1. The uptake of water by a leafy shoot can be investigated using a potometer as shown in the diagram below.

(a) (i) What assumption is made when this apparatus is used to investigate the rate of transpiration? water loss / transpiration equals / is proportional to water uptake;

(1 mark)

(ii) State two precautions which must be taken setting up and using this apparatus. 1. cut stem under water;

assemble apparatus under water;

render apparatus water tight / air tight with vaseline / wax;

2. (run water through capillary to) eliminate air bubbles;

ensure leaves / eq. are dry;

control of variables / one variable specified; ref. to equilibration;

(2 marks)

(b) Using this apparatus, four experiments were carried out with the same shoot in the order given below.

A Still air, leaves untreated

B Moving air, leaves untreated

C Still air, lower surface of leaf covered with grease

D Moving air, lower surface of leaf covered with grease

Temperature and light intensity were kept constant during the investigation.

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The results are shown in the graph below.

B

A

DC

Dis

tanc

e m

oved

by

men

iscu

s / m

m

200

150

100

50

0

Time / min

0 5 10 15 20 25 30

The mean rate of water uptake during experiment A was 3.2 mm3 per minute.

The cross-sectional area of the bore of the capillary tube is 0.8 mm2. Calculate the mean rate of water uptake by the shoot during experiment B. Show your working.

(meniscus moves) 180 mm (in 30 minutes);

2.3120

1808.0

30

180

;

Answer 4.8 mm3 min–1;

(3 marks)

(c) (i) Describe and explain the effect of moving air on the rate of water uptake in experiment B. rate of water loss / transpiration / water uptake increased;

credit comparative reference to figures;

more water vapour blown away / eq.;

thus increasing / maintaining concentration gradient / eq;

causing faster / more diffusion;

(3 marks)

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(ii) Suggest an explanation for the different effects of moving air in experiments

B and D. moving air causes more water vapour to be lost from B than D / less from D than B / eq.;

more water (vapour) lost through stomata;

more stomata on lower surface of leaves;

grease prevents water loss through / blocks

these stomata / acts as a barrier;

(3 marks) [Total 12 marks]

2. Give an account of the flow of energy through of food web. 1. source of energy sunlight;

2. absorbed by photosynthetic pigments / named pigments;

3. converted to chemical / bond energy / used in formation ATP;

4. (energy) in the form of organic compounds / carbohydrates / named eg;

5. by photosynthesis in producers / green plants;

6. ref. to GPP + explanation / elaborations;

7. utilisation by producers / used in respiration by plants / eq;

8. any ref. to hear / energy losses from metabolism. respiration;

9. ref. to NPP + explanation / elaboration;

10. energy passed on / eq. by feeding relationships / eq; food chains / trophic levels

11. less energy at top of food chain / eq;

12. efficiency about 10%;

13. ref. to losses due to muscle contraction / locomotion / eq;

14. (energy) in the form of inedible / indigestible material / eq / not all eaten by next trophic level;

15. ref. to energy in forces / egested material;

16. utilisation of dead organisms by decomposers / eq;

17. energy in the form of excretory material;

18. named excretory material / urea;

19. losses to fossilisation;

20. ref. to chemoautotrophs;

[Total 10 marks]

3. An investigation was carried out into the effect of different concentrations of indoleacetic acid (IAA) on the growth of coleoptiles (shoots) from 5 day old barley seedlings.

The tips of 70 coleoptiles were cut off, and the remainder of each coleoptile was trimmed to a length of 10 mm. Ten of these trimmed coleoptiles were placed in each of six solutions of IAA, and then incubated in the dark at 20 oC for 72 hours. A further ten trimmed coleoptiles were incubated for the same length of time in distilled water.

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The coleoptiles were then measured, and the mean increases in their lengths were plotted against

the concentration of IAA used. The whole experiment was repeated at a temperature of 30 oC. The results are shown in the graph below.

25

20

15

10

5

00 0.001 0.01 0.1 1.0 10.0 100.0

Mea

n in

crea

se in

leng

th/m

m

Concentration of IAA / ppm(log scale)

Coleoptiles at 20ºC Coleoptiles at 30ºCKey

(a) Describe the effect of different concentrations of IAA on the growth of the coleoptiles. all concentrations of / IAA cause(s) an increase in length / eq;

concentrations 0.0 to 0.01 / from 0 to 0.001 cause small increase in length;

0.01. to 1.0 cause sleep increase in length;

1.0 to 100.0 cause lower increase in length/increase inhibited;

greatest increase at 1.0 / 1.0 is the optimum;

(3 marks)

(b) Suggest an explanation for the differences between the results obtained at 20 oC and at 30 oC.

IAA transported / eq. into coleoptiles more rapidly at 30oC / less rapidly at 20oc / increase in membrane permeability to IAA at 30oc;

increased enzyme / metabolic / eq. activity at 30oc / decreased at 20oC;

resulting in more / increased growth / elongation at 30oC / decreased at 20oC;

(2 marks)

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(c) (i) Suggest why the tips were removed from the coleoptiles.

ensures comparability of results / removes uncontrolled variable;

since IAA (produced) in tips;

different tips may produce different concentrations;

(2 marks)

(ii) Suggest why the investigation was carried out in the dark. light affects distribution of IAA / inactivates IAA / destroys IAA;

(1 mark)

(d) Explain one way in which auxins, such as IAA, may be used in horticulture and agriculture.

spray on broad leaved weeds / use as selective weedkiller; stimulates growth of weeds to exhaustion / eq;

dip cut stems / petiole into auxin / IAA powder. stimulates production / growth of (adventitious) roots;

spray on to unpollinated / unfertilised flowers of fruit trees; produces seedless fruits;

spray on to developing fruit / named e.g; to retard abscission / prevent fruit drop / eq;

add to nutrient agar solution; to stimulate clove formation / callus growth / micropropagation;

( = linked points)

(2 marks) [Total 10 marks]

4. (a) 1. Named species of coleoptile / seedling // standardisation of seedlings e.g. genetic uniformity ;

2. Grown in dark or even illumination / straight stemmed examples chosen ;

3. Fixed to microscope slide (allow from diagram) / method of preventing movement / tray / dish fixed in box ;

4. Damp cotton Wool /eq (to prevent drying) / in suitable medium ;

5. In darkened environment / dark box (control) and in box with slit /eq ;

6. Viewed under low power magnification ;

7. Aligned against suitable marker / eyepiece graticule / scale / ruler ;

8. Suitable means of unilateral illumination (allow box with slit /eq) ;

9. Movement / displacement measured on scale / angle of curvature measured on scale /eq ;

10. For fixed time / at suitable intervals (2 days maximum) ;

Maximum 5 if only a qualitative explanation Max 7

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(b) Difficult to set up unilateral light ;

Bending makes it difficult to keep coleoptile against scale / difficult to measure curved coleoptile / seedling stem ;

Difficult to set up fixed point for measurement ;

Straight seedlings / coleoptiles difficult to grow ; Max 2 [9]

5. (a) (i)

Insecticide dose /mg 0.15 0.25 0.35 0.45 0.55

Village with spraying % killed

18 28 38 40.8 (41)

52.8 (53)

Village with no spraying % killed

75.2 (75)

92 98 94 95.2 (95)

(Allow two significant figures)

Percentages with spraying correct ;

Percentages without spraying correct ;

Tabular format ;

Correct rows and columns units in heading ; 4

(ii) L Suitable axes labelled with units and correct scales ;

S Sprayed data correctly plotted ;

U Unsprayed data correctly plotted ;

K Line graph correctly keyed, accurately drawn and no extrapolation ; 4

(b) Sprayed village mosquitoes are more resistant // converse ;

% of sprayed village mosquitoes killed increases with increasing insecticide concentration ;

% of unsprayed village mosquitoes killed reaches maximum at (figure to match max from graph drawn 0.3 – 0.35) ; Max 2

[10]

6. (a) 1. Reference to need to know lifecycle of moth / time of infection of plants ;

2. Divide plantation into several areas / plots / use several plantations (allow use of (large) contained areas) ;

3. Control area (no pheromone / chemical or no traps if suitable) ;

4. Randomised selection of areas for tests ;

5. Same concentration of pheromone in each trap ;

6. Same area /eq sticky surface ;

7. Same suitable (measured) positions ;

8. Kept at same distance from trunk of tree / or other detail of standardising positions ; 9. Protect traps from rain ;

10. Add stated number of moths to contained areas ;

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11. Left for stated time / check traps at regular intervals ;

12. Count number of males trapped ;

13. Count damaged / undamaged leaves / count eggs or caterpillars ;

14. Replace traps at intervals ;

15. Record wind speed / direction ;

16. Record rainfall / temperature / control abiotic factor / variable in lab ;

17. Repeat procedure / replication in different areas ; Max 9

(b) Tabulation ;

Suitable columns / rows - units if appropriate ;

Calculation of mean (accept from table) ;

Bar chart different treatments ;

Number of trapped moths / % of leaves infected /eq on y axis

Possible scatter graphs e.g. number caught against height etc ;

Mann - Whitney U / t-test to compare any two treatments / compare with control / other test matched to their data ;

Suitable null hypothesis / reference. back to previously stated H0 ;

Use of 5% significance level ; Max 6

(c) Different weather conditions could affect the result / seasons reference ;

Cannot test all placements of traps ;

Moths could be killed by other factors / disease / predators ;

Moths may escape if stickiness wears off / traps kept up for too long / effect of pheromone decreases ;

Results due to wind direction / moths less likely to reach traps on windward side ;

Need to repeat in different years / different weather / seasons ;

Compare with chemical control method / other biological control ;

Test different concentrations /eq ;

Test long term effects to see if population reduced ;

Same technique on other insect pests ;

Investigate "stray" catches / incidental killing of other insects ;

Investigate different surface area of traps ; Max 6 [21]

7. No mark scheme available

8. No mark scheme available

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9. (a) 1. method of immobilisation described (alginate in solution of Ca2+ ions) ; 2. solution of lactase prepared ; 3. same concentration of lactase in both ; 4. equal volumes / mass of both used in tests ; 5. both tested without treatment (allow at room temperature) ; 6. method of heat treatment described e.g. water bath ; 7. good range of temperatures (minimum 5, from 30-100°C, excluding room temperature) ; 8. stated same time of treatment for each minimum 1 minute ; 9. samples cooled to standard temperature before activity tested ; 10. tested by adding to same / stated volume of lactose ; 11. same concentration of lactose each time ; 12. left / incubate for same time ; 13. reference to named method of testing for glucose produced, e.g. test strips (diabur) / quantitative Benedicts’ test ; 14. details of quantitative method, such as mass of precipitate with Benedicts’ / reference to colour scales for test strips ; 15. repeat whole procedure ; 9

(b) suitable table with correct rows and columns ; line graph (bar chart if only one temperature treatment in method) ; correctly orientated axes with labels and units ; suitable method of rate calculation described e.g. Concentration of glucose detected divided by incubation time ; 3

(c) difficult to standardise alginate bead sizes ; difficult to standardise concentration in beads and solution ; difficult to standardise time of heat treatment / higher temperatures take longer to heat up / take longer to cool to standard temperature ; difficult to determine end point ; alginate / calcium ions may affect rate of reaction ; investigate effect of different bead sizes ; investigate the effect on other enzymes ; investigate effect at different lactase concentrations ; use smaller increments of temperature (around point of denaturation) ; 6

[18]

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10. (a) 1. Same concentration of each amylase ;

2. Same volume of amylase used in each test ; 3. Standardised starch solution volume and concentration ; 4. Stated temperature for each test (15 – 50°C ); 5. Method of achieving standard temperature e.g. water bath ; 6. All solutions equilibrated at chosen temperature before mixing ; 7. Suitable range of pH values (min 5 values spread must be at least 5>9) ; 8. Use of buffer solutions ; 9. Method of measuring end point named e.g. disappearance of starch / quantitative Benedict’s test ; 10. Detail of measurement of end point e.g. drops tested with standard iodine every minute / excess Benedict’s and mass of precipitate / use of iodine with colorimeter ; 11. Repeat at each pH ; 12. Repeat whole procedure with alternative enzyme (watch for this in earlier description) ; 9

(b) Suitable table with correct rows and columns to match suggested method ; Bar chart / accept line graph where rates have been measured ; Correct orientation of the axes with labels and units ; Reference to rate calculation 1 / t etc. ; 3

(c) Limitations End point difficult to measure accurately ; Difficult to control concentrations of different enzymes / eq ; Difficult to carry out iodine tests at short intervals / time taken to carry out Benedict’s tests limits accuracy ; Difficult to adjust concentrations to get measurable timings / eq ; Different enzymes may have different optimum temperatures ;

Further work Use different / wider range of volumes / concentrations / pH values ; Compare results with / test other amylases ; Test to see if pH effect is permanent / reversible ; Research actual pH conditions for proposed use ; 6

[18]

11. (a) 1. Obtain yeast from same batch eq ; 2. Volume / mass yeast stated ; 3. Same / equal volume / concentration of redox / named indicator used ; 4. Same / equal volume / concentration of named substrate added ; 5. Same volume of sodium malonate added (if using different concentrations) ; 6. Same volume of distilled water added (if just testing with and without); 7. Stated temperature for test (maximum 60ºC, reject room temperature) OR use of water bath ; 8. Reference to equilibration of solutions separately ; 9. Time reference for equilibrium (1 minute or over); 10. Time to reach (standard) end point ; 11. Reference to appropriate colour change (of indicator) described / stated ; 12. Reference to standard end point by observation or by use of colorimeter / spectrophotometer ; 13. Repeat (3 times minimum) at same concentration ; 10

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Style Account is concise and well organised, there is good use of technical

vocabulary and almost no spelling errors. – 2 Marks

There is some lack of organisation, limited vocabulary and a number of spelling errors. – 1 Mark

The account lacks organisation, there is little or no technical vocabulary and many spelling errors. – 0 Marks 2

(b) Table of raw data with labelled rows and columns including units ; Reference to need to calculate means (accept from table) ; Suitable graphical format matched to suggested results table ; Correct axes with units; Reference to a named statistical test (accept from method plan) ; Reference to use of null hypothesis ; 4

(c) Limitations: Reference to difficulty in determining the end point accurately ; Reference to re-oxidation of indicators ; Inadequate mixing of solutions / uneven colour change ; Removal from water bath during colour determination ; Settling out of yeast culture samples ;

Further work:

Investigate: Different concentrations of sodium malonate ; The effects of different substrates (such as succinate) on the action of sodium malonate ; The effect of malonate on different strains of yeast or microbes ; The effect of malonate on anaerobic respiration ; The effect of other metabolic poisons ; 5

[21]

12. (a) 1. Stated number of subjects to be tested (minimum of 10) ;

2. Two named variables of subjects {controlled / selected} (age, gender, health, frequency of smoking) ;

3. Either test to be carried out on smokers or non-smokers OR before and after chewing gum ;

4. Type of gum chewed to be controlled e.g. brand ;

5. Gum chewed a stated length of time before test ;

6. Named test for reaction time e.g. falling ruler / computer programme / push button apparatus ;

For falling ruler test:

7. Ruler positioned accurately between thumb and first finger / eq ;

8. Any precaution to prevent anticipation e.g. use of oral command only looking away or with blindfold ;

9. Precisely what is to be measured e.g. top of fingers against ruler / eq ;

For computer programme / push button test:

7. Position of finger on {keyboard / mouse / button} standard at the start of the test ;

8. Description of stimulus for response ;

9. Precaution against anticipation e.g. randomised {stimulus / interval} ; 10. For either test separation of testing to minimise effects of {practise / learning} ;

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11. Repeat at least three times for each subject ; 8

Style Account is concise and well organised; there is good use of technical vocabulary and almost no spelling errors. – 2 marks

There is some lack of organisation, limited vocabulary and a number of spelling errors. – 1 mark

The account lacks organisation, there is little or no technical vocabulary and many spelling errors. – 0 marks 2

(b) Table of raw data with suitable accurately labelled rows and columns ;

Reference to calculation of means (accept from table) ;

Suitable graphical format matched to suggested data ;

Graphical presentation allows comparison ;

Named statistical test (accept from method plan) ;

Use of null hypothesis ; 6

(c) Limitations

Very difficult to eliminate effects of practise on reaction times ;

Reason for inaccuracy of ruler method e.g. initial position of finger difficult to standardise / visual method invites anticipation ;

Total response time involves several processes ;

Named human variable difficult to control (not illness) e.g mood, time of day etc. if not given as controlled factors ;

Further work

Use different techniques for measuring reaction time ;

Vary {concentrations of nicotine / time of chewing / amount of gum chewed / eq} ;

Investigate duration of nicotine effect ;

Investigate effects of nicotine on different subject groups, e.g. non-smokers with regular smokers / male with female ;

Investigate effects of chewing gum without nicotine ; 5 [21]

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13. (a)

Numberof elderseedlings

{Frequency / number} of elder seedlings in 0.25 m quadrats in fieldsgrazed by: (H = Horses and C = Cattle)

2

Tally chartSize class oftwo

Size class ofthree

Size class offour

Size class ofsix

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

H H

0

0

0

00

2

2

4

10

4

4

6

5

3

2

1

3

5

5

1

3

3

1

2

2

4

4

1

1

2

H H HC C

1

2

2

23

4

5

10

4

1

8

3

2

0

3

5

5

3

1

1

0

5

3

2

2

1

1

1

0

0

C C C

Tallies recorded;

Correct rows and columns with labels and units (accept per quad); Suitable size classes; Correct frequencies of size classes for horses and cattle; 4

(b) F Format, bar chart format with correct axes orientation and labels;

S Scale, use more than ½ of the paper and correct scale;

P Plotting all points correctly; 3

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(c) There is no difference in the {number / frequency} of elder seedlings

between the two grazed areas; 1

(d) Calculated value of t is greater than the tabulated value; There is a significant difference in the {number / frequency} of elder seedlings in the two areas; At the 5% confidence level / greater than 2.02; 3

[11]

14. (a)

Width of lichen on

Birch / mm Oak / mm

8 6

16 9

18 12

21 13

22 14

24 15 Median

28 16

33 19

35 20

55 33

60 45

Median width / mm

24 15

Median Median width / mm

Width of lichen on Birch / mm

8 16 18 21 22 24 28 33 35 55 60 24

Width of lichen on Oak / mm

6 9 12 13 14 15 16 19 20 33 45 15

[Shaded rows/columns are alternative to each other]

Neat table correctly formatted including medians (if medians have been identified);

Correctly labelled rows or columns with units;

Widths ranked;

Both medians correct. 4

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(b) A Graph correctly orientated with labelled axes;

F Bar chart for {medians - 24 and 15) / means - 29 and 18} OR histogram for sizes classes (table below);

Size class / mm Birch Oak

0 – 19 3 8

20 – 39 6 2

40 – 59 1 1

60 – 79 1 0

[format mark not awarded for raw data plots]

P Data plotted correctly 3

(c) There is no significant difference between the width of lichen on birch and oak 1

(d) There is a significant difference between the (median) width of lichen on birch and oak / reject the null hypothesis;

At the 5% value; [not just P = 0.05]

Since the {smallest U / U2} value is less than (the critical value) 30; 3 [11]

15. (a) 1. Sites selected to minimise at least 2 named edaphic variables e.g. type of soil / pH / mineral content;

2. Sites selected to minimise at least 2 named other abiotic variables e.g. light / temperature / rainfall;

3. Assessment of area of {grass / dung} in each site before investigation;

4. Same number of cattle to graze each site / same mass of dung added to each site;

5. All wild type beetles {removed / destroyed} in {one site / whole area};

6. ‘Superpat’ and wild type beetles standardised;

7. Reference to attempt to release similar numbers of ‘Superpat’ as population of ‘wild type’ / equal numbers released on each site;

8. Any suitable precaution to prevent {migration / escape} of ‘Superpat’ beetles;

9. Sites left for suitable time (minimum 1 week);

10. Suitable method of randomising sampling;

11. Use of quadrat of stated size (minimum 10 samples);

12. Details of exactly what is measured / percentage cover grass or dung / count squares in gridded quadrat / weigh dung; 8

SPG Account is concise and well-organised, there is good use of technical vocabulary and almost no spelling errors – 2 marks

There is some lack of organisation, limited vocabulary and a number of spelling errors – 1mark

The account lacks organisation, there is little or no technical vocabulary and many spelling errors – 0 marks 2

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(b) Table of raw data with suitable accurately labelled rows and columns with units;

Reference to calculation of means; [accept from table]

Suitable graphical format which matches data and method including correctly labelled axes;

Graphical presentation allows comparison of two sites;

Reference to suitable type of statistical test [for significant difference] between means; [accept from method plan]

Use of stated null hypothesis; [accept from method plan] 6

(c) Limitations: [Sub-maximum 4 marks]

Difficult to match conditions at both sites;

Difficult to control level of dung at each site;

Difficult to achieve random distribution of ‘Superpat’ beetles;

Despite precautions beetles may {migrate / die};

Possible delay in build up of full population of ‘Superpat’ beetles;

Dung may be removed by other organisms;

Further work:

Study effect at different seasons;

Measure actual rates of {feeding / dung removal} (by direct observations of individuals);

Investigate removal of dung with different types of cattle; 5 [21]

16. (a) (i) 1. Bacteria {remain attached to filter paper / not dispersed in solution / more stable};

2. So that luminescence is easier to see / eq;

3. Can be removed easily;

(ii) 1. (Changes in temperature) affect enzyme (activity);

2. Affect {metabolism / respiration / bioluminescence / eq};

3. May affect uptake of {ions / metals / eq}; 4

(b) As concentration increased, light emitted decreased / converse;

0.05 mg dm-3 had no effect (within 5 hours) / 10.0 mg dm-3 inhibited light emission within 30 mins / equivalent statement about other concentration; 2

(c) Mercury (chloride);

More {rapid effect / effective at lower concentrations} (than other metals) / eq; 2

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(d) 1. Set up with filter paper disc plus bacteria in water sample;

2. Reference to use of a control;

3. Keep (both) {at the same temperature / in dark};

4. Record duration of light emission;

5. Expect shorter duration (than control) if water had been polluted / eq; 3 [11]

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