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EKSIKA -2016 BIOLOGY PAPER 2 (THEORY) 231/2 MARKING SCHEME Rej Capital letters Rej commars Check correct ordericpmm Lined dividing upper and lower jaw Must be clearly shown 1.a) (i) 2 C 1 2 1 pm 2 2 m; (ii) Upper jaw 8 Lower jaw 8 total 16×2 =32 3 3 b) Salivary smylase/ptyalin; c) X Y Canines; Molar; Pointed for tearing flesh rej chisel shaped Have cusps and ridges/wide surface for crushing/chewing (food); ref strong d)Periodontis/periodontal disease/ginginitis/pyorrhoes Acc. Periodontal - Dental carries; Hormone 8 Source 2.a) Glucagon; Pancreas; Pituitary gland; Function Stimulate absorption and re absorption of salts Na+ into blood Stimulate reabsorption of water back into bloodstream; b) All Glucose is reabsorbed back into bloodstream along kidney nephorome under influence of insulin hormone; c) to reduce the surface area for transpiration; to conserve water in the plant; to eliminate accumulated wastes on leaves (8mks) 3. a(i) M-Glycolysis; N- krebs cycle/tric acid cycle/ incarboxylic 8acid cycle; ii) pyruric acid; b)M- cytoplasm; N- Mitochondria / matrix of mitochondria; c) RQ = CO2 Produced =56;=0.7; O2Consumed =80 d) Ethanol/ethylacohol; 8mks 4. a) X- blood platelets/thrombocytes; Y- white blood cells/lencocytes; b) X-involved in blood clotting; Y- Protection against pathogens/disease causing organisms; A.C. correct examples rej germs c) Biconcave shaped to increase surface area for diffusion of oxygen/gases; Numerous for efficient transportation of gases; d) magnification = actual length = image length = 40mm; magnification 50000 (1mm=1000micrometers) 40 ×1000 image length = actual length um = 8um 8 5000 5. A) a- corolla/petal; D- Ovule; mark on diagram. reject sees b) B Stigma) C Anther Insect pollicated Small/ sticky stigma Rej shor Short/small anthers (which are firmly attached to filatement Wind pollinated Long/feathery stigma; Long/large anthers (which are loosely attached to filatement ; c) Integument develops into seed coat/testa Zygote embryo Triploid nucleus endosperm Ovary wall pericarp Ovary fruit Ovules seeds Corolla/petals/style/sepals/spemens/filament/dry only fall off/withers (MARK 1ST 2) d) Division ; spermatophyte; class : Dicotyledonae; 8 SECTION B 6.a) 11 Hours; and 31 Hours; Acc. 30hours b) (i) A and B The number of bacteraial dividing are few; Bacteria are adjusting to hew environment; Hence low increase in population (ii) B and C More cells ae fivding; due suitable environment/adjusted to new environment/fanurable conditions; few dying; therefore high increase in population; (iii) C and D No population change; number produced is equal to number dying; (acc- number for pop and many for more) c) accumulation of toxic wastes; that kills bacterial; depletion of nutrients; leading to death; overcrowding ; leading to competition for space/food; mark 4 award death of bacteria once d) (i) The population will remain the same; (ii) Temperature not conducive for division; rej(ii) if (i) is wrong e) For food to be sufficient/adequate; for social amenities/Education/clensing/ employment to be adequate; for health services to be adequate; land space is not increasing/ to avoid overexploitation of land; reduced crime rate; acc. Prostitution as crime rej. Reduced immorality any first 3 7. (a) Searching for food/water/ shelter; Migration away from unfavourable places/natural disasters/catastrophies, fire, floods; Escape from predators/enemies; Dispersion/colonization of new areas; 4mks b) – the vertebral column consists of a series of vertebra held together loosely so that it is flexible; myotomes/muscles; associated with vertebral column produces movement; the sideways and backwards thrust of the tail and body against water; results in resistance of the water pushing the fish sideways and forward in a direction opposed to thrust; head not flexible; so as to maintain the forward thrust body streamlined; to reduce resistance (so swim smoothly); presence of fins; help in propulsion/balance; paired fins (pectoral and pelvic); for controlling pitch and string dams movement; unpaired fins (divsal, ventral, anal); for preventing yawing and rolling presence of swim bladder; make fish buoyant scale overlap forward the back; provide smooth surface/reduce water resistance; 16mks 8. Gaseous exchange in terrestrial plants Gaseous exchange takes place in spongy mesophyll; During the day air diffuses into large air spaces of spongy mesophyll; through stomata; The carbon(iv) oxide in the air diffuses into photosynthetic cells; in solution form;. During photosynthesis carbon (iv) oxide is used; while oxygen is produced; some of the oxygen is used in respiration; while the rest/some of the oxygen diffuses out of the leaf; through stomata. During night, air diffuses into air spaces of spongy mesophyll; the air dissolves into film of moisture; The oxygen in the air diffuses into cells; and is used in respiration; during which carbon (iv) oxide is produced; the carbon (iv)oxide diffuses out of the leaf; through stomata due to concentration/diffusion gradient; At night carbon(iv)oxide accumulates in the leaf since photosynthesis does not take place; Some gaseous exchange also takes place through cuticles ; gaseous exchange occurs through epidermis of young leaves and stems; Epidermis of the root carries net gaseous exchange with air int the soil some plants have breathing roots through which gaseous exchange occurs; ACC.pheumatophurnves Gaseous exchange occurs through lenticles (found in older stems); The cork cells at a lenticels are intensely produced; Gaseous exchange takes place between cork and atmosphere within the loosely packed cell; 25mks