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MUTOMO / IKUTHA DISTRICTS KCSE PACESETTER - 2011 BIOLOGY – PAPER 1 MARKING SCHEME 1. Contain lytic enzymes√, that breakdown foreign material, which can be ingested instead of food.√ (2 mks) 2. Water vapour accumulates in the depression of stomata lowering the water vapour concentration gradient hence reducing the rate of transpiration;√ - Water vapor accumulates in the depression where it cannot be blown away by wind, this increases the saturation reducing the rate of transpiration.√ (2 mks) 3. Lactic acid√; Energy√ (2 mks) 4. a) X – White blood cell/ Leucocyte√ Y – Red blood cell/ Erythrocyte√ rej white cell acc + neutrophil Rej red cell rej (germs) b) Large lobbed nucleus√ 5. a) allow transmission of nerve impulse in one direction√ Or control memory/ learning (any) b) Post-synaptic membrane √ rej pre-synaptic membrane rej membrane alone c) - Presence of numerous mitochondria for energy production√(mark first correct answer) - Presence of vesicle which contain a transmitter substance 6. a) T-A-A-G-C-T√ b) U-A-A-G-C-A√ c) DNA Double stranded√ RNA Single stranded Has base Thymine in addition to Adenine, Has base Uracil in addition to Adenine, Cytosine and Guanine Cytosine, Guamine√ Has deoxyribose sugar Has ribose sugar Mark any correct two 7. Sunken stomata√ Reduced leaf size√ Succulent leaf and stem√ 8. a) Meiosis is a type of cell division where a single parent cell divides to form four haploid daughter cells while mitosis a single cell divides to form two haploid daughter cells.√OWTTE b) Lead to formation of haploid gamete cells that through fusion maintains the diploid state of the species√ 9. a) Gill√ b) Creates a large surface area for maximum gaseous exchange√ c) Large and curved to provide large surface for attachment of numerous gill filaments bony, rigid – to offer support 10. - Grass increases√ - Blackbirds decreases√ 11. - Peristalsis√ -Churning of food√ 12. a) Area = x 2000 x 2000 = 125714.29 Nm2 b) 1 = 25142.858 m 13. - Multiplies faster/ rapidly in red blood cells - Cannot be digested by enzymes in the vector - It mutates or develops resistance to drugs 14. a) - high chance of survival since zygote is highly protected in the body - High chances of fertilization b) Most of the excess amino acids are used in the development and growth of the foetus thus less amino acid are deaminated 15. After first transfusion nothing happens but the patient produces antibodies After second transfusion, there will be antigen-antibody reaction within the body of the patient This causes agglutination i.e. clumping together of red blood cells There is thus the problem in oxygen transportation leading to death of the patient 16. Absorbs latent heat of vapourization leading to cooling 17. Active transport Cytoplasmic streaming 18. a) Catalyses the breakdown of toxic Hydrogen peroxide to harmless products i.e. water and oxygen in active tissues b) Very high temperatures above optimum ExtremePh 19. Gametophyte is the dominant Presence of rhizoids Lack of vascular tissue 20. a) M – Triceps N – Biceps b) M – contracts N – Relaxes 21. a) A – white matter D – Grey matter b) Cerebrospinal fluid c) Shock absorber Provide nutrients 22. a) structures which have become reduced and are functionless b) Appendix Coccyx (vestigial tail) 23. To allow light to fall through the specimen for visibility To avoid damaging of cells and tissues 24. Nitrogen Magnesium 25. Diabetes mellitus – disease caused by failure or less production of insulin hormone hence sugar/glucose being present in urine Diabetes inspidus – disease caused by the failure or no production of ADH hormone hence passing large amount of dilute urine. 26. a) Autotrophs are organisms that utilize simple substance to manufacture complex synthesized organic substances. Heterotrophs depend on complex synthesised organic substances b) Test cross – cross between an individual of unknown genotype with a double recessive genotype Back cross – cross between an offspring with one of the parents 27. a) Ability of the eye to bring into sharp focus distant and near object b) Radial muscle relax, circular muscles contract to reduce the size of the pupil 28. Production of low urine volume Production of concentrated/ hypotonic urine 29. a) Juvenile hormone – controls metamorphosis in young insects b) Abscisic acid – formation of abscission layer in leaves and fruits 2