2006 january sn 1,4 mark scheme

advancing teaming, changing Lives

Mark Scheme

GCEEdexcel GCE

Biology (Salters-Nuffield)

6131 Et 6134

January 2006

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January 2006Publications Code UA 017362All the material in this publication is copyright0 Edexcel Ltd 2006

Contents

General Introduction p

Unit Codes and Unit Titles p iii

General Information p iv

Mark Schemes

Unit SN1 6131 Lifestyle, Transport, Genes and Health

p1

Unit SN4 6134 Environment and Survival p8

GENERAL INTRODUCTION

Mark schemes are prepared by the Principal Examiners and revised, together with the relevantquestions, by a panel of senior examiners and subject teachers. The schemes are furtheramended at the Standardisation meetings attended by all examiners. The Standardisation meetingensures as far as possible that the mark scheme covers the candidates' actual responses toquestions and that every examiner understands and applies 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 any detailsof the discussions that took place in the meeting, nor do they include all of the possiblealternative answers or equivalent statements that were considered to be worthy of credit.

It is emphasised that these mark schemes are working documents that apply to these papers in thisexaminatiom Every effort is made to ensure a consistent approach to marking from oneexamination to another but each marking point has to be judged in the context of the candidates'responses and in relation to the other questions in the paper. It should not be assumed that futuremark schemes will adopt exactly the same marking points as this one.

Edercel cannot under any circumstances discuss or comment informally on the marking ofindividual scripts. Any enquiries about the marks awarded to individual candidates can bedealt with only through the official Enquiry about Results procedure.

Unit Codes and Unit Titles

This Mark Scheme covers the units offered in this examination for Advanced Subsidiary Biology(Salters-Nuffield), 6131 and for Advanced GCE Biology (Salters-Nuffield), 6134.

The units available for the complete qualifications, Advanced Subsidiary and Advanced, are listedin 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

6 6136 Synoptic Paper

Please note that Units 6132, 6133, 6135 and 6136 are only available in the Summer examinationseries.

lii

General Principles

Symbols used in the mark scheme

Symbol Meaning of symbol

; semi colon Indicates the end of a marking point.

eq

Indicates that credit should be given for other correct alternatives to aword or statement, as discussed in the Standardisation meeting. It isused because it is not always possible to list every alternative answerthat a candidate may write that is worthy of credit.

/ oblique Words or phrases separated by an oblique are alternatives to eachother.

D curly brackets Indicate the beginning and end of a list of alternatives (separated byobliques) where necessary to avoid cur i usion.

0 round brackets Words inside round brackets are to aid understanding of the markingpoint but are not required to award the point.

0 square brackets Words ienside square brackets are instructions or guidance for

examinrs.

Crossed out work

If a candidate has crossed out an answer and written new text, the crossed out work can be ignored.If the candidate has crossed out work but written no new text, the crossed out work for that questionor 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 but notsubsequently. The candidate is penalised once only and can gain credit in later parts of thequestion by correct reasoning from the earlier incorrect answer.

No marks are awarded specifically for quality of language in the written papers, except for theessays in the synoptic paper. Use of English is however taken into account as follows:

• the spelling of technical terms must be sufficiently correct for the answer to be unambiguouse.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 partof an answer gains no mark- irrelevant material should be ignored.

iv

MARK SCHEME - UNIT SN1 (6131)AS BIOLOGY (SNAB) January 2006

Question 1

Maximum Mark

(a)

Chemicalcompound

One example of thechemical compound

found in living organisms

Subunit(s) of thechemical

Elementscontained inthe chemical

PolysaccharideStarch / Glycogen /

Cellulose / Amylose /Amylopectin;

Monosaccharide /Glucose / named

monosaccharide egglucose;

C,H2O;

ProteinEnzyme Amino acid; C,H2O,N,S

Lipid PhospholipidFatty_acids_and

Glycerol; C,H,0

Nucleic acid DNA/RNA; Nucleotide C,H2O,N,P

7 marks

(b) Unsaturated contain one or more (C=C) double bonds / eq;1 mark

(c) Diagram showing a bilayer of phospholipids;

Heads on outside and tails on inside [Must have two tails];

Proteins included in the diagram; [distinguishable from the phospholipids, can beintrinsic, extrinsic or transmembrane with suitable label]

3 marks

Total 11 marks

N25415A Page 1 January 2006 6131

Maximum Mark

1 mark

2 marks

Question 2

(a) A change or damage to a gene / DNA / chromosome / allele /change in base sequence (on DNA);

(b) (i) Parents' phenotypes: normal / unaffected and normal / unaffected;[Reject carrier]

Parents' genotypes: Tt and It;

Genotype Phenotype Frequency

TT normal 1 / 1/4 / 25%

Tt normal 2 / i / 50%

tt thalassemia 1 / 1/4 / 25%

Phenotypes correctly assigned; [Allow carrier e.c.f.]

Frequencies correctly given;2 marks

(iii) 3 in 4 / / 75% / 0.75;1 mark

(iv) Genetic screening / amniocentesis / chorionic villus sampling / IVF /embryo screening;[Allow genetic testing]

1 mark

Total 7 marks


Question 3

Maximum Mark

(a) (

0.14% / 0.07% per year;1 mark

(ii) 3.9 - 4 times;1 mark

(b) (i) The greater the BMI the greater the chance of dying due tocoronary heart disease / eq;

Correct reference to figures;2 marks

(body)mass( in kg) (ii) BMI -

1 mark

(iii) 1. Fatty deposits in arteries / atheroma / plaques /reference to atherosclerosis;

2. Higher cholesterol levels;

3. Higher blood pressure;

4. Risk of damage to (coronary) arteries;

5. Risk of blood clot blocking coronary arteries;

6. Risk of type II diabetes;3 marks

Total 8 marks

height 2 (in metres)

1125415A Page 3 January 2006 6131

Question 4 Maximum Mark

(a) (i) Heart is visible / transparent organism / reference to ethical issues / eq;1 mark

(ii) 1. Temperature;

2. Volume of solution;

3. Daphnia (same age / growth conditions} / eq;

4. Time in solution prior to counting heart rate / eq;2 marks

(iii) 1. Very active / high metabolic rate;

2. Supplies oxygen / removes CO2;

3. Slow diffusion (through body surface) / diffusion insufficient / eq;

4. Low SAN ratio / eq;2 marks

(b) 1. Will increase blood pressure;

2. Risk of damage to arteries;

3. Increase risk of heart attack / stroke / aneurysm;

4. More chance of atherosclerosis / eq;

5. Vasoconstriction / eq;2 marks

Total 7 marks



(a)

1. Oxygen (from alveoli) to capillary and carbon dioxide (from capillary) toalveoli;

2. By diffusion /movement of molecules from area of high concentration to an area of lowconcentration / eq;

2 marks

(b)

1. Large surface area / lots of alveoli;

2. Large surface area of capillaries / eq;

3. Thin alveoli walls;

4. Thin capillary walls;

5. [Circulation of blood / ventilation of lungs} to maintain concentrationdifference;

6. Short diffusion pathway;3 marks

(c) (i) 1. CFTR (protein channel) does not work / eq;

2. Lack of a ions transported into mucus / eq;

3. Water does not move into mucus by osmosis / eq;2 marks

(ii) 1. Mucus blocks airways/bronchioles/alveoli / eq;

2. Reduces surface area for gas exchange / diffusion;

3. Less oxygen (diffuses) into blood / eq;

4. Long diffusion pathway;2 marks

Total 9 marks



(a) (i) Relates to the sequence of amino acids / eq;1 mark

(ii) 1. Reference to R groups;

2. Reference to (specific) folding of the chain / tertiary structure / eq;

3. Reference to named bonds [not peptide];2 marks

(b) 1. Enzymes have a (specific) active site;

2. Will only fit substrate with the correct shape / eq;

3. Reference to lock Et key / enzyme-substrate complexes / induced fit;2 marks

(c) 1. Correct reference to translation;

2. mRNA lines up at the ribosome / eq;

3. tRNA attaches to specific amino acids / eq;

4. Codon - anticodon binding /complementary base pairing between mRNA and tRNA;

5. Peptide bond;

6. Correct reference to start / stop codons;

4 marks

Total 9 marks


Question 7

Maximum Mark

(a)

Description of the stages for gene therapy:sequence of stagesfor gene therapy:

Plasmids inserted into Liposomes. 4

Gene for CFTR protein isolated using a restriction enzyme. [1]

Liposomes enter cells of lung tissue; normal allele isexpressed.

6

Plasmid cut with the same restriction enzyme._ 2

Normal CFTR gene inserted into plasmid using DNA ligase 3

Liposomes taken as nasal spray. 5

All 5 correct - 4 marks,3 correct - 3 marks,2 correct - 2 marks,1 correct - 1 mark.

4 marks

(b) Cells (lining the lung die and) need to be replaced /replacement cells do not contain the new gene /eq;

1 mark

(c) (i) 1. Germ line gene therapy affects gametes / gamete producing cells;

2. Somatic gene therapy affects body cells;

3. Somatic gene therapy cannot be passed onto next generation /converse;2 marks

(ii) 1. Idea of germ line gene therapy affecting every cell in the body;

2. Germ line gene therapy can pass genes on to next generation / eq;

3. Future generations unable to give consent;

4. May result in designer babies / eugenics / can cause new mutations;

[Allow converse - somatic gene therapy will not cause new genes to be passed ontothe next generation/eq]

2 marks

Total 9 mark


MARK SCHEME - UNIT SN4 (6134)A2 BIOLOGY (SNAB) January 2006

Question 1 Maximum mark

(a) Increase by 0.3 degrees per hour;

5 degree change ;

= 16.7 hours / 16 hours 40 minutes / 16 hours;(to 1 significant figure)[Full marks for just correct answer]

3 marks

(b) 1. Change / increase detected;

2. Reference to [hypothalamus / (thermo) receptors);

3. Change in activity;

4. Change in behaviour (eg find shade, cold shower);

5. Lose heat;

6. Slower generation of heat / reduced metabolic activity;

7. Temperature fall / no increase;

8. Reference negative feedback;

9. Radiate / eq;

10. Vasodilation / eq;

5 marks

Total 8 marks



(a)

1. Light harvested / eq;

2. Reference to chlorophyll;

3. Reference to [accessory / eqj pigments;

4. Electrons excited / reference to higher energy level;

5. Reference to carriers / electron acceptors / electron transport chain;

6. Reference to energy release coupled to ATP production;

7. Photophosphorylation;

8. Reference to photolysis (as electron source);5 marks

(b) Sucrose content increased;

Correct figure manipulation;2 marks

(c)

1. Less PGAL converted to RuBP / less RuBP reformed;

2. More available for [sucrose / glucose} production;

3. Enzymes for sucrose more active than for RuBP production;2 marks

(d)

1. Higher carbohydrate yield;

2. Sweeter crop / better quality crop;

3. Faster growth of crop / eq;

4. Increased profit;2 marks

Total 11 marks



(a)

1. Reference to religion;

2. Reference to creationism;

3. Description of creationism;

4. Contrary to teaching of Bible;

5. Implies man not special case (ie in God's image);

6. Description of evolution;

7. Lack of evidence for evolution / natural selection;

3 marks

(b)

1. Different alleles in different breeds / eq; [Reject gene]

2. Reference to random mating / fertilisation / eq;

3. New combinations of alleles / characteristics in offspring;

4. Reference to heterozygousity in the offspring;

2 marks;

(c)

1. Short time span / converse;

2. Chance mutations have not happened;

3. Selection pressures not enough;

4. Single case;

5. Reference to genetic isolating mechanisms;

2 marks

Total 7 marks

N25415A Page 10 January 2006 6134


(a)

1. Similar route for infection;2/3. Examples of means of transmission;;4. Immunosuppression in HIV/eq;5. Reference to opportunistic infection / eq;

2 marks

(b) T(-tell) / T-lymphocyte / T-killer;1 mark

(c)

1. Signal from surface protein;

2. Activation of PKR;

3. Reference to protein synthesis / translation / eq;

4. No production of virus;

5. Celt death / cell function disrupted;3 marks

(d)

1. PKR binds to virus protein;

2. Does not prevent protein synthesis;

3. Viruses reproduce;2 marks

(e)

1. Rapid reproduction;

2. Many (gene) mutations / relevant mutation more likely in given time;

3. Reference to variety of proteins;

4. Large variation;

5. Selection;

6. Of resistant phenotype / gene;

7. Short time;

8. Long drug development time;4 marks

Total 12 marks

N25415A Page 11 January 2006 6134


(a) (i) 1. Water loss similar (for all);

2. Appropriate ref to species;

3. Reference to comparative figures;

4. No clear correlation (between water loss and zonation);2 marks

(ii) 1. Seaweed higher on the shore recover better from drying /more tolerant of drying /converse / eq;

2. Thicker cell walls provide tolerance to drying /reject resistance to drying / converse;

3. Walls are thicker the higher up the shore / converse;

4. Thick wall aiding recovery / converse;

5. One data point does not fit / eq;3 marks

(b) 1. Callistoma on lower shore;

2. Cannot tolerate high temperature / loses water too rapidly;

3. Any other on higher shore;

4. Tolerates higher temperature /conserves water better (not obtusata);

4 marks

(c) 1. Grazing animals;

2. Predators;

3. Food (supply);

4. Parasites;

5. Competition;

6. AVP;2 marks

Total 11 marks

N25415A Page 12 January 2006 6134


(a)

1. Insects development rate / life cycle / aspect of development /rate of growth / eq;

2. Temperature dependent;

3. Rate fixed at constant temperature;

4. Reference to weather conditions affecting temperature of the room;2 marks

(b) Several values for development rate / eq;1 mark

(c)

1. Do not know temperature throughout / temperature not constant;

2. So rate rnight vary;

3. Might have died at night;

4. So infestation next morning / do not know time of infestation /entry to room difficult;

5. Too late for other evidence;

6. Other factor involved;2 marks

Total 5 marks

N25415A Page 13 January 2006 6134


(a) 1. Prevent extinction;

2. By keeping breeding populations / where natural habitat lost;

3. Breed / breeding programme to increase numbers;

4. For reintroduction to wild / reference to genetic diversity / eq;

5. Study animals / research;

6. Better understand means of conservation;

7. Education;

8. Raise awareness / support for conservation;4 marks

(b) 1. Introduce new / unrelated animals / reference to sperm bank;

2. Introduce new alleles / genes / increase gene pool;

3. Prevent inbreeding;

4. Maintain genetic diversity;

5. Stud books / pedigree records;

6. Collaboration between zoos;

7. Reference to embryo technology;2 marks

Total 6 marks

N25415A Page 14 January 2006 6134

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Order Code UA 017362 January 2006

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2006 january sn 1,4 mark scheme

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