edexcel biology a2 2007 jan all

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Mark Scheme January 2007

GCE

InternationalGCE Biology (8040/9040)GCE Biology (Human) (8042/9042)

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January 2007

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Contents

MARK SCHEMES

pg

Unit 3 6103/02 W1 Written Alternative 1

Unit 5B 6105/01 Genetics, evolution and biodiversity 5

Unit 6 6106/02 W2

6106/03

Written Alternative

Synoptic paper

14

18

Please note that this document is an International Supplement to the GCE Biology /Biology (Human) Mark Schemes (8040/8042/9040/9042) and provides Mark Schemesfor Units 5 and 6, which were only available to International centres.



GENERAL INTRODUCTION

Mark schemes are prepared by the Principal Examiners and revised, together with therelevant questions, by a panel of senior examiners and subject teachers. Theschemes are further amended at the Standardisation meetings attended by allexaminers. The Standardisation meeting ensures as far as possible that the markscheme covers the candidates' actual responses to questions and that every examinerunderstands and applies it in the same way.

The schemes in this document are the final mark schemes used by the examiners inthis examination and include the amendments made at the meeting. They do notinclude any details of the discussions that took place in the meeting, nor do theyinclude all of the possible alternative answers or equivalent statements that wereconsidered to be worthy of credit.

It is emphasised that these mark schemes are working documents that apply to these

papers in this examination. Every effort is made to ensure a consistent approach tomarking from one examination to another but each marking point has to be judged inthe context of the candidates' responses and in relation to the other questions in thepaper. It should not be assumed that future mark schemes will adopt exactly thesame marking points as this one.

Edexcel cannot under any circumstances discuss or comment informally on themarking of individual scripts. Any enquiries about the marks awarded toindividual candidates can be dealt with only through the official Enquiry aboutResults procedure.



January 2007 6103-02 Unit 3 Mark Scheme

6103-02 January 20071

Unit 3 W2 (6103-02)

Question 1 Maximum Marks

Water loss / m gh -1(Exoskeleton)

temperature/ 0C

Expt 1 Expt 2 Expt 3 mean

25.0 4 5 4 4.33/4.3

26.0 5 5 5 5.00/5.0

28.0 8 7 10 8.33/8.3

29.0 9 10 10 9.67/9.7

29.5 25 23 28 25.33/25.3

30.0 38 35 37 36.67/36.7

32.0 46 43 42 43.67/43.7

36.0 68 70 67 68.33/68.3

(a) suitable table format ;

rows and columns with correct headings and units ; [shaded areasoptional]

all means correct ; ; [1 error=1 mark, 2 errors=0 marks]4 marks

(b) F line graph format ;

A axes correct - scale, orientation and labelled with units ;

P all points plotted correctly ;

L suitable line – point to point or good curve ;4 marks

(c) rate of water loss increases as temperature increases ;

there is a large increase at 29.5 ° C / between 29-30 °C ;

2 marks

(d) variability in readings is much greater at 29.5 °C (than 29 °C or 30 °C) ;

readings at this temperature are less reliable / changing rapidly ;

2 marks




6103-02 January 20072

Question 1 continued Maximum Marks

(e) exoskeleton /eq must be changing in some way at 29.5 °C (to allow morewater through) ;

at temperatures above 29 °C /eq cockroaches may dehydrate/need tofind water/remain in damp places / eq ;

2 marks

Total 14 marks




6103-02 January 20073

Question 2 Maximum marks

(a) 1 standardise source of inhibitor [specific part of flesh, cork boredextracts] from GalaOR standardise source of Bramley tissue / same ripeness or age ref. ;

2 same/stated mass of apple (tissue) from Gala ;

3 {grind / macerate / homogenise} Gala apple material (for same time) ;

4 filter extract(s) / centrifuge (to obtain enzyme) ;

5 boil (one half) of Gala extract / use of control without Gala extract ;

6 use {discs of same surface area from Bramley / same mass / volume of homogenate} ;

7 attempt to standardise {an end point (by the use of colour chart /photographs / eq) / a method of determining surface area of browning(since non uniform)} / use of colorimeter in correct context ;

8 standardise experimental temperature conditions by use of incubator /eq ;

9 add stated volume of Gala extract to Bramley apple ;

10 time to reach (standard) brown colour OR surface area of browningafter specified time ;

11 repeat minimum of three times ;

12 ref. to minimising effects of oxidation in preparation ;

9 marks

(b) suitable table with units and correct rows and columns to include raw data tomatch suggested method ;

mean reaction time ;

bar chart and comparative / correct format for method described ;

correct orientation of axes with labels and units ;

3 marks




6103-02 January 20074

Question 2 Continued Maximum marks

(c) Limitations:

difficult to standardise /eq end point ;

difficult to keep apple browning the same (before addition of inhibitor extracts) ;

other chemicals may affect (colour change in) apples (chemicals that are alsoheat labile) ;

immersion in / covering by solution may prevent / alter action of inhibitor onapple tissue ;

uneven distribution of enzyme / inhibitor in apple tissue ;

Further work:

Investigate:

inhibitor activity (from Gala apples) on other varieties of apples ;

presence of inhibitor in other varieties of apples ;

use of inhibitor enzyme in apple preservation / apples in fruit salads eq ;

effect of inhibitor enzyme on other named plant organ (e.g. potatoes) ;

compare effect of other named browning inhibitors ;

6 marks

Total 18 marks



January 2007 6105 Unit 5B Mark Scheme

6105 January 20075

Unit 5B (6105)


1 auxin / named example of an auxin such as IAA ;

2 extension of {internode / stem} / cell elongation / breaking dormancy in

{seeds /buds} / development of side shoots / causing leaf growth / reversal of

dwarfism / bolting;

3 cell division / cell differentiation / cell expansion in leaves / combat aging in

leaves /eq ;

4 abscisic acid / ABA;

5 ripening fruit / inducing flowering ;

Total 5 marks




6105 January 20076


(a) (i) prophase 1 ;1 mark

(ii) A = chromatid B = centromere C = chiasma / chiasmata ;;

[3 correct = 2 marks, 2 correct = 1 mark]2 marks

(b) (i) (all) BbRr with black, rough fur ;

1 mark

(ii) 9 3 3 1 ;1 mark

(iii) 1 ref. to expected numbers would be 27 black, rough : 9 black,smooth : 9 white, rough : 3 white, smooth ;

2 the actual results differ from {expected ones / 9:3:3:1 ratio} ;

3 genes for fur colour and texture are {on same chromosome /linked} ;

4 tend to be inherited together ;

5 only separated if {chiasma(ta) forms between them / crossingover takes place} ;

6 ref. to recombinants ;

7 recombinants are black with smooth fur and/or white withrough fur ;

4 marks

Total 9 marks




6105 January 20077


(a) (i) labelling: 3 correct = 2 ;;

2 correct = 1

1 correct = 0

drawing: plan with no cells;

vein / midrib / upper epidermis shown in whole leaf;

all features shown in whole leaf;

5 marks

(a) (ii) palisade – {packed with chloroplasts /chloroplasts can move in thecytoplasm to intercept light / lies under epidermis} to maximise theamount of light trapped ;

spongy - some chloroplasts so can absorb light / ref. to air spaces toassist {diffusion of gases / gas exchange} ;

lower epidermis - presence of stomata to allow {the entry of carbon

dioxide / exit of oxygen} ;

3 marks

(b) {large surface area / eq} to {maximise amount of light trapped / eq} ;

more {chlorophyll/chloroplasts} to {maximise photosynthesis / trap as muchlight as possible} ;

{more layers of palisade mesophyll cells / longer palisade cells / eq} to trapmore light ;

any other valid comment ;

2 marks

Total 10 marks




6105 January 20078


(a) (i) A = protein

B = phospholipid (bilayer);

1 mark

(ii) C = glycoprotein / glycocalyx ;

Role: recognition / antigen / receptor site / binds cells together /eq ;

2 marks

(b) (i) 1 active transport and diffusion both involved ;

2 ref. to {some / little / low rate of} diffusion / mainly activetransport ;

3 hardly any ions transported without ATP, with ATP rate of transport is higher ;

4 diffusion only when no ATP present ;

5 active transport requires energy / ATP {supplies energy / isenergy source / eq} ;

6 allows ions to {accumulate / build up / move againstconcentration gradient} ;

4 marks




6105 January 20079


(ii) 1 sodium ions {actively transported / pumped} out of ascendinglimb ;

2 together with chloride ions ;

3 into {medulla / medullary tissue} ;

4 ions accumulate in {medulla / medullary tissue} ;

5 ref. to lower water potential in {medulla / medullary tissue}/ eq ;

6 water moves out of {descending limb / collecting ducts} by{osmosis / diffusion} ;

7 ref. to {increases concentration of urine / countercurrentmultiplier} ;

4 marks

Total 11 marks




6105 January 200710


(a) (i) (overall trend) as conc. of caffeine decreases, heart rate decreases

OR

converse as caffeine conc. increases, heart rate increases ;

largest decrease between 1000 and 100 ppm / allow converse ;

very low concentrations (0.0001 and lower) have no effect on heart

rate ;

increase linear between 0.0001 and 1.0, then increase greater;

3 marks

(ii) ((5.6 – 3.7) ÷ 3.7) x 100 ;

51.4 / 51.35 ;

2 marks

(b) to observe the effect of no caffeine on the heart rate / to obtain a base

reading ;

1 mark

(c) 1 to eliminate a source of error ;

2 Daphnia are {ectothermic / eq} animals ;

3 {metabolic rate / eq} depends on temperature ;

4 if temperature changes, heart rate changes ;

5 this could have masked the effect of caffeine on heart rate / ref. to

temperature affects concentration of oxygen in water ;

3 marks

(d) 1 nicotine is {a mimic of / chemically similar to} acetyl choline ;

2 nicotine binds to the receptors on the post synaptic membrane ;

3 results in {action potentials being generated / depolarisation} ;

4 then blocks the synapse / not broken down ;

2 marks

Total 11 marks




6105 January 200711


(a) maltose ;ref. to hydrolysis ;of glycosidic bond ;by maltase ;

[max = 2 if maltose not identified]

3 marks

(b) 1 villi increase surface area ;

2 microvilli increase surface area of (epithelial) cell (surface)membrane;

3 ref. to capillary networks in villi (remove glucose to) maintain{concentration / diffusion} gradient ;

4 {thin / single cell} epithelium reduces distance between {lumen / eq}and the blood ;

5 ref. to {carrier proteins / sodium ion mechanism / co-transport of glucose} in cell (surface) membrane of epithelium ;

3 marks

(c) (i) 1 ref. to negative feedback ;

2 increase in blood glucose detected by β-cells (in pancreas) ;

3 insulin released ;

4 from {β-cells / Islets of Langerhans} (in pancreas) ;

5 glucose to glycogen and fat / ref. to glycogenesis ;

6 in liver ;

7 increase permeability of cell membrane to glucose ;

8 ref. to conversion of glucose to fatty acids / fats ;

9 glucose levels turn to {normal / set point} ;

6 marks

Total 12 marks




6105 January 200712


(a) succession ;

1 mark

(b) 1 increased number of species as succession progresses / number of

species increases from grassland to woodland ;

2 any suitable manipulation of data ;

3 grassland is open habitat but trees provide more cover ;

4 birds easily spotted by predators in grass / converse for trees and

shrubs ;

5 trees provide {roosting / nesting} sites;

6 mixed woodland provides greater variety of food to support more

species ;

7 trees provide more niches for species than smaller shrubs ;

5 marks

(c) 1 pine trees have less food available for birds / eq ;

2 needles on the woodland floor do not support as many invertebrates /eq (which birds eat) ;

3 reduction in the variety of {microhabitats / niches} ;

4 idea that mixed woodland {has many layers / is more varied} that

shelters birds / provide nesting sites;

2 marks




6105 January 200713


(d) 1 deforestation / eq ;

2 leaves soil exposed to erosion / loss of habitats / change in

biodiversity ;

3 acid rain / eq;

4 damages leaves / needles of trees / eq;

5 global warming / increase in greenhouse gases / eq ;

6 summer drought reduces tree growth / eq;

7 physical disturbance by recreational activities ;

8 trampling destroys {vegetation / habitats} ;

[two pairs only]

4 marks

Total 12 marks



January 2007 6106-02 Unit 6 (W2) Mark Scheme

6106-02 January 200714

Unit 6 W2 (6106-02)

Question 1 Maximum marks

(a)

Fieldnumber

Number of skylarks inplots with cutwheat stems

Mean numberof skylarks inplots with cutwheat stemsha -1

Number of skylarks in plotswith uncut wheatstems

Mean number of skylarks in plotswith uncut wheatstems.ha -1

1 0 1 0 1 1 0.6 2 1 2 1 1 1.4

2 0 0 1 0 1 0.4 0 1 0 0 0 0.2

3 2 1 3 0 1 1.4 2 3 4 3 2 2.8

4 0 0 9 0 0 1.8 5 5 4 3 2 3.8

5 3 3 2 3 2 2.6 5 2 2 2 0 2.2

6 2 1 3 2 2 2.0 3 4 3 4 1 3.07 0 1 0 0 0 0.2 2 2 2 2 1 1.8

8 0 0 0 0 0 0.0 0 0 0 1 0 0.2

9 1 2 0 0 5 1.6 2 1 1 3 2 1.8

10 8 7 6 5 5 6.2 8 9 9 5 7 7.6

neat table correctly formatted with raw data and field numbers ;

correctly labelled rows and columns with units ;

all means correct ; ; [1 error = 1 mark, 2 errors = 0 marks]

4 marks

(b) F bar chart of means for each field ;

A axes correct – scale, orientation and labelled with units ;

P data plotted correctly ;

3 marks

(c) there is no significant difference between the number of skylarks in the {cut /eq} and {uncut / control / eq} fields ;

1 mark




6106-02 January 200715

Question 1 Continued Maximum marks

(d) there is a significant difference between the number of skylarks in the{topped / eq} and {untreated / control / eq} fields /reject the nullhypothesis ;

at the 5% value ; [not just p = 0.05]

since the W value is less than (the critical value) 8 ;

3 marks

Total 11 marks




6106-02 January 200716


(a) 1. stated total number of subjects (min 10) ;

2. subjects selected to minimise at least two basic variables e.g.age/sex/health / eq / academic ability / eq ;

3. control group with no music ;

4. tests to be conducted at same time of day ;

5. testing environment standardised e.g. lighting/heating/seatingarrangement ;

6. accurate description of type of test to be administered e.g. randomword/number list/objects shown on screen etc ;

7. standardised type of music described ;

8. details of music delivery e.g. headphones/speakers at fixed distance ;

9. stated time to memorise/learn test ;

10. standard time between learning and post-test ;

11. re-test at further intervals (to measure retention) ;

12. standard method of scoring test described ;

Max 8 marks

SPG account is concise and well-organised, there is good use of technicalvocabulary and almost no spelling errors – 2 marks

there is some lack of organisation, limited vocabulary and a numberof spelling errors – 1 mark

the account lacks organisation, there is little or no technicalvocabulary and many spelling errors – 0 marks

2 marks




6106-02 January 200717


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

reference to calculation of means ;

suitable graphical format matching data and methods including correctlylabelled axes ;

reference to suitable statistical test (t or Mann-Whitney U) matched todata [accept from method] ;

stated null hypothesis [accept from method] ;

reference to use of 5% / p=0.05 confidence level ;

6 marks

(c) Limitations [sub-max 4 marks]

natural variability of human subjects makes standardising difficult / eq ;

difficult to control level of motivation/ effort put into learning / consciousattitude to test by all subjects / eq ;

response to standard type of music may vary between individuals ;

type of test measures simple memorising only / learning more complexthan simple memory / eq ;

subjects previous experience may give them advantage / disadvantage inany one type of test / eq ;

Further work

test responses to different types/volumes of music (if not in method) ;

compare effects over short-term with long-term ;

test for sex/age differences ;

test at different times of day ;

5 marks

Total 21 marks



January 2007 6106-03 Unit 6 Synoptic Mark Scheme

6106-03 January 200718

Unit 6 Synoptic paper (6106-03)


(a) (i) condensation / polymerisation ;1 mark

(ii) glycosidic / covalent ;

1 mark

(b) 1 ref. to (high) {blood pressure / hydrostatic pressure} in (glomerular)capillaries ;

2 low RMM solutes /eq ;

3 {forced out /eq} of capillaries ;

4 ref. to (high) permeability of capillaries /eq ;3 marks

(c) low RMM / only 5500 / RMM of 5500 / less than 70 000 / eq /small enough (to pass through capillary wall / pores) ;

1 mark

(d) 125 ;

cm3 min-1 / eq ;

2 marks

Total 8 marks




6106-03 January 200719


(a) 1 (stem cuttings) are genetically uniform / same genotype / eq ;

2 because they are produced by mitosis ;

3 grow / established quickly / eq ;

4 if high yielding, offspring will also be high yielding / reference toadapted to conditions /eq ;

2 marks

(b) (i) 1 they eat {roots / shoots / leaves / sap / eq} ;

2 reduce yield (of crop) ;

3 may spread diseases /eq ;

4 reduce value (of crop) / eq ;

3 marks

(ii) 1 ref. to specificity / no harm to non-target species / eq ;

2 ref. to no residues (of chemical control) / no run off /eq ;

3 no bioaccumulation / eq ;

4 no need to re-apply / self-sustaining idea/ no pest resurgence ;

5 pest unlikely to become resistant ;

3 marks




6106-03 January 200720

Question 2 Continued Maximum Marks

(c) (i) 1 mites are ectothermic /eq ;

2 temperature affects enzyme activity / eq ;

3 temperature affects metabolism (of mites) ;

4 may affect number of eggs they eat / eq ;

2 marks

(ii) number of eggs eaten increases as number of eggs increases /eq ;

credit a manipulated, quantitative comment ;

2 marks

(iii) 1 T. aripo ;

2 eats more eggs (at high prey density) (than G. annectens) / eq;

3 number of eggs eaten by G. annectens decreases at high preydensity ;

4 comparative quantitative reference ;

3 marks

Total 15 marks




6106-03 January 200721

ESSAY MARK SCHEME

Outline Scheme for Marking Essay Questions 3, 4B and 5H

Total maximum mark available: 15

11 available for Scientific content2 available for Balance2 available for Coherence

Scientific content (S)

Scientificcontent (S)

Description

11(good)

The essay demonstrates a sound understanding of the topic, contains asignificant amount of material relevant to two (or more) Units (including A2units) of the specification, and includes suitable examples where appropriate.The candidate has clearly and coherently linked together information fromdifferent parts of the specification.

9(above

average)

An above average essay, with accurate content. The essay includes a goodbalance of material from two (or more) Units (including the A2 units), andexamples where appropriate.There may be some minor factual errors.

7(average)

The essay includes relevant information from two (or more) Units (including A2units), and the candidate links together some facts and principles.Some examples are included.There may be some minor factual errors.

5(below

average)

The essay includes some generally factually accurate and relevant material,and there is some attempt to link material from more than one Unit.However, the discussion lacks details, particularly of A2 Units.

3(poor)

There are some correct facts, but the essay lacks depth and accuracy. Littleor no relevant information from A2 Units is included.

1(poor)

There are very few correct facts. The essay is generally superficial andinaccurate.

0(poor)

No correct, or relevant, information included.

Note: If a scientific content mark of 0, 1, or 3 is awarded, it is very unlikely that a

balance mark of more than 1 is appropriate.S = 11 marks




6106-03 January 200722

Balance (B)

2 Most of the main topic areas outlined are coveredSome discussion of each of the areas chosen, illustrated with suitableexamples where appropriateMaterial included is all relevant to the topic and the candidate haslinked information from more than one area of the specification.Few, if any, errors

1 Some of the main topic areas outlined are covered.Some discussion of each of the areas chosen.Some irrelevant material included.There are some examples which link together different areas of thespecification.Some errors.

0 Very limited account, possibly only one aspect chosenMaterial mostly irrelevantNo examples of the candidate linking information from different topicsLarge number of errors

B = 2 marks

Coherence (C)

2 Material logically presented, with little or no repetitionEssay has coherence, ideas are developed well; continuous prose usedthroughoutEssay has an introduction and a conclusion, summing up the mainpointsTechnical terms have been used correctlySpelling, punctuation and grammar are sound

1 Material is presented in an orderly way and some ideas developedContinuous prose used throughoutThe introduction and conclusion may be present, but brief Technical terms are used and generally in the correct contextSpelling, punctuation and grammar are generally sound

0 Essay style not usedMaterial in note form or numbered pointsVery poor standard of spelling, punctuation and grammar

C = 2 marks




6106-03 January 200723

Question 3

Introduction could include reference to liver cell as a eukaryotic cell and range of functions –

Shape of cell –

Surface membrane –

Organelles:

Nucleus + nuclear membrane -Unit 1

Endoplasmic reticulum –

Mitochondria –

Lysosomes –

Golgi apparatus –

Functions:

Deamination and urea synthesis –Unit 4

Glucose – glycogen metabolism –

Credit other relevant functions -

Scientific content 11 marksBalance 2 marks

Coherence 2 marks

Total 15 marks




6106-03 January 200724

Question 4B

Introduction could include explanation of the term pigment and the range of functions of pigments in flowering plants –

Structure of chloroplast and location of pigments – Units 1 and 5B

Detection of light by phytochrome – Units 4 and 5B

Roles of chloroplast pigments –

Chlorophyll a and b –

Carotenoids – Unit 5B

Absorption spectra –

Light dependent reactions –

Ref. to pigments in flowers in relation to insect pollination – Unit 2B

Scientific content 11 marksBalance 2 marks

Coherence 2 marks

Total 15 marks




6106-03 January 200725

Question 5H

Introduction could include reference to the significance of meiosis –

Gamete formation involves meiosis – Unit 2H

First and second divisions of meiosis –

Chiasmata formation –

Random fertilisation as a source of genetic variation –

Non-disjunction – Unit 5H

Polysomy and polyploidy –

Specific reference to Down’s syndrome –

Could also include detection of chromosome mutations and karyotypes –

Scientific content 11 marks

Balance 2 marksCoherence 2 marks

Total 15 marks



26



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January 2007

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