in dark); [Note: NOT “NADH”]
GP not converted (in dark);
TP not formed (in dark);
(i)
(ii)
max 3
During day/light photosynthesis occurs;
(Photosynthesis) uses/takes in CO2;
[Accept: converse explanation during darkness]
2
Higher;
Less light/cooler/fewer leaves/CO2 formed from soil organisms/decay
in soil/respiration in soil;
2
West Bridgford School
5
(d)
(e)
Wind mixes air (with surrounding air)/removes CO2/supplies CO2;
Introduces another variable/makes data unreliable/takes account of wind;
2
Any three from:
Detritivores/worms/woodlice/other e.g./decomposers/microorganisms/
bacteria/fungi;
Digestion/hydrolysis (of organic matter/of leaves)/decay/decomposition/
rotting;
Respiration;
Releases CO2;
max3
[15]
10.
(a)
(b)
(c)
–
Nitrate/NO 3 /nitrite/ NO 2 ;
1
(ii)
Nitrification;
1
(iii)
Denitrification;
1
(i)
(Increase) fertiliser increases yield up to 150 kg hectare–1;
1
(ii)
(Excess) runs off/leaching/washed out;
eutrophication;
no extra yield;
cost (only once)/economic waste;
kills crops; due to osmotic effects/pH imbalance;
max. 4
(i)
Continuous;
(ii)
A has a smaller range of heights;
A is shorter/explained;
A is skewed;
(allow converse)
max. 2
Mutation;
selection;
genetic modification;
max. 2
Less stem damage in wind;
more energy used for seed formation/greater yield of seed/grain;
easier to harvest;
max. 2
(iii)
(iv)
(d)
–
(i)
1
(i)
AB and ab; → spaced or ringed
1
(ii)
Genotype: AaBb;
Phenotype: 70cm
2
[18]
West Bridgford School
6
11.
(a)
(b)
Greater effect on straw / no significant difference/
2% more on straw;
Grain yield increases 30.1% / 30%;
Straw yield increases 32.24% / 32%;
(i)
3
324 / 622;
= 0.524;
OR
(ii)
(c)
622 / 324;
= 1.92;
One mark for working, one mark for correct answer
2
Grain is useful but straw is not / less useful;
1
2 max
Competition for named factor;
Early
More available for
crop / crop
establishes / later in
season, outcompete
weeds;
Later
Less available for
crop / crop doesn’t
establish well / when
weeds removed
cannot make up lost
production;
[8]
12.
Quality of language
The answer to this question requires continuous prose. Quality of language should be
considered in crediting points in the mark scheme. In order to gain credit, answers must be
expressed logically in clear scientific terms.
(a)
Any three from:
Loss of habitat / nest sites / shelter / niche; ignore ‘homes’
Loss of food;
Exposure of soil leads to erosion / leaching of ions;
Change in (micro)climate / levels of light / temperature / humidity;
Animals move away / higher death rate / extinction;
West Bridgford School
3 max
7
(b)
Any three from:
Absorb carbon dioxide; (extra carbon-sources CANCEL)
In photosynthesis;
Carbon (dioxide) is used in forming permanent plant tissues /
biomass / plant structures;
Carbon is incorporated in organic molecules / named e.g.;
(c)
(i)
Any four from:
Less oxygen can enter the soil (from the air);
For saprobionts / soil microorganisms / bacteria / fungi /
decomposers / correctly named soil organisms;
For use in aerobic respiration;
Less breakdown of organic matter / humus / dead plants /
dead animals / other e.g.;
Less carbon dioxide released / formed;
(ii)
3 max
4 max
Any five from:
Oxygen enters the soil / use of oxygen;
Nitrifying bacteria are aerobic;
Ammonia / ammonium ions → nitrite;
Nitrite → nitrate;
(Ammonia → nitrate = 1 mark)
(If formulae used, worth 1 mark only if correct)
Nitrate is absorbed / used by plants;
To make named organic-N – e.g. protein / amino acids / DNA /
ATP / NAD(P) / chlorophyll;
Increased yield / growth;
5 max
[15]
13.
(a)
(b)
carbon dioxide taken in as a result of photosynthesis / more
photosynthesis than respiration;
idea that carbon is fixed/incorporated into compounds in the trees;
(reject sugar)
2
3800 =20.65 – 21.1 (allow 20.7 to 20.11 but disqualify 20.6)
180 – 184
(correct method of calculation = 1 mark)
(correct answer = 2 marks)
2
West Bridgford School
8
(c)
(d)
extracellular digestion;
by secretion of enzymes;
absorption of digested/soluble products;
synthesis of structural compounds/named compound;
respiration provide energy for growth;
4 max
higher temperatures, increasing enzyme action/decay / microorganism activity;
1
[9]
14.
(a)
OR
(b)
(c)
(d)
‘Slash’ / cutting down trees reduces photosynthesis;
Reduces removal of carbon dioxide from atmosphere;
‘Burn’ combustion releases carbon dioxide;
‘Slash’ cutting down trees removes respiring organisms;
Reduces removal of carbon dioxide into atmosphere;
‘Burn’ / combustion releases carbon dioxide;
max 2
(Before clearing) soil exists / already produced;
(After clearing) recolonisation by new plants / seeds;
(Brings about) change in environment / soil;
(Allows) succession;
(Leading to) climax (community);
max 3
1 Ammonium compounds from proteins / amino acids urea / N-containing;
2 Converted into nitrite;
3 Into nitrate; [Reject: Incorrect sequence once]
4 By nitrifying bacteria / correctly named;
5 Nitrogen-fixing bacteria;
6 Fix nitrogen from atmosphere / air;
7 Nitrate taken up by plants;
8 Nitrogen needed for protein synthesis / plant growth;
max 6
Trees available as a sustainable resource;
Maintain habitats / niches / shelter;
Maintain diversity / avoid loss of species / protect endangered species.
Maintain stability (of ecosystem);
Maintain food chains / webs / supply of food;
Reduced loss of soil / erosion;
Reduced flooding;
Act as carbon sink / maintainO2and C02 balance reduce greenhouse effect
Reduce global warming;
Source of medicines;
[Ignore: eutrophication]
max 4
[15]
West Bridgford School
9
15.
(a)
(b)
Shells;
Spray/flooding by seawater;
Weathering of underlying rock;
Nitrogen fixation;
Excretory products;
max 2
One mark for correct numbers = 4, 1, 1/2;
(i)
The last stage in succession, therefore furthest from sea
has greatest diversity/number of species of plants;
greatest amount of organic matter;
(ii)
Little humus/organic matter to hold/retain moisture/
More sand promoting drainage;
(iii)
Pioneer species/colonisers are often wind-dispersed/need large
numbers of small seeds in order for some to land on bare sand;
4
[6]
16.
(a)
(i)
Substitutions;
only affect specific codons/not all codons affected;
therefore only a few amino acids affected;
or
(ii)
(b)
(c)
Degenerate code;
some amino acids have more than one codon;
may mean mutations code for same amino acids/
only a few amino acids affected;
max 2
Frame shift/sequence of bases/codons/triplets changed from that
point on;
sequence of amino acids changed;
protein will have different tertiary structure;
active site affected;
max 3
Genetic probe is single stranded DNA;
with complementary base sequence/is a complementary strand;
chains of DNA separated (by heating);
probe attached by hydrogen bonding;
probe labelled/radioactive/fluorescent so can be detected;
(If probe described as RNA, then max =2)
max 3
(i)
IA and IO;
1
(ii)
Blood group B;
1
(iii)
Probability of child being boy indicated as 0.5 and probability
of child being blood group A indicated as 0.5;
0.25 or other correct expression;
2
West Bridgford School
10
(d)
(i)
Person with blood group O has no antigens/has unchanged antigens;
cannot provoke a response by antibodies/cannot cause a
reaction/agglutination/with anti A or anti B;
(Not just ‘immune response’)
2
Person with blood group O has both anti A and anti B/
has both antibodies;
will react with/agglutinate any red cells with any antigens/
A/B / AB / have antigens which will react;
(do not allow ‘attack’)
2
(i)
0.27;
1
(ii)
Blood groups B and O have anti-A antibodies;
these match/fit A antigen;
which has similar shape to surface proteins on smallpox virus;
recognition as non-self
may ∴ also agglutinate/react with/fit/match smallpox antigen;
(ii)
(e)
max 3
[20]
17.
(a)
EITHER:
q2 = 0.36 / q = 0.6/0.61;
p = (1 – 0.6) = 0.4/0.39;
48/47.9 = 3 marks
OR (If no correct calculations)
(b)
Allow 1 mark for use of H – W equation:
p + q = 1 /p2+2pq + q2 = 1
max. 3
No selection;
random mating/no sexual selection;
large population/gene pool;
no emigration/immigration/no migration/isolated population;
no mutation;
equally viable gametes/all equally fertile;
generations do not overlap;
max. 2
[5]
18.
(a)
(b)
1ndividual 7 Ff,
individual 11
Working shows probability next child will have cystic fibrosis =
and M/F = 50% / 0.5/½;
1
answer given as
/ 0.125 / 1 (chance) in 8 / 12.5%;
8
West Bridgford School
1
1
FF and Ff,
1
4
or 0.25
2
11
(c)
(d)
(i)
Able to insert nucleic acid/DNA into cells/viruses enter/invade cells;
(ii)
Difficult to get DNA/modified gene (or equivalent) into sufficient
cells/DNA may be inserted but not expressed;
correct reference to use of method on somatic/body cells not at
gamete/zygote stage;
DNA only inserted into differentiated cells;
treatment must be repeated;
correct reference to effects of cystic fibrosis on other organs;
Calculation attempts to find square root of 2 500 or 1/2500 or 0.0004;
0.02;
A 1/50 or 1 in 50 or 2%
1
max. 1
2
[8]
19.
(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;
Reject answers about points not covered in the question.
(ii)
(b)
(i)
(ii)
(c)
(i)
(ii)
Number of captures will vary with number of traps set /
number of traps varies;
Standardises results;
Allows results to be compared;
2
2 max
Less than 5% / 1 in 20 probability;
Of results being due to chance / luck;
Accept converse argument relating to biological significance.
2
More food;
Therefore mice able to produce more young / more mice survive;
2
Mass will vary with sex / one sex is lighter / heavier /
females may be pregnant;
1
Tooth wear linked to age / diet;
Confines sample to adult mice / mice eating same food;
Otherwise age / food contributes to variation / mass;
West Bridgford School
2 max
12
(d)
(i)
Smaller surface area to volume ratio;
So lose less heat;
OR
More (subcutaneous) fat;
Insulation;
OR
More respiration;
More heat produced;
(ii)
(e)
(i)
(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);
Grey by grey;
Produces some black;
Find frequency / percentage / proportion of black mice;
Square root;
Use Hardy-Weinberg equation;
2
3 max
2
2 max
[20]
West Bridgford School
13