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Oxford Cambridge and RSA Examinations

GCE

Biology Advanced Subsidiary GCE

Unit F212: Molecules, Biodiversity, Food and Health

Mark Scheme for January 2011

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This mark scheme is published as an aid to teachers and students, to indicate the requirementsof the examination. It shows the basis on which marks were awarded by Examiners. It does notindicate the details of the discussions which took place at an Examiners meeting before markingcommenced.

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candidates scripts must be given marks that fairly reflect the relevant knowledge and skillsdemonstrated.

Mark schemes should be read in conjunction with the published question papers and the Reporton the Examination.

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OCR 2011

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F212 Mark Scheme

Question Expected Answer Mark Addit ion1 (a) (i) human immunodeficiency virus / HIV ;

1DO NOT CREDIT if

1 (a) (ii)1

2

3

(infective agent), in blood / body fluids ;

idea of: used needles are contaminated ; ora

reduces chance of sharing needles ; ora2 max

1 ACCEPT any infec

question asks for mo2 ACCEPT e.g. used2 ACCEPT e.g. new2 DO NOT CREDIT

3 IGNORE prevents

1 (b) (i)

amino acid(s) ;

nucleotide(s) ;

2

Answers must be on co ACCEPT phonetic sp

DO NOT CREDIT if

ACCEPT ribonucleo

1 (b) (ii)1

2

3

4

reverse transcriptase in (host) nucleus ;

viral DNA, (inserted) in (host), chromosome / DNA ;

idea of: (viral) RNA / mRNA produced / transcribed ;

(to) code for / make / translate, viral proteins ;2 max

4 IGNORE different

1

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F212 Mark Scheme

Question Expected Answer Mark Addit ion1 (c) (i)

1

2

3

4

5

6

7

8

9

not vaccinated against TB ;

weakened immune system ;

(lifestyle) e.g. poor diet / lack of protein / malnourished /smoking / alcoholism ;

homelessness ;

poor ventilation (of housing) / AW ;

overcrowding ;

close contact with people from / visiting, area where TB iscommon ;

close / prolonged, contact with individual(s) with TB ;

consumption of milk or beef, from infected cattle / indeveloping countries ;

3 max

Mark the first three awhich l ine they are on1 IGNORE general re

3 DO NOT CREDITIGNORE poor health

7 ACCEPT area wherquarantined

2

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F212 Mark Scheme

Question Expected Answer Mark Addit ion(c) (ii)

1

2

3

4

5

cytokine / interleukin / receptor has, specific / unique,

shape ;

(cytokine / interleukin), binds / attaches / bonds to / fits into,receptor ;

receptor on (cell surface) membrane (of B lymphocyte) ;

(receptor and cytokine have) complementary shapes ;

activates / stimulates, clonal expansion / mitosis ; 3 max

1 DO NOT CREDITthis is implied in questi

3 DO NOT CREDIT

5 ACCEPT activates

Total 13

3

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F212 Mark Scheme

Question Expected Answer Mark Addit ion2 (a) (i) blue-black / black / dark blue ;

1

ACCEPT dark purpleDO NOT CREDIT bdarkness

ACCEPT acceptable c

2 (a) (ii)

1

2

between oxygen and hydrogen (atoms) ;

(between) electronegative / -, and electropositive / + ;

2

CREDIT marking poinmax 1 if incorrect cha

1 DO NOT CREDIT

2 DO NOT CREDIT2 ACCEPT slight / pa

2 (a) (iii )1

2

3

hydrogen / H, bonds break ;

helix, lost / unravels / AW ;

iodine, released / no longer in complex / AW ;2 max

IGNORE refs to dena

2 ACCEPT spiral / co

3 ACCEPT no longer

4

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F212 Mark Scheme

Question Expected Answer Mark Addit iontake samples at a range of times / AW ;

same volumes (of solutions) added / removed (each time) ;

heat with, Benedicts (solution) / CuSO 4 and NaOH ;

(use of ) excess Benedicts ; changes to, green / yellow / orange / brown / (brick) red ;

remove precipitate / obtain filtrate ;

colorimeter ;

calibrate / zero, using, a blank / water / (unreacted)Benedicts ;

use (red / orange) filter ;

reading of, transmission / absorbanceORmass of precipitate ;

more transmission / less absorbance, of filtrate,OR greater mass ppt, = more maltose present ; ora

using, standard / known, concentrations (of maltose) ;(obtain) calibration curve ; plot, transmission / absorbance / mass of ppt, against

(reducing sugar) concentration ;use graph to read off concentration of maltose / AW ; 6 max

B2 must be in context reaction mixtureB3 DO NOT CREDITB3 DO NOT CREDIT

mixture at the begin

C6 CREDIT descriptie.g. filtering / ce

8 IGNORE control

9 DO NOT CREDIT

T10 ACCEPT measunot, pass through

11 if unfiltered Benedindicated as being prtransmission / more abpresent11 DO NOT CREDITcolorimeter12 CREDIT serial di

2 (b) 1

B2

B3

B4B5

C6

C7

8

9

T10

11

121314

15 QWC correct sequence ; 1 1 of mps B2 to B5 ,

5

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F212 Mark Scheme

Question Expected Answer Mark Addit ion2 (c) (i)

12

3

increases / greater / faster ;reaction completed in / plateaus after / concentration is

100% after, 3.5 minutes ;figures with units to support mp 1 ;

2 max

1 ACCEPT any time

3 two maltose concentrgiven time or two timesmaltose concentration.3 ACCEPT calculated3 DO NOT CREDIT3 ACCEPT any concewithin 0.05 min.

The percentage concentration of maltose (%) presPresence or absence of chloride ions

0.0

min

0.5

min

1.0

min

1.5

min

2.0

min

Chloride ions present 0 24 54 70 80 8

Chloride ions absent 0 12 20 29 36 4

Difference in maltose concentrationWhen chloride ions are either present

or absent0 12 34 41 44 4

Allow a + /- 1% for any concentration of maltose and a +/- 2% for the difference in

2 (c) (ii) 1

2

3

(acts as a) cofactor ;

(Cl -) binds to, enzyme / amylase / amylose / substrate ;

enzyme substrate complex / ESC, forms more, easily /quickly ;

2 max

1 IGNORE coenzym

2 ACCEPT binds to,

3 ACCEPT descriptio

6

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F212 Mark Scheme

Question Expected Answer Mark Addit ion2 (c) (iii)

1

2

3

4

5

6

temperature ;

pH ;

enzyme / amylase / chloride, concentration ;

substrate / starch / amylose, concentration ;

constant / regular, stirring ;

(fixed) volume of solution

(removed each time for sampling) ; 3 max

Mark the first three awhich l ine they are onDO NOT CREDIT re

3 IGNORE amount 3 DO NOT CREDIT

4 IGNORE amount 4 DO NOT CREDIT

Total 19

7

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F212 Mark Scheme

Question Expected Answer Mark Addit ion3 (a) (i)

1

2

3

4

(all), sub-arctic / all 4 named sub-arctic, species / birds,show decrease ;

(all / most), other / non sub-arctic / all 4 named non sub-arctic, species / birds, show, increase / no change ;

greater change / AW (in breeding success), in sub-arctic

than in non sub-arctic species ; comparative figs (in 1970 AND 2000) ;

3

ACCEPT reference tosuccess throughout1 sub-arctic species = s+ ptarmigan + dotterel

2 non sub-arctic speciemeadow pipit + ring ou

4 number of young for sub-arctic species in 19subtraction between the4 DO NOT CREDIT

2000

number of young raised per yearspecies

1970 2000 difference in number of youngraised between 1970 and 2000Snow bunting* 78 2 Down 76

Lapland bunting* 7 0 Down 7

Ptarmigan* 1280 876 Down 404

Red g rouse 890 962 Up 72Wheatear 209 231 Up 22

Meadow pipit 23 82 Up 59

Ring ouzel 23 26 Up 3

Dotterel* 45 35 Down 10

8

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F212 Mark Scheme

Question Expected Answer Mark Addit ion3 (a) (ii)

1

2

3

4

5

climate change / global warming ;

(environmental) change too rapid for adaptation ;

change in, flora / plants / food supply / insects / prey /predators / human activity ;

disease (that affects sub-arctic species more than others) ;

sub-arctic species, less well-adapted than / have beenoutcompeted by, non sub-arctic species / AW ;

2 max

1 IGNORE greenhous1 DO NOT CREDITenough without referen

3 ACCEPT camouflareduction in size of hab

5 ACCEPT ora

3 (b) (i) the number of species present (in a habitat) ;

1

DO NOT CREDIT ra

9

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F212 Mark Scheme

Question Expected Answer Mark Addit ion3 (b) (ii)

1

2

3

4

5

6

idea of: unbiased method to selecting sampling area ;

sample many times / AW, and calculate mean / average ;

standardised sweeping procedure ;

ensure insects do not escape (before being identified) ;

method to prevent recounting ;

sample at different times of, day / month / year / weatherconditions ;

3 max

Mark the firs t three s1 ACCEPT e.g. randocoordinates OR use of t1 IGNORE random s

3 e.g. same type of mosame number of sweep3 ACCEPT sample at3 IGNORE same colle3 IGNORE refs to usitechniques in order to c

4 ACCEPT use of po

5 if ref to mark-releaseand recapture and lookrecounting

10

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F212 Mark Scheme

Question Expected Answer Mark Addit ion4 (a) 1

2

3

4

free from, disease / illness ;

physical and mental and social wellbeing / AW ;

good nutrition ;

suitably housed ; 2 max

1 ALLOW infectiondisease

2 DO NOT CREDIT

3 ACCEPT balanced

4 ACCEPT ref to eco

12

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F212 Mark Scheme

Question Expected Answer Mark Addit ion4 (c) (i)

1

2

3

4

5

lives, on / in / in contact with, and harms host ;

takes nutrition from / feeds on (host) ;

warmth ;

protection / safe place / AW ;

allows transmission / spread, to a new host / AW ;

4 max

1 living on / in must befeeding1 IGNORE live off

3 ACCEPT incubate

5 ACCEPT distributehost

4 (c) (ii) 1

2

3

wash / clean / disinfect / sterilize, hands ;

not, scratching / touching, of anus ;

drugs to, kill / remove, parasite / eggs ;

2 max

2 ACCEPT method tonails2 IGNORE wash anu

3 DO NOT CREDIT3 IGNORE anti-bact

Total 12

14

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F212 Mark Scheme

Question Expected Answer Mark Addit io5 (a)

statement

DNA only ( D)or

RNA only ( R)orboth DNA and RNA ( B)

contains thymine D

contains ribose R ;

consists of 2 chainsconnected to each other

with hydrogen bonds

D ;

has a sugar-phosphatebackbone B ;

has 4 different nitrogenousbases B ;

contains a pentose sugar B ;

is found in the nucleus andcytoplasm R ;

6

Award 1 mark for eaDO NOT CREDIT i

15

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F212 Mark Scheme

Question Expected Answer Mark Addit ion5 (d) (i)

1

2

no DNA from living specimens in Wales analysed ;

population (may have) evolved / mutations have occurred /genetic variation, (since 1948) ;

1 max

2 ACCEPT descriptio2 DO NOT CREDITof pine marten populati

5 (d) (ii)

1

2

3

4

5

(introduced) pine martens might not be adapted to localconditions / AW ;

(local) habitat, might have changed / is no longer suitable(for any pine martens) / AW ;

introduced, pine martens, might outcompete native,population / pine martens ; introduced pine martens might bring disease ;

Welsh pine marten would lose its, distinctiveness / identity,because of interbreeding ;

1 max

ACCEPT animals as Aanswer 1 ACCEPT not adapt1 DO NOT CREDIT

3 ACCEPT introduceWelsh pine martens3 IGNORE compete

Total 14

17

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F212 Mark Scheme

Question Expected Answer Mark Addit ion6 (a) (i)

genes / genetic / mutation ;

environment(al) ; 2

Mark the first answerIGNORE inherited / D

6 (a) (ii)1

2

3

4

no defined categories ;

range of values / intermediate values ;

influenced by, environment / many genes / genes andenvironment ;

quantitative / has to be measured / cannot be counted ; 3 max

2 ACCEPT ref to belldistribution 3 ACCEPT any ref to

4 ACCEPT metric

6 (a) (iii ) B ; 1

DO NOT CREDIT if

6 (a) (iv)1

2

3

4

growth too rapid ;

increased susceptibility to, disease / named abnormality ;

inbreeding ;

reduces gene pool / genetic variation / genetic diversity ; 2 max

2 e.g. bone / skeletal ab

3 DO NOT CREDITmutations

4 IGNORE refs to bio

18

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F212 Mark Scheme

Question Expected Answer Mark Addit ion6 (a) (v)

1

2

3

4

5

6

maintain biodiversity ;

aesthetic (reasons) / tourism ;

ethical (reasons) ;

part of a food chain / web ;

maintain / increase gene pool ;

genetic resource / availability to breed with domesticchickens ;

2 max

3 ACCEPT religious

4 ACCEPT food sour

6 CREDIT descriptionor source of genetic va6 ACCEPT specific ee.g. disease resistance /

heat tolerance / idea of

19

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F212 Mark Scheme

Question Expected Answer Mark Addit ion6 (b) (i)

1

2

3

4

5

reduces / prevents (infectious) disease ;

prevent, problems / named problem, with gut ;

digest food more, efficiently / easily / quickly ;

greater proportion of, food / energy,can contribute to growth ;

reduce risk of transmitting, pathogens / named pathogen, tohumans ;

2 max

Mark the firs t two an1 IGNORE illness

2 e.g. diarrhoea

4 ACCEPT faster grogrowth4 IGNORE larger chic

5 ACCEPT meat lesbacteria

6 (b) (ii)

1

2

3

(antibiotic) resistant, pathogens / bacteria ;

antibiotics kill useful, bacteria ;

idea of: antibiotic passing into human food ;1 max

1 ACCEPT microorg1 IGNORE germs1 DO NOT CREDIT

2 DO NOT CREDIT

Total 13

20

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F212 Mark Scheme

Question Expected Answer Mark Addit ion

sequence / chain, of amino acids ; (amino acids) joined by peptide bonds ;

secondaryalpha / , helix ;small regions of, beta / , pleated sheet / fold ; hydrogen / H, bonds ;

tertiarysecondary structure / helix / polypeptide chain, undergoes

further, coiling / folding ;

3 bonds / interactions from: disulfide / ionic / hydrogen /

hydrophobic or hydrophilic ;

hydrophilic R groups on outside (of molecule) / hydrophobicR groups on inside (of molecule) ;

quaternary4, polypeptides / subunits ;

2, alpha / , chains and 2, beta / , chains ;

1 haem (group) per polypeptide / 4 haems (per molecule) ;

prosthetic group (is) haem, (which) contains Fe 2+ ;

6 max

CREDIT marking poindiagram 1 IGNORE polypepti

S3 Must be in context

T1 ACCEPT polypep

T2 IGNORE if clearly

quaternary structuresT2 H bond must be in

contains 2 and 2Q2)Q3 IGNORE protein polypeptide

3 ACCEPT iron ion /3 DO NOT CREDIT

7 (a)

12

S1S2S3

T1

T2

T3

Q1

Q2

Q3

3

QWC - correct refs to secondary, tertiary and quaternarystructure ; 1 1 S mark and 1 T m

21

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F212 Mark Scheme

22

Question Expected Answer Mark Addit ion7 (b)

1

2

3

4

5

6

(collagen has)amino acid, chain / sequence ;

peptide bonds ;

helical / helix ;

3 bonds / interactions from: disulfide / ionic / hydrogen /hydrophobic or hydrophilic ;

quaternary structure ;

more than one polypeptide / subunit ;4 max

Assume answer refers tIf the answer mentions candidate thinks any fehaemoglobin.

1 IGNORE polypepti1 IGNORE repeating

3 DO NOT CREDIThaving an helix

5 IGNORE primary /s

6 ACCEPT polypeptipolypeptides if numberTotal 11

Question Expected Answer Mark Addit ion8 1

2

3

4

5

6

antibodies ;

natural ;

artificial ;

natural ;

antigen ;

vaccination ; 6

ACCEPT minor mis-sbe confused with anoth

Total 6

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