2019 KCSE Marking Scheme

2019 KCSE biology paper 1 marking scheme

1. a)Irritability/sensitivity/Response to a stimulus/stimuli;

b)Reproduction;

2. a) • Shape of the leaf/lamina (broad/narrow);
• (Leaf) margin (smooth/serrated/lobed);
• (Leaf) type (simple/compound);
• (Leaf) sheath/petiole (absence/presence);
• (Leaf) apex (pointed/absent);
• Arrangement/phyllotaxis/phyllotaxy;
• (Leaf) colour/variegation;
(2 x 1) = 2 marks

b) • Has mammary glands;
• Body covered by fur/hair;
• Gives birth/does not lay eggs/is viviparous;
• Has external ears/pinna;
• Has sweat glands;

3. a) Nerve cell/motor neurone;

b)

• Longer axon to deliver/transmit action potential a long way;
• Has (numerous) dendrites for receiving/deliver_ing impulses/transmit impulses;
• Myelin sheath for faster transmission of impulses;
• Schwarm cell for secretion of myelin sheath;
• Nodes of ran vier to enhance speed of transfer of impulses;
• Cell body to control transmission of impulses;
(2 x l)= 2 marks

4 a)Osmosis;

b) Solution E was hypertonic/had more solute molecules compared to solution F/solution F was hypotonic to solution E; by osmosis, water molecules moved through the semi-permeable membrane, G (from solution F to E); hence the decrease in volume of solution F/increased volume of solution E;

c) Semi-permeable membrane/visking tubing/slice of a raw potato/ pawpaw/pig bladder/cellophane paper/dialysis membrane;

b) Atmospheric pressure decreases with the increase in altitude; the imbalance between the ( outer) atmospheric pressure at high altitude and the internal blood pressure (generated by the heart) results in one nose bleeding at higher altitudes/internal blood pressure is higher than the ( outer) atmospheric pressure; OWTTE

3 a) Enables living organisms to avoid dangerous/harmful/harsh climatic/environmental conditions;

OR

– Enables living organisms obtain/access favourable environmental conditions (light, water, oxygen); any one

b (i) Positive phototropism/tip bends towards light; light causes migration of auxins (produced at the tip); to darker side of the shoot, resulting in faster division of cells/elongation on the darker/ opposite side of the shoot, hence bending towards light;

(ii) Both seedlings remain upright; seedling II does not have the
tip while in III the tip has been covered by an opaque material preventing light from causing unequal distribution of auxins; OWTTE

(iii) Fitting an agar block treated with auxins at the decapitated end of seedling 11; removing the opaque material covering the tip of seedling Ill/replacing the opaque cap with a transparent one;

2019 KCSE biology paper 3 marking scheme

1 a) i- Specimen F has thorns/spikes that prick herbivores/mammals;

– Photograph E, the plant normally produces a (white) unpleasant/poisonous/harmful fluid/liquid/substance;
– Photograph H, the plant has thorny leaves/produces an unpleasant/poisonous fluid; Has thick cuticle to reduce transpiration
(3 marks)

ii- Specimen F: Habitat- terrestrial habitat (with average/moderate rainfall/water); leaves fold to conserve water ( during drought); ( 2 marks) Photograph E: Arid/semi-arid/desert habitat; thick/fleshy stem that stores water/fluid; leaves reduced in size/number/size; (2mks)

– Photograph H: Arid/semi-arid/desert habitat; plant leaves fleshy storing water; thick/has muscillage. (2mks)