Answer guide for O Level Biology (5090/2) – Paper 2 Theory November 2000
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efficient / favourable / best / optimum (temperature) / body temperature ; 2 (for) enzyme(s) (or either named) ; Hole 1: no enzyme / protease / no effect on milk / not digested / not broken down / control ; Hole 2: lactose / sugar not responsible for the colour ; Hole 3: milk protein (or named) digested OR protein responsible for the colour of milk / amino acids colourless ; Hole 4: enzyme destroyed / denatured / inactivated / control ; Hole 5: enzyme / protease (present) / (milk) protein digested / hydrolysed / broken down ; 5 meat, or meat implied, contains protein ; enzyme / protease tenderising / partially digesting (meat / protein) ; 2 osmosis / diffusion ; 1 Direction: to the left / toward potato cylinder / arrow shown pointing 1 to the left ; Explanation: lower water potential / relatively fewer H2O molecules + in potato cylinder ; water enters potato (cylinder) ; carrying / pulling water / air bubble along capillary tube ; [max 1] 1 concentration / water potential + cell sap / cells / tissues / potato ; equal to that of the solution / isotonic ; no movement of water ; [max 2] 2 water leaves the potato / cells / tissues / exosmosis ; cylinder decreases in width / length / loses turgidity / becomes flaccid / falls into solution ; 2
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Answer guide for O Level Biology (5090/2) – Paper 2 Theory November 2000
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any three from: broad / wide, major vein / midrib, net / branched venation , petiole / 2 leafstal ;; drawing to show clearly the following : longer than broad and without obvious petiole ; parallel veins (more than one) ; 2 any 4 from: dicotyledonous plants 2 cotyledons / seed leaves, tap / main / central / primary root, flower parts in 4s / 5s, different / distinct sepals and petals, cambium, vascular bundles in stem in a circle, xylem central / few groups in root ,
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monocotyledonous plants 1 cotyledon / seed leaf, fibrous or described root, flower parts arranged in 3s, sepals and petals not distinct / different, no cambium, vascular bundles scattered in stem, xylem in many groups / pith central in root,
;;;; importance must be correct for named plant (importance) up to 2 named nutritional constituents (e.g. starch, protein, vitamins, minerals) or 1 constituent and its function (e.g. fat ; for energy ; ) ;; part of plant which is used (e.g. stem / root / seed) ; name of food (e.g. bread) / easy to grow / high yield / grows well / cheap ; [max 3]
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glucose ; fright (or any other acceptable emotional event) ; adrenaline / epinephrine more / increased / released ; glycogen (to glucose) / inhibition of insulin ; reference to energy and muscles ; max Blood sugar: (sugar) used in respiration ; (re)converted / changed to glycogen ; reference to insulin ; [max 2] Adrenaline: (adrenaline) broken down and liver ; passed out in urine / reference kidney ;
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Answer guide for O Level Biology (5090/2) – Paper 2 Theory November 2000
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U ciliary muscle , V cornea , W iris , X sclera / sclerotic (coat), 4 x 1/2;; 2 refraction shown at cornea / at or through lens, both lines must bend inwards ; rays meeting on fovea ; 2 1 A/B; ciliary muscles ; contract ; (suspensory) ligaments ; slacken / loosen ; reference to elasticity of lens ; [max 4] 4 low light intensities / dawn / dusk / dim light ; photosynthesis ; respiration ; at same rate / balance / compensation point ; oxygen uptake = oxygen evolution ; carbon dioxide uptake = carbon dioxide evolution ; [max 4] xylem ; in vein / vascular bundle ; to palisade / spongy / mesophyll (cells) ; water film ; evaporation ; air / intercellular spaces ; diffusion ; [max 6] (more) stomata (on lower surface) ; cuticle (on upper surface) waterproof / waxy ;
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Answer guide for O Level Biology (5090/2) – Paper 2 Theory November 2000
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biceps + triceps (for elbow or appropriately for other named hinge joint) ; correct ref. attachment to radius / ulna or as appropriate ; one muscle contracts while the other relaxes ; muscles can only pull / contract / work only when contracting / cannot push ; antagonistic / correct reference to flexor and extensor / biceps for bending and triceps for straightening the arm ; tendons join muscle to bone / for transmission of force to bone ; 5 [max 5] Vitamin D / vitamin C if reference to osteoporosis ; dairy produce / eggs / liver / margarine / fish ; calcium ; dairy produce / milk / water / nuts / grains / fruit / green vegetables ; fluoride / fluorine / protein ; [max 4] 4 weak / soft bones ; deformed legs / arms / bones ; teeth rot / decay / thin enamel / caries ; 3 transpiration / evaporation from plants ; evaporation from soil / lakes / rivers / seas / bodies of water ; cloud formation ; condensation / precipitation / rain / snow etc. ; water evolved from breathing out / respiration / combustion ; sweating / urination / perspiration / excretion ; water used in photosynthesis ; [max 5] 5 decrease in transpiration / water uptake ; effect on cloud formation / less rain ; desertification / hotter / drought ; less used for photosynthesis ; [max 3] 3 (no roots) to hold soil / loss of soil stability ; no canopy to protect soil / greater drainage into rivers / lakes / seas ; erosion by water / wind ; lack of humus ; lack of fertility / salts / poor water-retention ; greater temperature fluctuations ; [max 4] 4
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Answer guide for O Level Biology (5090/2) – Paper 2 Theory November 2000
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softened / melted / bolus formation / chewing / mechanical or physical digestion ; bile ; alkaline / neutralises ; emulsification / increased surface area ; reference to faster enzyme action / digestion ; lipase ; from pancreas / pancreatic juice ; from duodenum walls / in intestinal juice / released by duodenum ; fatty acids + glycerol ; insoluble / large or complex molecules / non-diffusible + converted to soluble small or simple molecules / diffusible ; villi ; Lacteal / lymph (capillary) ; absorption ; [max 10] 10 insulation / in cell membranes / as shock absorber ; energy (store) ; storage / solvent for vitamins ; [max 2] 2 (continuous) wide range / example / graph showing a normal distribution ; caused by genes / alleles / chromosomes / DNA / inheritance ; and environment ; (discontinuous) only few possible variants / example / bar chart ; no intermediates ; caused only by genes ; [max 5] reference to advantage / adaptation and changing environment ; natural selection ; survival (of the fittest) ; to reproduce / breed / hand on genes ; leads to evolution ; [max 4] change in chromosomes , Down’s syndrome ; one extra / 47 ; change in gene / allele , sickle-cell anaemia; structural alteration either of gene or haemoglobin ; [max 3]
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