Download MARKING SCHEME BIOLOGY P1 231/1 1. a)Cohesion Water

MARKING SCHEME
BIOLOGY P1
231/1
1. a)Cohesion
Water molecules cling to each other maintaining a continuous column of
water/preventing the break of water column;
b)Adhesion
Water molecules cling to the sides of the xylem vessel walls;
2. Independent assortment
Crossing over
3. (i) Concentrate light on the object on the stage;
(ii) Supports the eye piece and the revolving nose piece;
4.a)Epicotyl;
(1mark)
(b) It enables the seedling to be firmly anchored in the ground;(2marks)
- It enables the seedling to obtain water and mineral salts;
5. (a) anaerobic respiration.
(b) Glucose
Ethanol + Carbon (IV) oxide + Energy
(c) To remove oxygen; cooling provide suitable temperature for enzymatic reaction /avoid
destroying/killing yeast
6.a- Catalase;
b-Liver;
C-Breakdown of toxic hydrogen peroxide into harmless products/water and Oxygen
7.a) Photolyis to provide hydrogen atoms required in the dark stage of photosynthesis;
Synthesis of more/additional ATP required in the dark stage of photosynthesis;
b) Starch is insoluble /osmotically inactive (hence does not affect the osmotic pressure of plant
cells)
8.a) (i) 20 chromosomes;
(ii) 40 chromosomes;
9.(i) Identical twins arise when a male gamete fertilizes one ovum that divides into two; and
develop into separate embryos;
(ii)Fraternal twins arise when male gametes fertilizers two ova from different ovaries at ago.
10.a) To breakdown non-reducing sugars into reducing sugars
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b) To neutralize hydrochloric acid
c) Condensation
11.a) For respiration to produce energy;
(b) Store food; protect the shoot;
12.a) More urine will be produced / dieresis;
b)Lack of Anti - diuretic hormone / vasopressin therefore less water is reabsorbed;
13. Results in adaptations that enable organisms to exploit different ecological niches;
Leads to the formation of new species;
14.(a) Aquatic ecosystem;
(b) The shorter the food chain, the more energy can be derived from it, hence the larger the
population it can support;
15. ProphaseI ;( Reject wrong spelling/prophase 1/i)
b) Recombination of genes; leading to variation;
16. Haemolysis is the process by which red blood cells take in water till they burst; while
plasmolysis is the loss of water from plant cell until membrane is detached from cell wall/flaccid.
17. Observation of the mode of feeding; Examining the droppings; Dissecting of the gut;
Analyze the gut contents; Studying their dentition/beaks/claws/mouth parts;
18.a)Luteinizing hormone, RJ LH
b) Causes ovulation; Induces Grafian follicle to become corpus luteum; Stimulates corpus
luteum to release progesterone;
19.a) Animal B: ammonia;
Animal C: Uric acid;
(b) Posses larger glomeruli to increase ultra-filtration;
Possesses a shorter loop of Henle to minimize reabsorption of water;
20(a) Moist to dissolve the diffusing gases across the respiratory surface
(b) Thin to reduce distance covered by diffusing gases i.e. for the gases to diffuse through short
distance.
(c) Many palisade cells in a small area to enable them receive maximum sunlight.
21.a) tannin – manufacture of ink; dyeing/printing of fabric/ softening of leather/treatment of
Leather/ conversion of hides / skin/tanning of leather;
b) Quinine – treatment of malaria.
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c) Caffeine – stimulant used in beverages; acc increased mental activities/reduce fatigue
22. Thin walled for easy diffusion of gases
Large air spaces/store a lot of air which makes the plant buoyant/gaseous exchange
23. Arteries have thick muscular walls; veins have thin less muscular walls;
Arteries have narrow lumen, veins have wider lumen;
Arteries have no valves except at junction with heart; veins have valves at regular intervals;
24.Reduces competition between two different stages;
Pupa can survive adverse conditions/pupa is a non-feeding stage;
Dispersal prevents overcrowding;
25.a) Pitfall trap;
b) For catching crawling animals;
26.(a) C – G – G – C – T – A – A – A – T – G – C – C
(b) C – G – G – C – U – A – A – A – U – G – C – C
27.(a) Phylum Chordata;rj Chordate/Chordates
b) Class Mammalia; rj mammals
28. Form vesicles that transport materials to other parts of the cell e.g. proteins;
Transport secretions to the cell/ surface for secretione.g. enzymes and mucus;
They form Lysosomes;
29. Competition; Predation; Parasitism; Symbiosis; Saprophytism ;( Any correct three)
30. Replace the new born baby’s blood with that of the mother’s rhesus
Treat the mother with ant-rhesus globulin that prevents antigen-antibody reaction;
31. Vitamins; Mineralsalts ;( Rj Minerals alone,) Water; Acc Roughages;
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