9700_w02_ms_6

9700_w02_ms_6 - CAMBRIDGE INTERNATIONAL EXAMINATIONS...

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Unformatted text preview: CAMBRIDGE INTERNATIONAL EXAMINATIONS NOVEMBER 2002 GCE Advanced Level w '7' Local Examinations Syndicate E “Em UNIVERSITY of CAMBRIDGE ' Mark Scheme ’~ ' Syllabus ' — ALevelExaminations—November 2002 9700 n OPTION 1: BIODIVERSITY 1 (a) (i) (ii) (b) (i) (ii) (0) (i) (ii) Limbs support entire body weight / diameter of limbs related to the weight supported / sensible ref. to greater weight ; body weight increases proportionately with, volume of animal / cube of (linear) dimensions; allow converse throughout , dugong does not need limbs to support body weight/ body weight supported by water; dugong has streamlined shape for movement through Water; dugohg has limbs modified to form flippers; limbs l tail, with large surface area to, push against water / propel through water; . elephant has large ears, for temperature regulation Ito lose heat; (not trunk or tusks, as not'related to habitat?) Variable; no relationship between human and elephant population; below.15 humans km‘z; could be chancel elephants move around; could be influenced by availability of, water / food; elephants need areas where there are trees / not all areas have vegetation suitable for elephants; humans use land for agriculture I buildings / industry; drive away / kill, elephants who damage crops; " ' fences keep elephants out; removal of trees; some can be killed; population remains (approximately) the same; as enough animals are left to breed; over long time period; (natural) birth rate; (natural) death rate; age'at which reproduction begins; frequency with which females give birth; age structure of population; max 3 max 3 Max 2 Max 2 Max 3 Total: 15 Mark Scheme ‘ - ' Syiiabus -Pa er _ ALevel Examinations—November 2002 9700 2 (a) (i) flowers; (ii) g-petalled flowers; ignore elongated leaves parallel veins (in leaves); - (iii) adventitious; V fibrous / branching; no taproot; (iv) bundles scattered and not in a ring; 0’) half mark per correct box, round up (c) ‘ assume statement refers to angiospermophyte unless otherwise stated gametophytes / male gametes. inside pollen grain; protected from desiccation / can be dispersed over wide area; internal fertilisation / fertilisation described; not dependent on water/ male gametes do not swim; young sporophyte / embryo, develops within seed; not dependent on gametophyte / can lie dormant for long periods / can survive dry conditions; max 4 Total: 15 3 (a) " — A Level Examinations — November 2002 9700 n (i) (ii) (iii) ' “Mark Scheme ' Syllabus hyphae form mycelium; septate; septa with central pore; more than one nucleus per compartment; cell walls of chitin; and glucan; conidiophore; conidia l conidiospores; detail of conidia; sterigma l phialide; detail of cellular structure; max 6 heterotrophic; saprophytic/ saprotrophic; necrotrophic; parasitic; suitable named substrate; enzymes'secreted / extracellular digestion; named substrate and product; second named substrate and product; products I soluble substances, absorbed; diffusion / active uptake; max 6 non-cellular; no( cell) membrane / cytoplasm; nucleic acid / DNA / RNA; (may) contain enzyme / reverse transcriptase; protein coat I capsid / capsomers; ., ‘ may have, membrane / envelope, obtained from other organism; do not respire; do not take in nutrients; reproduce only inside living cell; obligate parasite; use cell machinery to copy viral DNA; description of reproduction of, RNA/ DNA viruses; some attempt to put forward an argument; max 8 Total: 20 “Mark Scheme ' ‘ - syllabus, — .‘b’ (i) (ii) (iii) A Level Examinations — November 2002 9700 -_ water has low oxygen content ; gaseous exchange surface of fish is gill lamellae; large surface area + thin (epithelium); ' detail of gill structure; blood in capillaries/ well vascularised ; ventilation provides oxygen-rich water over gills; ventilation / blood flow, maintains diffusion gradient; ventilation mechanism described; water and blood flow in opposite directions / countercurrent; speeds diffusion / increases concentration gradient; max 6 loss of water from exchange surface is problem on land; ,. locust exchange surface is tracheoles; ‘- - tracheae lined with chitin; trachebles deep inside body; spiracles can close to prevent water loss; tracheoles are, very small / thin, + large surface area; all cells are short diffusiondistance from tracheole / air; penetrate, tissues / muscles; "' withdrawal of fluid (from tip of tracheole) when muscle is active; speeds diffusion; ventilation mechanism described; max 6 exoskeleton with chitin; six jointed legs; chitin hardened except at joints / chitin more flexible at joints; detail of, leg / joint, structure; muscles attached inside skeleton; across joint; antagonistic muscles / extensor and flexor; three legs remain on ground while three move; large hind legs forjumping; leverage explained; claws for grip; ' sticky pads for adherence; max 8 Total: 20 Sv'l'ébusv _ A Level Examinations — November 2002 9700 - V “ OPTION 2: BIOTECHNOLOGY 1. (a) (b) (c) (d) (e) (i) (ii) (i) (ii) lactic acid; 002; lowers the pH / makes it more acidic; amount of microbes / yeast l bacteria / inoculum small; idea of lag'phase; ' initial drop in pH is slow due to, synthesis of enzymes / gene switching; as yeast level increases/ reaches exponential phase, pH drops quicker; levels off as, lactose is used up / too acidic; .. ref. figs. eg lag phase 1-2 h / levelling off after 6h / complete after 7-8 h; CO2 produced; by yeast; respiration; different amounts of lactose; different fat content; different protein content; other compounds / acetaldehydes/ diacetyl / alcohols produced; inoculate new cultures; food for animals; (health) food for humans; removal of microorganisms; AVP; lactose fermented; milk is starting substrate; both involve bacteria; yeast involved in fermenting kefir / only bacteria ( named bacteria) in yoghurt; different by-products formed eg alcohol; max 2 max 4 max 2 max 3 max 2 max 1 max 1 Total: 15 > Mark Scheme ‘ » Syllabus — A Level Examinations - November 2002 9700 .- 2. (a) Explant from apical dome of e.g. potato / other valid e.g.; for disease-free plants; embryos used as explant of eg. soya bean / other valid e.g.; for disease free plants; protoplast culture of e.g. tomato/ other valid 9.9.; to facilitate genetic manipulation of crop; AVP;; eg in cases of sterility max 4 (b) (i) Prevent microbial contamination; __ 7 culture media contains suitable nutrients for the growth of microbes; as microbes grow faster than plant; max 2 (ii) (shoot / root) meristems; leaf initials; young flower buds; pseudobulbs; embryonic tissue; any sensible named tissue; max 2 (c) cytokinin promotes shoot growth; higher concentrations more shoots; too much cytokinin and shoot size decrease; root development only when no cytokinin present / cytokinin inhibits root growth; reference to comparative figs; max 3 (d) Each correct answer for 1/2 mark - marks rounded up . The use must be linked to the correct ingredient. Maximum 2 for ingredients. Maximum 2 for uses. " Vitamin; correct use; N / amino acids; protein synthesis; Ca ; middle lamella formation; P; nucleic acid synthesis / ATP synthesis; Mg ; chlorophyll formation; trace elements; enzyme activators; C Source; ‘ energy source / osmoticum; S; amino acid'Synthesis; Giberellins; cell elongation; Auxin; control cell differentiation; max4 Total 15 syllabus _ A Level Examinations — November 2002 9700 r n 3. (a) (i) Primary effluent sprayed over (graded) stones lgrit lclinker; Covered in thin film of, bacterial fungi; (trickling filter system) Or passed into an aeration tank; (activated sludge process) named example of organisms involved eg Baccillus / Proteus / Pseudomonas / Zoogloea ramigera ; together with ciliate protozoa; eg Vorticella; these are aerobic; bacteria break down organic material; small solid particles digested by ciliates; Zoogloea secretes a gum; which flocculates particles together; other microbes work on the fioc. To break it down; _ all the organisms involved are sensitive to poisoning withhea’vy metals; sludge (from aerobic treatment tank & settlement tank) is broken down by anaerobic bacteria; eg Clostridium; temperature is 30—35°C; also methanogenic bacteria; eg Methanobacteria / Methanococcus / Methanobacillus / Methanosarcina / Methanospirillum; produce methane; which is used as a power source; max 8 (ii) microorganisms break down organic matter; found naturally on the substrate; initial decomposition by mesophilic microorganisms; produces heat / temperature raised; replaced by predominantly baccili; named species eg Thermus; which are thermophiles; accelerates breakdown of proteins l fats I complex carbohydrates; rise in temperature kills, many microbes l pathogens; compost temperature decreases and mesophilic microorganisms take over; . the longer the compost left the more diverse the species; Actinomycetes; degrade complex organic compounds / cellulose / lignin / chitin / proteins; appear during the thermophilic phase; fungi / moulds breakdown complex plant polymers / named example; important in mesophilic phase; enables bacterial decomposition to take place; max 6 ' ’ ' '- \Mark Scheme ' Syllabus.- — A Level Examinations — November 2002 9700 n (iii) unicellular algae; named example eg Scenedesmus; some fungi / eg mycorrhizal; acidophilic bacteria; named example eg Thiobacillus; obtains energy from oxidation; example eg ferrous iron I sulphides, to ferric iron / sulphates; aids the solubility of metals; take up metal ions from dilute solutions; named metal eg cobalt / copperl lead I zinc / uranium; accumulate ions against a concentration gradient; in non-toxic form; low gradé‘metal ores, crushed / dumped, on impermeable surface; microorganisms already present in the ore; irrigated with sulphuric acid; metal sulphate collect in lagoons; metal extracted by, physical / chemical methods; water/ acid solutions recycled; max 6 Total: 20 Page 9 f: . Mark Scheme - i ' syllabus _Pa er — A Level Examinations - November 2002 9700 i 3. (b) (i) Monoclonal antibodies— maximum 4 group of identical antibody molecules; recognise only one type of antigen; produced from hybridoma cells; formed from fusion of B-lymphocytes; and myeloma / tumor cells; ' hybridoma cells have culture immortality; Biosensor — maximum 4 device for measuring chemical compounds /molecules; have immobilised enzyme; transducer; amplifier; , enzymes; recognise & select only one type of molecule lspecific; used to detect molecules at low concentrations; max 6 (ii) used to identify different strains of pathogens; eg hepatitis B; detection of, virus particles l microbial toxins ; in infected blood / tissues; cancer diagnosis; detection of tumour antigens; prior to development of symptoms; detail; therapy; carriage of cytotoxic drugs directly to tumour cells / magic bullets; detail; purification of interferon; affinity ligands to bind / purify compounds; preparation of vaccines; identification of immunogenic parts of, viruses / bacteria; for use as subunit vaccines; passive immunization; - named example eg malarial rabies linfluenza; for immunologically compromised hosts; eg due to, NUS / radiotherapy / drugs; max 8 (iii) immobilised enzyme is glucose oxidase; in protectiveggel / matrix; made of cellophane acetate; ‘ detect low levels of glucose; from a sample of blood; glucose is oxidised; to gluconic acid; and hydrogen peroxide; reaction causes changes; in a transducer; produces a current; platinum electrode; current directly relates to amount of glucose; max 6 Total: 20 Page 10 'ri‘Mark Scheme ' ' syllabus —Pa er _ A Level Examinations — November 2002 9700 OPTION 3: GROWTH, DEVELOPMENT AND REPRODUCTION 1 (a) (i) (ii) (iii) 0?) (c) (i) (ii) (iii) (iv) Fertilisation birth. must get both right for one mark; 1 18% adult 82% fetal; i A rapid growth / associated with placental need to get oxygen (from mother); No nucleus; Different Hb; Biconcave shape; max 2 SLshaped curve / sigmoid; (very) high affinity for oxygen; small increase in p02 causes large increase in oxygen carried; , oxygen released to tissues (at lower p02); ' (steep part of curve) rapid release, with small decrease p02; suitable comparative figs; (in relation to fetgl curve) allosteric binding described; max 4 fetal steeper than maternal; fetal shifted left; fetal (remains) saturated at lower p02 / higher maximum saturation; fetal carries more 02., at any given p02; comparative figs % and KPa for both; max 3 maternal haemoglobin must release oxygen at a particular p02, while fetal haemoglobin picks up oxygen / fetal haemoglobin has higher affinity; to allow 02 transfer (from mothers blood) to fetal blood; fetal haemoglobin has different polypeptide chains; max 2 blood system of embryo poorly developed; embryonic haemoglobin holds oxygen at a low p02;.. .. ' 1 AVP; Total: 1 5 Page 11 Syllabus — A Level Examinations - November 2002 9700 n (a) garden pea french bean hypogeal " epigeal; epicotyl elongates hypocotyl elongates; cotyledons below soil cotyledons above soil; testa stays below soil * testa moves above soil; _ (A) no lateral roots many lateral roots present; __ Max 3 (b) (i) heat to constant mass; at 110°C or less; cool in a desiccator; ' , I weigh; h Max 3 (ii) nitrate r mean yield less, (than control] A) may not be significant; standard deviation greater; ref figs; ( must include units) phosphate - mean yield greater, (than control IA) standard deviation greater; ref figs; (must include units) y ref to significance of results; max 4 (iii) nitrate - soil might have sufficient nitrogen; beans (are leguminous) can fix nitrogen; via bacteria in nodules; phosphate - phosphate increases, growth , of beans; - sincesoil might be deficient; used for, ATP I used for hexose phosphates I phospholipids; used for, DNA I RNA; _ max 5 Total: 1 5 —Page 12 I. m — A Level Examinations — November 2002 9700 (a) (i) (ii) unspecialised cells I totipotent cells; DNA replication; during interphase; mitosis; cytokinesis; exact replication of genetic material; all cells form a clone; organelles replicate; ref mitochondria / chloroplasts; cells enlarge / elongate; ref vacuolation; ref cell wall; cells specialise / differentiate; different genes are switched on; example of specialised cells; Destrogen Follicular phase; Shedding of lining / endometrium (day 1 to 5); Myometrium excitable / muscles sensitve to hormones; repair; endometrium, supplied with (straight) arteries / vascularised; endometrium becomes glandular; -. up to,'ovulation / day 14; progesterone secretory phase; endometrium thickened; ref coiled arteries; ref coiled glands; venous blood lakes / sinuses; change in the cervical mucus; secretion from uterine glands; myometrium less excitable; maintains endometrium; from ovulation I day 14 to day 28; ; reduction of steroid I progesterone induces menstruation; n max 8 max 6 max 6 Total: 20 Page 13 'I Illllark Scheme ‘ ' Syllabus V. — A Level Examinations — November 2002 9700 n (b) (i) PFR acts as inhibitor; ref. to photoperiod; (critical) dark period needed; that is continuous; to allow phytochrome to be converted; also far red light; PFR a PR2 so inhibition removed; leaves act as receptors; ref to florige'n / gibberellic acid; transmission via phloem; switching of genes; in shoot apex Imeristem; specialisation of cells; to form anthers I carpels / other named parts; example given; ' max 8 (ii) Gibberellin I GA, stimulates germination / breaks dormancy; in light requiring seeds; ~ in seeds that need chilling; cytokinins promote germination; cytokinins and gibberellins may work (alone or) together; ethene promotes germination; ethene may work with, cytokinins / gibberellins; ABA/ abscisic acid, inhibits germination / causes dormancy; ref to leaching of ABA; ABA antagonistic to, cytokinins l gibberellins; ABA levels decline with chilling; idea of different seeds responding differently; ref to mechanism of ABA action; ref to mechanism of gibberellic action; ref gene switching; max 7 IAA I NAA/ auxin promote fruiting; in pears / strawberries / tomatoes I grapes I other named (iii) example; ref parthenocarpy; fruit no seeds; maturation ethene promotes ripening; . in bananas / other named fruit; idea of putting ripe fruit with unripe fruit to promote ripening; ref fruit drop; , lack of pollinators; max 5 Total: 20 Pagan syi‘iébus per _ A Level Examinations —- November 2002 9700 .- OPTION 4: APPLICATIONS OF GENETICS 1 (a) Via/environment; , VG/genotype; 1 2 (b) (i) selection for particular trait(s); of benefit to man; artificial selection; choosing which individuals may breed; assuming trait heritable; ongoing selection/ref. time number of generations; . - max 3 (ii) small number breeding individuals; may not have all alleles; loss Of alleles linked to discarded traits; inbreeding / backcrossing; = many generations; increases homozygosity [decreases heterozygosity; max 3 (c) seeds, from many sources lfrom many phenotypes; dehydrated; chilled / frozen; ref. effect on storage life; (doubled for reduction of 5°C or 2% humidity) labelled / packaged; sample germinated, at intervals/every 5 years; seed from these plants returned to bank; max 4 (d) (i) Yes, diversity reduced; ref. %; but only one gene considered; max 2 (ii) greater selection for regulatory region; differences may alter gene switching; difference between species is, amount of product/whether gene switched on; . ‘ - switching on more important than differences in product; max 1 Total: 15 2 (a) (i) '_ chance / random; " 'rnthation'; of, chromoneme / plasmid -/ DNA; m a x 2 (ii) Natural selection; Antibiotic = selective agent; Vertical transmission; - Horizontal transmission; Conjugation / transformation / transduction / description of process; max 3 (b) (i) Sample sites not free from contact with antibiotic; Allele / gene / mutation giving resistance to one gives resistance to other; Small / common / easily achieved, mutation; on plasmid so easily transferred; A.V.P.; I max 3 Page 15 Syllabus — A Level Examinations — November 2002 9700 .- (ii) not closely related to other species; less horizontal transmission; more easily killed by antibiotic; different enzymes/pathways; ' A-V-P.'. ; ‘ max 2 (iii) affects, crucial pathway / pathway with no alternatives; requires large mutation; requires series of mutations; A.V.P.; ; V _ max 2 (c) not supported; except in case of antibiotic B; _ v bacteria supposedly not in contact with antibiotic show resistance; up to 100% of colonies tested; . . max 3 > Total: 15 3 (a) (i) female superovulated; ref. FSH I brand name; either fertilised; or oocytes harvested; embryos flushed from uterus; iVF; embryos genetically tested; embryos sexed; embryos, subdivided/cloned; embryos implanted into surrogates; treated with hormones to, prepare uteruses / synchronise cycles; surrogate may not be same species; surrogate may be temporary portmanteau; max 7 (ii) explant; sample, meristematic / totipotent/ cambium. cells; surface sterilised/treated with hypochlorite/treated with bleach; placed in sterile medium; with nutrients / named nutrients; hormones / p-g-s. to- promote division; mitosis / cytokinin; forms callus; callus subdivided; placed in medium with, hormones l p-g—s, to promote differentiation; auxin / gibberellin; I _ plantlets; . . hardening medium / sterile. sand / soil; max 7 (iii) Embryo transplantation Increases number of offspring from desirable female; does not put female at risk from pregnancy; subdivision / cloning, further increases number of desirable offspring; gives. herd/flock/etc., with desired trait quickly; plant tissue culture » all plantlets from a callus genetically identical; multiplies desirable hybrid which will not, breed true / breed; multiplies particular genotype for subsequent crossing; so speeds up selective breeding; max 6 Total: 20 g Page 16 — (b) (i) ‘ Mark Scheme - I HIE—Pa er A Level Examinations - November 2002 9700 trisomy 21; non-disjunction; usual origin / 95%, of Down’s; in, meiosis; l/production of secondary oocyte; chancel not inherited; usually maternal; increased chance with increased maternal age; can be paternal; also increased chance with increased paternal age; translocation; end of long arm of 21 onto other chromosome; rest of chromosome 21 lost; carrier has 45 chromosomes; this type Down’s can be inherited; max 7 amniocentests. chorionic villus sampling DNA profile, N __________ “Mucwmcwgfitmw ................................... ,, tests fetus; tests fetus; tests, possible carrier parent/embryo; sample amniotic fluid; sample chorionic villi of sample, blood I skin / hairl placenta; cell from IVE embryo / cell _ from amio or CVS; 13 —16 weeks pregnancy; 9 - 12 weeks pregnancy; results 2 - 3 weeks later; results quicker than amnio; results in hours; cells cultured to divide; cells cultured to divide; DNA fragmented with restriction enzymes; exploded by putting into (rest as amniocentesis) electrophoresis; water: karyotyged; radioactive geneprobe/ altered pattern of bands; chromosomes. counted l Autoradiography/ examined for UN. light; translocatlons etc.; - fluorescent. chromosome marker I came probe: Mark from one technique or from more than one. max 7 give information about. severity of disorder I quality of life with disorder; _ and treatment available; Componentsof diet to be avoided; time of onset; explain probability of risk of passing on condition; explain options available; in light, of religion / culture / ethics; put individuals in position to make own choice; max 6 Total: 20 ...
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This note was uploaded on 01/25/2012 for the course BIO alevels taught by Professor J.b during the Spring '11 term at Taylor's.

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9700_w02_ms_6 - CAMBRIDGE INTERNATIONAL EXAMINATIONS...

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