2004 january sn 1,2,3,4 mark scheme

GCE

Mark Schemes

Edexcel GCE

Biology (Salters-Nuffield) (Pilot) 8048 and 6134January 2004

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January 2004

Publications Code US014463

All the material in this publication is copyright© London Qualifications Ltd 2004

Contents

General Introduction p

General Information p

Mark Schemes

Unit SN1 6131 Lifestyle, Transport, Genes and Health p1

Unit SN2 6132 Development, Plants and the Environment p 12

Unit SN3 6133 paper 02 Practical Work Review p26

Unit SN4 6134 Environment and Survival p 29

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. The schemesare further amended at the Standardisation meetings attended by all examiners. TheStandardisation meeting ensures as far as possible that the mark scheme covers thecandidates' actual responses to questions and that every examiner understands andapplies it in the same way.

The schemes in this document are the final mark schemes used by the examiners in thisexamination and include the amendments made at the meeting. They do not include anydetails of the discussions that took place in the meeting, nor do they include all of thepossible alternative answers or equivalent statements that were considered to be worthyof credit.

It is emphasised that these mark schemes are working documents that apply to thesepapers 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 in thecontext of the candidates' responses and in relation to the other questions in the paper.It should nbt be assumed that future mark schemes will adopt exactly the same markingpoints as this one.

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

Unit Codes and Unit Titles

This Mark Scheme covers the unit offered in this examination for Advanced SubsidiaryBiology (Salters-Nuffield) (Pilot) 6131. The units available for the complete qualifications,Advanced Subsidiary and Advanced, are listed in the table below.

Level Unit Code Unit TitleAS 1 6131 Lifestyle, Transport, Genes and Health

2 6132 Development, Plants and the Environment

3 6133 Report and Practical Review

A24 6134 Environment and Survival

5 6135 Energy, Exercise and Coordination; Coursework Investigation

6136 Synoptic Paper

II

GENERAL INFORMATION

The following symbols are used in the mark schemes for all questions:

Symbol Meaning of symbol

; semi colon Indicates the end of a marking point

eqIndicates that credit should be given for other correctalternatives to a word or statement, as discussed in theStandardisation meeting

/ obli queWords or phrases separated by an oblique arealternatives to each other

U curly bracketsIndicate the beginning and end of a list of alternatives(separated by obliques) where necessary to avoidconfusion

() round bracketsWords inside round brackets are to aid understandingof the marking point but are not required to award thepoint

U square brackets Words inside square brackets are instructions orguidance for examiners

Crossed out work

If a candidate has crossed out an answer and written new text, the crossed out work can beignored. If the candidate has crossed out work but written no new text, the crossed outwork for that question or part question should be marked, as far as it is possible to do so.

Spelling and clarity

In general, an error made in an early part of a question is penalised when it occurs butnot subsequently. The candidate is penalised once only and can gain credit in later partsOf the question by correct reasoning from the earlier incorrect answer.

No marks are awarded specifically for quality of language in the written papers, exceptfor the essays in the synoptic paper. Use of English is however taken into account asfollows:

• the spelling of technical terms must be sufficiently correct for the answer to beunambiguouse.g. for amylase, 'ammalase' is acceptable whereas 'amylose' is note.g. for glycogen, 'glicojen' is acceptable whereas `glucagen' is note.g. for ileum, 'illeum' is acceptable whereas 'ilium' is note.g. for mitosis, 'mytosis' is acceptable whereas 'meitosis' is not

• candidates must make their meaning clear to the examiner to gain the mark.

• a correct statement that is contradicted by an incorrect statement in the same part of ananswer gains no mark — irrelevant material should be ignored.

January 2004 6131 Unit SN1 Mark Scheme

Unit SN1 (6131)

Question 1 Maximum mark

(a) 1. Compact / eq ;

2. {Polymer / eq} of glucose ;

3. Can be (easily) hydrolysed / can be broken down to release energy ;

4. Insoluble / does not affect osmosis / eq ;

5. Will not diffuse out of cells / will remain in cells ;2 marks

(b) (i) Correct glucose structure for each molecule where the reaction is takingplace ; ;

2 marks

(ii) Hydrolysis ;1 mark

Total 5 marks

1



(a) (i) Entrapment in {alginate / gel) (beads / matrix) / eq ;1 mark

(ii) Enzyme more stable / eq ;

Product not contaminated with enzyme / less down stream processing toremove enzyme ;

Enzyme can be reused ;

Allows a continuous process ;2 marks

(b) {Sucrose / other disaccharide) {doesn't fit / is the wrong shape / differentstructure I eq} ;

Only lactose can fit! eq ;

Reference to lactase active site ;2 marks

Total 5 marks

2


Question 3

Maximum mark

(a) [Points must be comparative]

Arteries Veins

More (smooth) muscle / eq Less (smooth) muscle

More elastic {fibres / tissue) / elastin Less elastic {fibres / tissue)

No valves (except aorta andpulmonary artery) Valves present

Narrow lumen / eq Wider lumen

Thick layer of collagen (fibres) / eq Thin layer of collagen fibres

Thick wall Thin wall

3 marks

(b) Higher (blood) pressure / more chance of damage to endothelium ;1 mark

(c) High {hydrostatic / blood) pressure ;

Which is higher than {solute potential gradient / eq) / correct osmotic effectdescribed ;

(Plasma forced out) through (pores / gaps) in capillary wall ;

The fluid is forced out of the capillary into the intercellular space ;2 marks

(d) Blocked lymph vessels / high blood pressure / {low solute potential / highwater potential} in blood / loss of plasma proteins / damage to tissue /histamine / eq ;

1 mark

(ii) Oedema ;1 mark

Total 8 marks

3

January 2004

Question 4

(a) Parents Hh and hh ;

6131 Unit SN1 Mark Scheme

Maximum mark

Gametes of each parent shown ;

Correct genotypes of offspring Hh and hh ;

Probability 50% / 1 in 2 / 0.5 / eq ;4 marks

(b) (i) Level one answers — introduce a relevant idea

1. Reduce risk of heart disease ;

2. Allows early medical intervention / prenatal testing / abortion / decision not tohave children ;

3. Allows a change in lifestyle ;

4. Able to reduce risk factors ;

5. Named risk factor ;

The mark scheme for level two answers continues on the following page.

4


Question 4 continued Maximum mark

(b) (i) Level two answers — develops and qualifies the ideas

6. Able to monitor cholesterol levels ;

7. Take diuretic drugs / sympathetic nerve inhibitors — lowers blood pressure ;

8. Use beta-blockers — reduces heart rate and blood pressure ;

9. Use (anticoagulant / platelet inhibiting drugs! clot busting drugs) — reducesthe risk of a clot forming

10. Eat less salt — to reduce blood pressure ;

11. Have a low fat diet / reduce intake of cholesterol / take {stanins / stanols /other cholesterol lowering drugs} [have a more balanced diet /-eat lesssaturated fat / eat more fibre / eq — prevents the build up of (fatty plaques /atheromas / atherosclerosis / narrowing arteries) ;

12. Eat five portions of fruit or vegetables a day / take vitamin supplements / takeantioxidants — prevents cellular damage due to free radicals ;

13. Exercise more - to increase strength of cardiac muscle / make heart stronger/ help prevent build up of {atheroma / fatty plaques} / reduce fat (burns fat)!reduce BMI / reduce risk of obesity! eq ;

14. Stop smoking — to reduce (nicotine! free radical) levels ;

15. Reduce stress — lowers blood pressure ;

16. Avoid heavy drinking — avoid risk of damaging (heart tissue! liver tissue)!reduce LDL production ;

[If there are level one answers only, allow a maximum of two marks]

4 marks



Depression / stressORCost of screening to NHS / eqORProblems with life insurance company / confidentiality / eqORMay decide not to have children / increased number of abortions / increasedchance of miscarriage / ethical {considerations / issues) (related to testing /abortion) / problems of false {negative / positive) results ;

1 mark

Total 9 marks

6

January 2004


Question 5

Maximum mark

(a) (Ventricular) systole / ventricular contraction ;1 mark

(b) (As ventricle contracts) pressure increases ;

From 2.0 -4.0 kPa Ito {14.0 /15.0) kPa ;2 marks

(c) X Point when pressure in ventricle first exceeds pressure in atrium ;

Point when pressure in aorta first exceeds pressure in ventricle ;

[allow marks if X and Y both placed on the X axis at the correct times]2 marks

(d) (60 ÷ 0.8) = 75 ;

Beats per minute / bpm ;2 marks

7



(e) (i) Same pattern as normal ECG;

More than one cycle in the grid ;2 marks

(ii) They may have been {exercising / stressed / eq} / genetic variation / age /fever / body temperature / stimulant / excitement ;

1 mark

(iii) 1. Measure (ECG) under physical exercise (treadmill) ;

2. Blood pressure check ;

3. Measure blood cholesterol ;

4. Ultrasound ;

5. Calculate BMI ;

6. MRI ;

7. CAT / CT / EBCT ;

8. {Ambulatory /24 hour} monitoring ;

9. Coronary {angiography / angiogram} ;2 marks

Total 12 marks

8

January 2004


Question 6

Maximum mark

(a) (i) W Guanine / G;

X Nucleotide ;

Y Phosphate / phosphoric acid ;

Z Deoxyribose / pentose sugar / 5C sugar ;4 marks

(ii) Hydrogen ;1 mark

(b) (i) Transcription1 mark

(ii) Aspartic acid, Arginine, Cysteine, Lysine ;1 mark

(iii) 1. Incorrect amino acid inserted into polypeptide chain / {chain / sequence) ofamino acids changed ;

2. Named (Gly / glycine) ;

3. Different (side group / R group I eq) ;

4. Different bonds formed ;

5. Different (3D) shape when folded / ect3 marks

Total 10 marks

9

10

January 2004


Question 7

Maximum mark

(a) Restriction / endonuclease ;1 mark

(b) 1. Use of {agarose / polyacrylannide} gel ;

2. DNA loaded into wells / description ;

3. Use of a buffer ;

4. {pd / current} applied ;

5. (Negatively charged) DNA moves to (positive) electrode ;

6. DNA fragments move according to {charge / size} / {smaller go further orfaster! converse} / eq ;

7. Transfer DNA to {nylon / nitrocellulose} (paper) / southern blotting ;

8. DNA strands separate (exposing base sequences) / single stranded / use ofalkali

9. Gene probe with complementary sequence ;

10. {Binds / eq} to faulty gene ;

11. Use of {radioactive / fluorescent} labelling ;

12. Use of imaging technique (e.g. X-ray, UV, laser) ;

[allow mark points under either section (i) or (ii). Maximum 6 marks]6 marks



(c) (i) 1. Chloride (ions) {cannot leave / retained by} cell / eq ;

2. Correct reference to sodium ions ;

3. {Decreases water potential / increases solute concentration} inside cell / eq ;

4. Water (diffuses / moves) into cell / water leaves the mucus ;

5. By osmosis ;

6. Therefore less water in mucus / eq ;3 marks

(ii) {Bacteria / pathogen / microorganism} trapped in sticky mucus / antibodiesinactivated ;

1 mark

Total 11 marks

11


Unit SN2 (6132)


Endoplasmic reticulum / mitochondrion / mitochondria / membrane-boundorganelles / internal membranes ;

1 mark

(ii) Bacterium! named bacterium / bacteria / blue-green algae -I cyanobacteria ;1 mark

(b) (i) Ribosome ;

(ii) Protein synthesis ;

OR

( I) (Rough) endoplasmic reticulum / intermembranal space ;

(ii) {Transporting / trafficking / folding! synthesising} proteins ;2 marks

(c) B (Outer mitochondria!) membrane / double membrane! intra-membranal space! double envelope ;

Crista / infokling of (inner mitochondria!) membrane / innermitochondria! membrane ;

2 marks

Total 6 marks

12

January 2004


Question 2

Maximum mark

(a) 1. Tail / flagellum ;

{To swim / to propel it) to the {egg / ovum / vitelline membrane};

2. Small(er) size ;

Makes it easier for it to swim Ito aid mobility / makes it possible to producethem in large numbers ;

3. Haploid number of chromosomes / only one of each chromosome / (only) 23chromosomes rather than 46;

So {normal /diploid) number restored at fertilisation ;

4. Acrosame / sac of enzymes ;

To digest way (in)to egg ;

5. Mitochondria ;

Energy for swimming / eq ;4 marks

(b) (Mitosis and) meiosis ;1 mark

(c) (Produces) {biological / genetic} variation ;

No two sperms the same ;

Many sperms do not reach egg / increases chances of fertilising eggs ;

Selection for {fittest / eq} sperm ;

Some sperms defective ;2 marks

Total 7 marks

13

January 2004


Question 3

Maximum mark

(a) Vacuole ;

Tonoplast ;

Plasmodesmata / plasmodesma ;

Pits ;

Chloroplasts / plastids ;

Starch grains / amyloplast ;

Calcium pectate qualified / middle lamella ;3 marks

(b) (i) P Sclerenchyma / (wood) fibres ;

(xylem) vessel (cell / element) ;2 marks

(ii) 1. Cellulose microfibrils held together by hemicelluloses ;

2. Reference to orientation of microfibrils to give maximum support in stateddirection ;

3. Reference to H-bonds ;

4. Lignification makes walls (stiffer / rigid / thicker} ;

5. Cellulose walls are thicker /-secondary cellulose ;3 marks

14



Paper production / (production of) {cloth / fishing nets / fabric} /biocomposites / ropes / string / animal feed / biofuel / fermented to makebiogas / green manure ;

1 mark

(ii)

Nettles will regrow after stems have been harvested / harvest seeds and sowfor new crop / no need to buy seeds / idea that one can always grow more

(as opposed to) use of non-renewable resource / named non-renewableresource e.g. oil / if used as (bio)fuel {carbon dioxide output is equal tocarbon dioxidelnput / carbon neutral} ;

Not causing deterioration of (good) agricultural land / eq ;2 marks

Total 11 marks

15



(a) Remote sensing / satellite (images)! GIS / Global imaging system / OTCS ;

1 mark

(b) (Algae supply polyps) with {sugar / carbohydrates / energy / food} ;

(Algae supply polyps) with oxygen ;

Any credible suggestion why colour is an advantage to the polyp ;2 marks

(c) 1. Some (species of) coral become less common / other types become morecommon (and take over)

2. Reference to competition ;

3. Existing species {become adapted to change / evolve} ;

4. Correct reference to mutation ;

5. Improved conservation measures (to alleviate effects of human interference)

6. Increased sea temperature was not the real reason why the reef was indecline suggested credible alternative e.g. {pollution / predation / disease} /whatever the original cause {has now declined / no longer the problem itwas} ;

2 marks

Total 5 marks

16



(a) Genes inaccessible (to substances that might induce them) / genes cannotbe {switched on / induced);

Therefore {transcription / mRNA synthesis} {prevented / cannot take place} ;2 marks

(b)

All {male gametes / sperms} Z / gets Z from father ;

{Egg cells / female gametes / ova} have hat, W / female bird gets W from hermother ;

{Equal / similar} probability of ZZ or ZW/ (approximately) {50% / 50-50 / 1:1ratio} {chance / probability} of getting ZVV ;

2 marks

(c)

By temperature ;

(Temperature) at which eggs incubated / eq ;

Males produced at medium temperature / females produced at high and lowtemperatures ;

3 marks

Total 7 marks

17

January 2004


Question 6

Maximum mark

(a) (Lipid has) high energy value / eq ;

To provide {nutrition / energy} (for the seed / embryo) ; [do not allow food]

(To provide energy) for {growth / development / germination / eq} ;

Until photosynthesis2 marks

(b) Reference to {seed dispersal / seeds dispersed} / eq ;

Only a proportion of the seeds {mOved around / hidden / collected} areactually eaten ;

Prevents overcrowding / colonisation of new areas / reference to competition

2 marks

18



(c) (i) Induction ;1 mark

(ii) Gibberellic acid {produced / activated} when seed exposed to cold ;

{Switches on / induces} (lipase) gene ;

Correct reference to transcription ;

Removes {inhibitor / repressor};2 marks

(iii) 1. mRNA leaves the nucleus ;

2. Reference to {codon / anticodon} ;

3. Amino acids {joined / condensed) ;

4. On ribosomes ;

5. Amino acid sequence determined by base sequence (of RNA / DNA) ;

6. Any correct reference to tRNA ;3 marks

Total 10 marks

19

January 2004


Question 7

Maximum mark

(a) Access for {pollinators / pests / parasites} ;

Wind exposure ;

Light intensity ;

Light spectral composition ;

Wavelength / spectral composition of light ;

Rainfall / snow cover / soil moisture / water availability ;

Grazing by animals ;

Humidity / wafer vapour ;

{Carbon dioxide / oxygen} concentration ;3 marks

(b) (i) Dendrochronology ;1 mark

(ii) Increases ;

Any valid attempt to quantify the increase in growth e.g. more than double, atleast x5 (or more) ;

Sustained-for (at least) three years (at a similar rate) ;2 marks

(c) . Pollen analysis / use of pollen from peat ;

Layers dated according to the depth / the deeper the {sediment / peat layer}the older the specimen / date the peat layer by radiocarbon method ;

Identify species in different layers / estimating relative abundance from pollendensity / eq ;

2 marks

20



(d) More carbon dioxide turned into wood / more photosynthesis ;

Therefore more carbon dioxide removed from atmosphere / increased carbondioxide absorption ;

Therefore less greenhouse gas (than there otherwise would be) ;2 marks

(e) Increased rate of decay ;

Due to increased {microbial activity / enzyme activity} ;2 marks

Total 12 marks

21



(a) (i) Allows the (easy) introduction of {genes / DNA) into a plant (cell) ;-1 mark

(ii) Plasmid is a circular piece of DNA;

Separate from main chromosome / eq ;

New {gene / DNA) can be {attached / incorporated) into plasmid ;

Plasmid can pass from bacterium into plant cell (carrying new gene) ;2 marks

(b) DNA gun / particle gun ;

Using a virus to infect the plant ;2 marks

(c) A plant cell with the cell wall removed / no cell wall present ;1 mark

(d) (i) Cell division / meristematic activity ;

Cell differentiation / reference to named cell types being made ;

Mitosis ;2 marks

(ii) {Rapid / cheap} production of many plants ;

All from the same callus / with the same genotype ;

All incorporating genetic modification ;

Carried out in {disease free / sterile) conditions ;

Easy distribution of plantlets ;2 marks

Total 10 marks

22



(a) Up to three marks for mentioning three of the following points with anadditional mark for the qualification in each case up to a total of 6 marks forthe whole section

1. An issue about antibiotic resistance ;

Antibiotic markers could lead to antibiotic resistance in (human) (pathogens /microbes / bacteria) ;

2. May cause allergies ;

Possible example of such an allergy / attempt to describe what is meant byan allergic response ;

3. Could make crop harmful to consumers ;

Reference to presence of possible toxic substances ;

4. May (affect! spread-to) (other (non-GM) crops / wild plants) ;

Pollen may spread to {non-GM / organic farms} / may transfer herbicideresistance to other {weeds / wild plants) ;

5. Loss of genetic diversity Iincreased reliance on fewer and fewer strains ;

(World's human food supply) vulnerable to {climate / environmental) change /newly emerged {disease / pathogen) of the crop plants ;

6. International biotech companies cannot be trusted ;

Could make developing world / the world in general too dependent on a smallnumber of suppliers / issues too complex for public to understand thereforeeasily misled ;

7. Inadequate testing of GM products ;

Until the recent concern many GM products were released onto the marketuntested / adequate international protocols for testing do not exist ;

23



8. GM may have unforeseen {environmental / medical} consequences ;

Reference to the precautionary principle / (the risk may be small) but thedangers could be too catastrophic to take the risk! when we find a problem itcould be too late ;

9. {Ethical / religious} objections to tampering with nature / GM difficult tocontrol / current research might be harmless but where will it all lead? ;

Economic factors may force people to adopt GM to compete (even if they areopposed to it) / (in the wrong hands) risks of promoting {biological warfare /eugenetics / designer babies} ;

6 marks

(b) Up to four marks from the following marking points

1. This is a means of addressing some very serious problems / in developingworld {problems are too serious! it is unethical / immoral} to ignorepossibilities of GM;

2. Including vitamin A deficiency / malnutrition ;

3. Blindness ;

4. Many developing countries have already welcomed the proposal ;

5. Ways of testing GM products for safety {do exist! could be developed} /international {protocols / agreements} on GM could be developed / testingcan be undertaken successfully / testing so far has found only limited risksfrom GM / many countries have been using GM for years ;

6. May lead to new scientific discoveries / there are likely to be even moreuseful developments from GM if we {allow / do not discourage} research ;

7. a relatively {easy / cost effective} form of foreign aid — cheaper thansupplying vitamin tablets and treating blindness ;

24

January 2004


Question 9 (b) continued

Maximum mark

Two additional marks from the following marking points

8. It is possible to use antibiotic resistant genes for antibiotics which are nolonger used medically / possibility that we could detach antibiotic genes fromtransgenic organism once development is complete ;

9. The potential of GM is so great that some risks e.g. the risks of {starvation /blindness / human suffering) are worth taking ;

10. Illogicality_of accepting products of conventional plant and animal {breeding /artificial selection) whilst regarding GM as too dangerous! products fromconventional (plant and animal) breeding are not always tested and yet theyare regarded as 'natural' / hysteria about dangers of GM seems {out ofproportion to / detracts from) other better documented risks such as {obesity /political instability in developing countries) ;

11. If the people can get the vitamin from vegetables why aren't they doing italready? / GM is more effective than having an 'eat vegetables' campaign ;

12. Why can't you trust GM companies? Not in the biotech industry's interest toput people at risk !biotech industry has self-regulation / it is fair enough tocounteract misleading environmentalist propaganda ;

6 marks

Total 12 marks

25

January 2004 6133/02 Unit SN3 Mark Scheme

Unit SN3 Practical Review (6133/02)


(a) 1. Is the use of living things justified / animals cannot give consent ;

2. Need to minimise {suffering / harm} to animals / need to return to naturalhabitat ;

3. Benefits of use outweigh ethical considerations ;

4. Religious objections ;2 marks

(b)

Accuracy

1. Detail of apparatus with appropriate level of accuracy ;

2. Detail of technique (e.g. dots on paper, video, stroboscope — for Daphnia,reference to blank or zeroing between readings with colorimeter) ;

Reliability

3. Repetition / replication ;

4. Dealing with anomalies ;

5. Controlling variables ;

6. Appropriate comment about {objectivity / subjectivity / qualitative /quantitative / bias} ;

4 marks

Total 6 marks

26

January 2004

6133/02 Unit SN3 Mark Scheme

Question 2

Maximum mark

(a) Graph

1. Type of graph related to type of data ;

2. Reference to clarity of trends or patterns / allows anomalies to be identified ;

3. Choice of scale ;

4. Correct axis for each variable (independent variable on x axis / dependentvariable on y axis) ;

5. Use of error bars to show {variation / range / standard deviation / standarderror} of results ;

Table

6. Independent variable in first column ;

7. Each column headed with appropriate title ;

8. Units with titles not with data ;

9. Additional columns for calculations e.g. (rates / percentages / means};3 marks

(b) (1) Appropriate method of control of two named variables ; ;2 marks

(ii) 1. Correct link between variable and its effect on the results (e.g. temperatureaffects amount of product) ;

2. Direction of effect on dependent variable correctly explained (e.g. increasingtemperature increases amount of product) ;

2 marks

Total 7 marks

27

January 2004

6133/02 Unit SN3 Mark Scheme

Question 3

Maximum mark

(a) (i) 1. Systematic error is where all values differ from the true value by the sameamount / eq ;

2. Random error is where values lie equally above or below an average value /eq ;

2 marks

(ii) 1. Correctly identifies a source of systematic error (e.g. wrong colour filter usedto calibrate a colorimeter)

2. Explains how systematic error affects results (e.g. all results too high or toolow) ;

2 marks

(b) 1. Reference to the {range / standard deviation / standard error} of results / useof error bars ;

2. Considers extent of error (large range means large degree of error) / difficultto find {trend / pattern);

3. Effect on significance (larger the degree of error the less significance) ;

4. Reference to large {set of results / sample} being more representative:

5. Awareness of accuracy or error in {apparatus /technique} ;3 marks

Total 7 marks

28


Unit SN4 (6134)


(a) 1. Changes in {tree species / communities / eq} with time ;

2. Seral stages / predictable changes / directional changes / eq ;

3. Changes bought about by trees themselves / eq ;

4. Reference to climax ;

5. Relevant example from the data ;2 marks

(b) 1. None at outset ;

2. Biomass increase (with time) ;

3. Fall after 200 years ;

4. Greatest rate of increase between 80 and 120 years ;

5. Any other quantitative description ;3 marks

(c) 1. Soil conditions not suitable / lack of water / lack of minerals / other abioticfactor ;

2. Cannot compete with {alder / willow} ;

3. Didn't happen to colonise ;

4. Other {climatic / external} factor ;

5. Species before (Hemlock spruce) change conditions ;2 marks

Total 7 marks

29



(a)

Answers must be appropriate to a named organism — maximum two marks iforganism not named

1. Method for defining samples (eg quadrat) ;

2. Method for quantifying organisms (eg counting individuals, percentagecover) ;

3. Method for selecting samples (eg transect, random or systematic sampling) ;

4. Method for fixing samples (eg random numbers, fixed point above chartdatum) ;

5. Additional detail of equipment used ;

6. Additional appropriate practical detail (eg running means, repeats) ;4 marks

(b) (i) Mussels (not found / found less) {outside stream / in sea water} / converse ;

Reference to greatest number of mussels in middle of stream / eq /converse ;

Numerical calculation comparing outside stream with in stream, allowbetween 5 and 6 times as many ;

2 marks

(ii) 1. Mussels (cannot tolerate / tolerate less well) {salt water / high salinity) /tolerate fresh water better ;

2. Mussels which begin development in sea water don't survive ;

3. Hidden from predators ;

4. Can feed for longer! food (only found / found more) in stream / can openshell to feed in fresh water ;

5. Cooling effect from stream ;

6. Cannot tolerate dry period between tides / need to be in water continuously ;

7. Less affected by wave action / better attachment to {substrate / rocks / eq) ;2 marks

30

January 2004 6134 Unit 5N4 Mark Scheme


(c) 1. Dog whelks can only survive in saltwater;

2. Therefore very few present at sites 3, 4 and 5;

3. Dog whelks in sea water feed on mussels ;

4. Not enough time between tides to eat a mussel ;

5. Reference to explanation of the one dog whelk at site 3;

6. Identify one biotic or abiotic factor in context ;3 marks

Total 11 marks

31

January 2004

Question 3

(a) (i) 1.9 (x 104) —1.1 (x 104)

= {0.8 x 104 / 8000} kJ re yr-1

(ii) 0.1 0.8 x 100;

= 12.5%;


Maximum mark

2 marks

2 marks

(b)

Some used in plant respiration ;

Not all parts of plants {eaten / available} ;

Indigestible matter / cellulose / plant cell walls / faeces / excretion ;

In {heat / respiration} of 1° consumers ;2 Marks

Total 6 marks

32

January 2004


Question 4

Maximum mark

(a) Cell wall ;

Cell membrane ;

Ribosome ;

Mesosome ;

Cytoplasm ;

Some organelles ;

Correct reference to DNA as genetic material / reference to RNA in viruses ;

Bacterial cell much larger (must be comparative):

Any other TWO correct differences: ;2 marks

33



(b) (i) (0)3:00 / 3 a.m.1 mark

(ii) 1. Rise in temperature detected ;

2. After 7 hours / after midnight / eq ;

3. By {themnoreceptors / hypothalamus} ;

4. Stimulates effectors ;

5. Reference to sympathetic nervous system ;

6. Sweat glands / sweating / vasodilation / lethargy / hair erector muscles Letc ;

7. (More) heat lost ;

8. Less heat generated ;

9. (Body / blood) temperature falls ;

10. Reference to heat loss mechanisms switched off ;

11. Back to normal {at 10:00 / after 17 hours} ;

12. Negative feedback means rise in temperature causes fall in temperature]eq ;

5 marks

(iii) 1. Persistent coughing ;

2. Blood in {sputum / eq} ;

3. Shortness of breath ;

4. Loss of appetite / weight loss ;

5. Fatigue ;2 marks

34



(c) 1. Mutation of bacteria ;

2. Vaccines less effective ;

3. Decreased availability of vaccination ;

4. Less rigorous vaccination programme ;

5. Reference to plasmids ;

6. Antibiotic resistance developing ;

7. Misuse of antibiotics ;

8. Increased travel / migration ;

9. Increase of HIV;

10. {Confined / crowded / overcrowded} areas qualified, with reference todisease transmission

2 marks

Total 12 marks

35



(a) Teeth decay slowly / teeth less likely to {decay / break down} / dental historyunique to individual ;

1 mark

(b) 1. DNA in hair (cells) ;

2. DNA unique to individual ;

3. Produce {DNA fingerprint / pattern of DNA fragments} ;

4. Reference to {digestion of DNA / restriction enzymes} ;

5. Reference to {separation of fragments! electrophoresis} ;

6. Reference to comparison with {relatives / existing records} ;

7. Reference to PCR / amplification of DNA ;3 marks

(c) 1. Body core temperature ;

2. Rigor mortis / degree of muscle contraction ;

3. Decomposition / colour of body / bloating of body ;

4. Entomology / number and types of insects found ;

5. Succession {qualified / description / eq} ;2-marks

Total 6 marks

36



(a) 1. (HIV proteins act as) antigens ;

2. Stimulate immune response / antibody production by B cells ;

3. Clonal selection by the antigen / eq ;

4. B cells {proliferate / clone / divide / clonally expand / undergo mitosis) ;

5. To plasma cells ;

6. (Plasma cells) {produce / eq} (specific) antibodies ;

7. Reference to antigenic presentation ;4 marks

(b) 1. Not much effect in first few years ;

2. Number of T helpers falls (with time) ;

3. Reference to role of cytokines ;

4. Less able to {respond to antigen / mount immune response / eq}/ not enoughcytokines produced ;

5. More difficult to prevent infection ;

6. Health deteriorates / more infectious illness / opportunistic infection /example ;

7. Reference to T cells going below 200;

8. Reference to AIDS;

9. Death likely ;4 marks

Total 8 marks

37

January 2004

Question 7

(a) The populations don't interbreed ;


Maximum mark

1 mark

(b) 1. {Changes / mutations} in {DNA / genes / alleles} ;

2. Accumulate in populations / changes of gene frequency / eq ;

3. Over production of offspring / many {offspring / eggs} ;

4. Competition (for a resource) ;

5. Better adapted {survive / reproduce} ;

6. Advantageous {alleles / characteristics} are inherited ;

7. Different selection pressures (in each population) ;

8. Different characteristics benefit each population ;

9. (Genetic / characteristic / phenotype) differences (between populations)become greater over time ;

10. Hybrid offspring infertile ;

11. Incompatible genomes / chromosomes become different / meiosis fails inhybrid ;

12. New species when (mating between the two populations) can't produce fertileoffspring

13. Reproductive or temporal isolation ;

Biological content - maximum 6 marksContinuous prose - 1 mark

7 marks

38



(c) 1. Religious beliefs not compatible ;

2. Explanation of incompatibility / reference to creationism ;

3. Lack of evidence / incomplete fossil record ;

4. Impossible to experiment because time scale too big / theory not fact ;2 marks

Total 10 marks

39

Order Code US014463 January 2004

For more Ines/nation on Edexcel qualifications please contact ourCustomer Response Centre on 0970 240 9800or emelt M1k1251105202,1115or visit our waste: sem edexcel org.uk

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Further copies of this publicalion a. mallet* fromEdexcel Publications, Adamsway, Mansfiekl, Notts, NG18 4LN

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2004 january sn 1,2,3,4 mark scheme

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