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ANS P6 - CAMBRIDGE INTERNATIONAL EXAMINATIONS JUNE 2002 GCE...

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Unformatted text preview: CAMBRIDGE INTERNATIONAL EXAMINATIONS JUNE 2002 GCE Advanced Level MAXIMUM MARK : 5O SYLLABUSICOMPONENT :9700 I6 BIOLOGY (OPTIONS (A2)) i UNIVERSITYgf CAMBRIDGE "5 Ti"f Lucal Examinations Syndicate Mark scheme Syllabus _ A Level Examinations — June zoo: 9700 n OPTION 1 -- BIODWERSITY 1 {a} (13} ii} (iii (6) {ll {ii} A - Chordata I chordates and myotomes I segmented muscle blocks I notochord I dorsal nerve cord I post-anal tail I visceralfpharyngeal cleftsIslits ; B — Echinodermata I echinoderrns and penlamerous symmetry I tube feet Ispines ; C — Cnidaria and radial symmetry I tentacles ; 3 annelicl triploblastic, cnidarian dipioblastic ; annelid has double body openings. cnidarian single : annelid has CNS Inerve cord. cnidarian nerve net ; annelid bilaterally symmetrical, cnidarian radially ; anneiid has mesoderm. cnidarian has mesogloea; annelid segmented (cnidarian not) ; annelid has coelom {cnidarian not) ; annelid has blood vessels I pseudo heart (coidarian not) 3 max P I chaetae. for grip I anchorage ; ref retraction when moving I protmsion when stationary ; Q and R are antagonistic muscles ; Q I circular muscles create long. thin segments (contracted) ; R I longitudinal muscles create short. fat segments (contracted) ; waves of contraction (run from back to front} : muscles work against. coelom I s I coelom I 5. acts as hydrostatic skeleton ; heterotrophs I eat organic material ; in I on. soil ; eat humus I dead leaves : ref to grostomium {gripping food) ; ref to (muscular) ghaggnx (swallowing) ; 2 max earthworms. feed selectively Ido not eat all soil ; more of each element (in casts) because these are present in leaves (in higher concentration than soil) ; calcium from calcium pectate I in cell walls ; magnesium from chlorophyll ; carbon from. organic compounds (in leaves} Inamed organic compound ; earthworms may bring up leached material which has been 3 deposited in lower iayers of the soil ; max Total: 15 Hark Scheme Syllabus Paper 1 A Level Examinations — June 2002 l 9700 s 2 {a} to provide land for agriculture ; space for housing r industry ; road building ; wood for. building r fuel ; timber (for sale r export} ; mining activity ; 3 max lb} li) greater mortality at edge than at centre ; above 60 cm r larger r older. trees most affected ; uniform percentage mortality up to 60 cm : use of figures ( % + diameter) ; 2 max conditions at edge less suitable for trees ; (ii) more wind (at edge} ; larger trees more susceptible to wind damage ; lower humidity (at edge} ; more intense grazing (at edge] ; ref erosion r nutrient loss at edges ; damage from logging activities ; accept converse throughout 3 max (c) {i} fewer seedlings in smaller areas ; always most seedlings at interior (applies to both) ; less variation in 10 be than 100 be r steady decrease in 100 ha (interior to corner) ; similar number throughout 10 ha fragment and at corners of 100 ha fragment ; 2 max {ii} higher proportion of ‘edge' in smaller fragments ; so more trees killed ; especially. larger l older. ones that would be producing (most) seeds ; trees do not. flower r set seed, so easily at edges ; (so) fewer seeds produced in smaller fragments ; environment in smaller fragments. not so suitable for germination I higher rate of transpiration ; because soil is drier ; seeds more likely to be eaten before germination in smalier fragments ; 3 max (d) small fragments will have lower biodiversity than large ones ; make forest reserves as large as possible ; corridors between fragments ; 2 max Total: 15 Mark Scheme Syllabus A Level Examinations — June 2002 STUD .- 3 (a) (i} E. coii is a prokaryote. Paramecium is a eukaryote ; E has no nucleus. P has nucleus itwo nuclei ; .- E has naked DNA. P has DNA associated with histones ! true chromosomes ; E DNA is loop. P DNA linear : E has no membrane-bound organelles i named organelles. P has ; E has cell wall. P does not have cell wall ; E has smaller ribosomes than F ; E has no cilia, P has cilia ; E has pili rtimbriae. P does not; E does not have contractile vacuole. P has : E has plasmid{s), not in P ; P has food vacuoles. none in E ; P has. gullet r oral groove. not in E ; a max {ii} genetic engineering r‘gene technology : DNA from other organisms inserted into bacteria ; any example. e.g_ insulin .-' HGH! BST; Agrooacton‘um tumefaciens : used as vector! to insert genes. into plants 1 detail ; example of genes 1‘ characters used (disease resistance. resistance to herbicides} ; Lactobaciiius 1‘ Baciiius subtiiis i Serratis ; as silage inocutant ; speeds fermentation i increases nutrient content ; Acetobacter ; Vinegar production ; Converts ethanol to ethanoic i‘ acetic acid ; Bacillus thurfngiensis ; used as insecticide ; sprayed onto crops {e.g. cabbages) ; Bt toxin gene inserted into crop plants ; blue-greens i cyanobacteria .i Spiruirna ; grown for single cell protein ; ref oil spills ; eig. bacterium ; Streptococcus r Lactooacr'flus : cheese i yoghurt. production ; bacteria convert sugars to lactic acid ; therrnophillic bacteria ; as source of enzymes ; 6 max eg. proteasesi lipases r amylases. for washing powders ; Mark Scheme Syllabus Paper 1. A Level Examinations J June 2002 9700 .- [iiii Saccharomyces used for this : fermentation ; converts sugars to ethanol r alcohol ; production of gasohol l alcoholic beverages ; bread making ; ref carbon dioxide production ; antibiotic production ! named antibiotic : detail i Penicirm;_mr Streptomyces ; blue cheeses ; detail .lflavouri‘ inoculation detail ; mycoprotein ; detail 1' Fusarfum r ref non-meat protein l low fat i high fibre ; sources of enzymes ; detail ; 6 max Total: 20 (b) ti) brvophytes have no i relatively unspecialised. vascular tissue ; filicinophvtes have glam and phloem ; xylem has (vessels and} tracheids : b have rhizoids ; f (sporophyte) have true roots :' f have rhizoids only on garnetophyte ; b have thallus ; f have leaves f fronds : frond detail, e.g. rachis. pinnae; b have no true stern ; f have stem with supporting tissue ; f (often) have underground stem ! rhizome ; b have dominant gametophyte stage. f has dominant sporophyte stage ; (some) bs have no stomata. (all) f have stomata; f have sporangia in clusters! sori. on leaves. b do not ; detail sporangia structure e.g. tapetum, annulus ; b detail of sporophyte e.g. capsule with peristome ; 8 max Page 5 Mark Scheme Syllabus A Level Examinations — June 2002 9700 n (ii) poorly adapted f confined to damp environments : R dark i' shady (gametophytes) have rhizoids for anchorage to substrate ; rhizoids for absorption of, water r‘ ions ; some water transport tissues ; but not well-developed : spores are resistant to desiccation ; no Iignin I so rely on turgor for support : so cannot grow very tall : leaves {usually} one cell thick ; (most have} no cuticle ; so lose water (by evaporation) easily ; gametes require water for, fertilisation ! sperm to swim ; gametes surrounded by (sterile) cells that prevent drying out ; some have stomata that can be closed : some have waxy cuticle ; some mosses can survive long periods of desiccation f ref Sphagnum ‘wick' effect ; 6 max {iii} well adapted to life on land ; coniferophyte has vascular tissue, so water is transported to all cells r provide support; tracheids i lignified cells J woody tissue : secondary growth provides more, supporting r concluding, tissue ; so can grow large r tail ; so can intercept more light for photosynthesis ; has (true) roots so can obtain water from? deep in soil i over wide area i ref anchorage : leaf shape i‘ cuticle reduces water loss i transpiration ; bark! cork, resistant to fire ; wind pollination ; male gametes, inside pollen grains, protected r resistant to driving : fertilisation internal ! gametes do not have to swim i gametes move down pollen tube ; fertilisation not dependent on wet conditions : embryo develops in f protected in, seed ; wind dispersal : seed can lie dormant through. dry i cold, conditions ; 6 max Total: 20 Page 6 Mark SchEme Syllabus Paper A Level Examinations — June 2002 9ND IE OPTION 2 - BIOTECHNOLOGY 1 (3} lb) id} [8} involves breakdown of starch by acid hydrolysis I amylase : to sugars I named sugar : anaerobic fermentation : named organism : Saccharomms cerevisiaeI Zygomyces I Zygomonas; ' ref controlled conditions ; ref distillation : detail e.g. sterilised apparatus I batch process I aerobic initially ; 4 me: less need to extract I transport fossil fuels ; oil is finite Ibiofuels are made from renewable sources I reduces use of fossil fuels ; biofuels produce fewer harmful emissions during production : biofuels produce fewer harmful emissions during combustion : 3 max reduction in the build up of greenhouse gases ; advantages (engine performance)» good I more powerful ; (exhaust emissions} - less pollution I named example ; disadvantages — max 3 (maintenance costs) — parts costs more I need replacing more ofien; (fuel tank weight) - car heavier ; (drivability) - harder to drive ; (solvent action) - any spillage damages the paintwork more : (cold weather start} - harder to start car in colder climates ; 4 max country already produces oil ; requires a ready source of fermentable carbohydrate ; requires a cheap power supply for distillery ; not all countries have the appropriate technology ; no use in cold climates ; 2 max other fuels expensive I not available ; uses waste materials ; reduces deforestation : reduces soil erosion ; sludge left can be used as a fertiliser I increases soil fertility ; localised production ; 2 max Total: 15 Markscmme Syllabus A Level Examinations -June 2092 s'roc “ 2 (an) oxygen consumption 1 rate oxygen is used up ; pH ; H202 production it rate H202 formed : 2 max lb} (i) undernourished i stunted growth ; fatigue l fainting i come : high blood sugar levels i' glucose in urine ; excessive thirst ; eye damage : 2 ma: (ii) sugar consumption increases with time ; number of cases of diabetes increases with time ; use of figures ; increase in sugar consumption related to increase in diabetes ; 3 max (iii) not a direct relationship between sugar consumption and diabetes ; named other factor involved e.g. exercise r other dietary factors} improved diagnosis ; genetic link ; 2 max {c} injections no longer needed : reduces the long-term chance of infection ; cures the disease ; leads to a better lifestyle l less need to watch diet as carefully ; 2 max (d) cow {pig insulin differs in structure from human insulin : side effects i may cause an allergic immune system reaction in some people ; possibility of disease transmission ; genetically engineered insulin can be produced in any quantity ; cheaper to produce ; some people will not i' inject themselves with insulin from animals {for religious l personal reasons] ; human insulin quicker effect ; 4 max Total: 15 —_n:n~a_ Syllabus — A Level Examinations — June 2002 —-_ 3 (a) {it organism Fusarfum gramr'neamm; grown at 25 ~ 35°C ; . looped air flow fermenter! pressure cycle fermenter : any named nutrient requirement eg NH; r glucose l minerals sans: choline increase hyphal length ; cooling jacket l heat exchanger ; continuously harvested ; R_NA reduced : by heating to 60 - TD°C : produces mycoprotein fibres i filaments ; need to be eXtracted and purified ; cut f coloured f flavoured to produce final product ; 8 max (ii) ref fruit ripening ; better tasting fruit i vegetables ; prevents fruit softening i spoilage ; yield stability; locate important genetic traits and fast track them into breeding material; e.g. stress tolerance genes to the cold I high pH tolerance ; pest {disease control ; modification of oils! starch i protein lfibre content ; enhanced digestibility for forage animals : e.g. Canola plant producing oils for lubricants i‘ detergents ; potatoes with starches that absorb less fat on cooking : increase yield saves water in areas requin'ng irrigation ; will reduce demands on the environment 3' less space required ; crop digestibility may provide benefits in wood pulping ; 6 max (iii) enhanced iaccelerated livestock improvement programmes ; by taking advantage of genes not readily accessible ; through normal selective breeding ; e.g. enhanced disease resistance ; chickens that resist infection by Salmonella ; produce milk which contains therapeutic i medically important proteins ; to alter the milk to improve nutritional value ; achieved by inserting cooies of human genes for these proteins : and attaching them to regulatory genes ; so that the inserted gene only works in the mammary glands : leaner meat produced ; 6 max Total: 20 M—Pa per — A Level Examinations ——June 2002 9WD -_ (h) {i) increases yield ; saves water in areas requiring irrigation ; less space required ; plants genetically engineered able to for nitrogen ; external fertilisers not necessary ; excess fertiliser no longer causing pollution ; resistant to the attack of insects ; resistant to disease : prevents fruit softening i Spoilage : 6 max (ii) starter culture of bacteria ; Lactobacillus bufgan'cus. i Lactobacr‘llus acidoggir‘us ; and Stregtococcus themaghir'lus! Br'l'ido bifidum ; added to milk ; incubated at 33 - 46°C ; Lactobecillus breaks down protein ; releasing peptides : which encourage Streptococcus to grow; Streptococcus produces formic acid and 002 : which stimulate Lactobaciiius; pH reduced to 4.4 - 4+6 : Lactobacil‘ius produces lactic acid ; both organisms produce acetaldehvde ; which gives voghurt its characteristic flavour ; '7 max (iii) (inject) papain ; a protease ; into cattle immediater before! after slaughter ; enzyme circulates through tissues ; begins breakdown of fibrous proteins r' collagen i elastin ; holding connective tissue together : releases muscle fibre ; reduces storage time ; may cause an allergic reaction in some people ; public suspicious of treated meat ; T max Total: 20 Page 10 Mark Scheme Syllabus A Level ExaminatiOns — June 2002 | 9700 -_ OPTION 3 — GROWTH, DEVELOPMENT AND REPRODUCTION 1 {a} allometric ; 1 lb} {it baby' at birth has head half as big ; {or eight week fetus has head twice as big) adult has head one quarter as big : (or fetus has head four ' 2 times as big) (ii) hormones ; growth hormone I thyroxin Itestosterone ; growth of brain early ; growth of sense organs I examples Of sense organs ; ref gene switching (in different tissues] : 3 max (cl (it most birth masses around 3 kg ; fewest deaths I lowest mortality. lust above 3 kg : approx 3% modality (A 2.5 — 3.5%) ; increased mortality at lower and higher birth masses ; ref supporting figures of extreme birth masses and modality ; 3 max (ii) natural selection; favours birth masses close to 3 kg approx ; heavy and light babies more likely to die ; ref stabilising selection ; so alleles (genes) for 3 kg birth masses passed on ; 2 max id} smokers have 17' - 18% I most. babies at 3 kg ; non smokers have 18.5 — 19.5% I most. babies above 3 kg ; on average, smokers have lighter babies ; 2 max {e} lUGR I intrauterine growth retardation : carbon monoxide, diffuses across placenta Iforrns carboxyhaemoglobin I reduces oxygen to fetus ; nicotine, affects nervous system I fetal circulation I placenta '. birth complications I premature births ; resistance to infection reduced ; breathing problems I lungs immature. afterbirth ; vitamin C uptake of mother reduced 1 2 max Total: 15 2 (a) carbohydrate - sucmse from phloem I parent plant declines ; " glucose declines. as used for synthesis I respiration ; starch initial reserve ; ref to amylase ; oil - Oil synthesised from carbohydrates ; starch converted to oil ; 4 max Page 11 Mark Scheme Syllabus Paper — A Level Examinations —June 2002 (hi {0} id} (9) 3 (3) (i) 9700 low density I mass. allowing easier dispersal ; equal mass of lipid yields more energy than equal mass of calbohydrates ; ref to higher proportion of hydrogen relative to oxygen ; ref reduced microbial attack ; digestion I hydrolysis ; R breakdown ref enzymes .i lipases ; fatty acids for synthesis ; ref respiration ; detail of respiration ; dry mass would fail initially ; reserves used up : reserves respired ; ref to oil 1’ starch ; carbon dioxide released : after plumule I leaves emerged ; when photosynthesis exceeds respiration ; dry mass would increase ; breaks dormancy ; acts on aieurone layer ; amylase I hyd rolytic enzymes. activity increased ! starch digestion affected : effect on protein synthesis ! RNA synthesis ; rise during chiliing i may remove need for cold period ; ref gene switching ; acts with MA in elongation ; (2 different methods) method and appropriate plant :; part ! parts of plant involved ;; practical detail of selected technique ;; Total: 6 2 max 3 max 4 max 2 max 15 Page 12 Mark Scheme Syllabus A Level Examinations — June 2002 STUD -_ {ii} advantages only one parent needed : offspring genetically identical {clones ; known growing conditions : known time of maturity i all together : known quality .l characteristics l example ; large numbers lrapid production. (from one stock plant} ; plant diseases avoided with meristerns ; micropropagation at any time of year : (exotic) plants that are hard to produce from seed can be propagated ; cloning following genetic engineering ; 5 max for advantages disadvantages labour intensive ; problem of disease transmission ; problem of disease spread through a whole crop ; problems of harvesting at one go ; 7 max (iii) meiosis : producing pollen ; (R male gametes by meiosis) producing embryo sac ; (R female gametes by meiosis) independent assortment ; detail ; crossing-over ; detail : new allele combinations ; non-disjunction ; random fusion of gametes ; two parents involved ; ref natural selection : ref to cross-pollination ; 1' max Total: 20 3 lb) ii} secretion of thyroxin i T4 and tri—iodothyronine i T; ; iodine i iodide concentrated from blood ; thyroglobulin made istored ; hydrolysed i rel enzyme action : secretion into. blood plasma l capillaries ; thyroxin controls BMR ; ref oxygen lfood utilisation i heat generation ; cellular respiration i mitochondria stimulated ; thyroxin acts on nucleus 1' DNA I genes ; switches on RNA synthesis ; protein synthesis ; growth 1 development affected ; skeleton 1' bone : mental development ; heart rate : 8 max Page 13 Mark Scheme Syllabus Paper A. Level Examinations — June 2002 91'00 “ {ii} ref cold l season I body temperature : hypothalamus produces TFtH l TRF; TRH lTRF stimulates anterior pituitary to produce TSH ; low thyroxin causes anterior pituitary to secrete TSH ; high thyroxin inhibits TSH : action via hypothalamus ; ref negative feedback in right context : ref homeostasis : ref blood vessels from hypothalamus to ant pituitary; 6 max (iii) ref menopause symptoms '. rel hysterectomy l ovaries removed ; ovaries less sensitive to FSH ; consideration of age for HRT ; oestrogen taken in pills l implants ; osteoporosis} loss of calcium from bones ; oestrogen antagonistic to parathorrnone ; reduced risk of CHD ; ref to side effects ; example of side effects (blood clotting} ; s max Total : 20 Page“ MarkScheme Em— A Level Examinations — June 2002 9700 OPTION 4 — APPLICATIONS OF GENETICS 1 [a] li} dominant; epistasis ; 2 {ii} Inhibition {suppression ; codes for. proteinlpclypeptide ; which blocks expression of handing locus: codes for abnormal enzyme ; which cannot make band pigment ; AVP ;; 3 mm: (b) P [BBMM] x bbmm ; gametes BM 3: brn: F, Bme unbanded: Allow error carried fomard {ECFfoonsequential} marks for F1 gametes and F2 gametes BM Elm bM hm xsame: F'i.nr1.r3el‘l.I square genotypes : ; phenotypes; : yIEII-ametes unbanded unbanded unbanded unbanded m unbanded unbanded unbanded unbanded BbMM Bme beM bem unhanded unbanded midbanded midbanded midbanded five-banded ratio 12 unbanded : 3 midbanded : 1 five-banded ; a max (c) i i) genes on the same chromosome : 1 {ii} 1 unbanded pink: 1 banded yellow ; 1 Total: 15 Page 15 Mark Scheme Elm- B A Level Examinations — June 2002 WOO 2 (a) Correct ref to PCR ; cut (into fragments} ; by enzymes ; restriction enzyme 1 ...
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