CCHY 2017 Bio Yearly TYS ANS

6093 Biology Yearly TYS 2017 No Paper 1 Marks Remarks 1 C 1 2 A 1 3 A 1 4 D 1 5 B 1 6 D 1 7 C 1 8 B 1 9 B 1 10 C 1 11 A 1 12 A 1 13 C 1 14 B 1 15 C 1 16 A 1 17 C 1 18 B 1 19 A 1 20 A 1 21 D 1 22 D 1 23 B 1 24 C 1 25 A 1 26 A 1 27 B 1 28 A 1 29 B 1 30 D 1 31 B 1 32 C 1 33 A 1 34 C 1 35 C 1 36 A 1 37 C 1 38 D 1 39 A 1 40 B 1 Total 40

Paper 2 Section A Marks Remarks 1a Homeostasis is the maintenance of a constant internal environment and conditions within the body of an organism + consisting of blood and tissue fluid; Receptors detect stimuli + negative feedback system + reacts to give a reverse effect of a stimulus + restoring the normal condition of the internal environment; 1 1 Definition Describe negative feedback 1b Ductless glands that secrete hormones directly into the blood + transported in the bloodstream to a target organ; e.g. pituitary gland secretes ADH to regulate reabsorption of water at the walls of collecting duct/ adrenal gland secretes adrenaline to increase metabolic rate/ pancreas secretes insulin and glucagon to regulate the BGC 1 1 Definition Example 1ci A: glycogen B: glucagon 1 1 1cii Muscular contractions + increase rate of aerobic respiration + increase demand of glucose; increase glucose uptake into muscle cells + lowering BGC; 1 1 Total 8 2a Keeps the leaf afloat/floating/buoyant on the surface of the water 1 R: did not specify location on water 2b Directly under/nearest to the upper epidermis + to absorb/capture as much sunlight as possible for p/s 1 R: did not take reference to upper epidermis 2c In light -dependent stage, chlorophyll absorbs/traps light energy + convert into chemical energy; Light energy is used to split water molecules into oxygen and hydrogen atoms + photolysis of water; In light-independent stage, hydrogen reduce carbon dioxide to glucose / carbon dioxide gains hydrogen to form glucose 1 1 1 Absorbs light Photolysis

+ using the chemical energy from t he light dependent stage; Reduction of CO2 2d 1 1 R: no plateau at the end of graph R: no highest point to indicate optimum temperature; rate must start and end on zero Total 7 3a photosynthesis + leavs contain chlorophyll that traps and converts light energy into chemical energy + provide energy for other organisms in the food web/ does not get energy from other organisms; 1 3b 74 10 2 1 1 1 3c Pyramid of numbers trophic level 4 trophic level 3 trophic level 2 trophic level 1 title with labelled levels; proportionate to the numbers with appropriate scale; consistent width for all levels; 3 R: incorrect and inconsistent scale Total 7 Percentage of carbon dioxide

4a Measure the initial mass of each plant at the start of experiment (M0) + measure the mass of each plant at the end of each day for 10 days (M1, M2, M3, etc.); Calculate the loss of mass each day by finding the difference in mass of each plant and the mass of the plant the previous day (M1-M0, M2-M1, M3-M2, etc.); 1 1 4b Transpiration 1 4c D will lose most mass + D has more leaves than F + more stomata + rate of transpiration is higher in D than F; D will lose most mass + air around D is less humid than air around E which is enclosed in a plastic bag + rate of transpiration is higher in D than E; 1 1 Reason 1 compares with F Reason 2 compares with E 4d To ensure the loss of mass is due to transpiration and not due to evaporation of water from the soil 1 Total 6

5a Asexual reproduction is the process resulting in the production of genetically identical offspring (clones) from one parent; Does not involve the fusion of nuclei of gametes but involves mitosis; 1 1 5b Fertilised egg becomes a zygote + cilia lining the inner surface of the oviduct sweep zygote along oviduct + peristaltic movements in the wall of oviduct also help move the zygote to uterus; zygote divides by mitosis to form embryo + embryo embeds/implants itself in the uterine lining; Amniotic sac encloses the embryo in the amniotic cavity containing amniotic fluid + Support and cushions the foetus before birth/ Shock absorber/ Protects the foetus against physical injury/ Allows foetus a certain degree of movement + promotes muscular development/ Lubricates and reduces friction in the vagina during birth; villi containing blood capillaries of embryo grow from embryo into the uterine wall making up a placenta + separating the fetal and maternal blood systems; placenta allows oxy gen and dissolved food substances eg. glucose, amino acids and mineral salts, to diffuse from the maternal blood system to the fetal blood system/ allows metabolic waste/ excretory products eg. urea, carbon dioxide, to diffuse from fetal blood into the mother’s blood/ allows antibodies to diffuse from mother’s blood to the fetal blood + protecting the foetus against certain diseases/ produces progesterone which maintains the thickness and health of uterine lining during pregnancy; 1 1 1 2 Zygote to uterus Embryo formation & implantation Amniotic sac + 1 function Placenta formation 2 functions of placenta Total 7

6ai 1400 cm3 1 6aii Volume of each breath increases when exercise intensity increases; 1 Relationship 6aiii 1700 × 26 = 44 200 cm3 1 1 6b Aerobic respiration 1 Total 5 7a name Cardiac/heart muscle tissue; function Contracts and relaxes to allow heart to pump the blood in the pulmonary and systemic circulation; 1 1 7bi 5.6 dm3/min 1 7bii 19 – 7 = 12 minutes 1 7biii % increase in heart rate = 168 − 66 66 × 100% =155% 2 1 7biv Heart rate increases rapidly at the start of exercise from 66bpm to 160bpm in the first 2 minutes of exercise; Heart rate increases gradually from 160bpm to 170bpm in the next 2 minutes; Heart rate reaches a plateau at 170 bpm in the last 1 minute of exercise; 1 1 1 R: no quotation of data Total 10

Section B 8a Labelled axes + equal intervals + correct axes; Best fit line; Occupies 2/3 of the grid; All points plotted correctly; 4 8b Lipase digests milk fats into fatty acids; Increasing amounts of fatty acids causes pH to decrease below 8; Phenolphthalein becomes colourless in acidic pH below pH 8; 1 1 1 Enzyme reaction Effect of fatty acids on pH Effect on indicator 8c At 55°C, beyond optimum temperature of 35°C, enzyme/lipase denatures + Lipase cannot bind to milk fats to form enzyme -substrate complex/ active site is altered, no enzyme reaction, no fatty acids formed, pH remains unchanged; 1 8d Optimum temperature from graph 35°C; Temperature at which the time taken for milk to become colourless in the shortest + the rate of enzyme reaction is the highest; 1 1 Quote data Total 10 18 10.5 4 2.5 5.5 12 20.5 0 5 10 15 20 25 20 25 30 35 40 45 50 Time taken to become colourless (minutes) Temperature (degrees Celcius) Graph of time taken to become colourless against temperature

9a 1600 + 700 + 200 – 1500 – 100 – 300 - 200 = 400 cm3 1 9b Water produced by metabolic reactions + catabolic and anabolic reactions; Examples: aerobic respiration + briefly describe; 1 1 9c evaporation of water in sweat will reduce greatly + sweat glands are less active reducing secretion of sweat; water excreted in urine will increase due to increase water potential in blood plasma; evaporation of water from thin layer of moisture in alveoli when breathing out i ncreases due to increase muscular contraction and increase aerobic respiration to release excess