Biology 3 Nov/Dec 2011 - Candidates Weakness

Biology Paper 3,Nov/Dec 2011

Questions:		1	2	4		Main

General Comments
Weakness/Remedies
Strength

Question 2
( (a) (i) Identify the structure in the diagram ------------------------------------------------------------------------------------------------------------------ [ 1 mark ] (ii) Name the parts labeled I to X I. ………………………………………………………… VI. …………………………………………………………….. II. …………………………………………………………. VII. ……………………………………………………………. III. ………………………………………………………… VIII. …………………………………………………………… IV. ……………………………………………………….. IX. …………………………………………………………… V. ………………………………………………………. X. ……………………………………………………………. [ 5 marks ] (iii) State the function of the parts labeled II, III, V, VII and IX II. …………………………………………………….. VII. ………………………………………………………….. III. ……………………………………………………. IX. …………………………………………………………… V. ……………………………………………………. [ 5 marks ] (b) What happens to the part labeled VIII in: (i) Bright light:…………………………………………………………………………………………………………….. ……………………………………………………………………………………………………………………………… (ii) Dim light:………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………………………… (c) (i) List four defects associated with the structure in the diagram. ……………………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………………………….. ……………………………………………………………………………………………………………………………….. [ 4 marks ] (ii) State ways in which each of the defects in 2(c)(i) above can be corrected ……………………………………………………………………………………………………………………………... …………………………………………………………………………………………………………………………….. ……………………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………………… [ 4 marks] (d) Outline four ways by which the structure in the diagram can be taken care of. …………………………………………………………………………………………………………………………….. ……………………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………………………. [ 4 marks ]
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COMMENT
This was the most popular question in this paper and the performance of the candidates was good. Most candidates could correctly identify the structure as the eye and correctly name the labeled parts. A few candidates however lost marks due to spelling errors. Most candidates could not correctly spell “conjunctiva “ right. Again most candidates could correctly state the functions of the labeled parts however in stating the functions of the optic nerve some candidates stated that it carried images rather than impulses to the brain and so lost the score. Most candidates were stating the reaction of the pupil rather than the iris to light changes and many candidates made mistakes in outlining correction of eye defects. Effect of light changes on the iris . Dilates/elongates in bright light Contracts/shortens in dim light. Defect (ii) Correction Short sightedness/Myopia Concave/diverging lens Long sightedness/Hypermetropia Convex/converging lens Astigmatism Cylindrical lens Presbyobia Bifocal lenses Cataract Surgery Pterigium Medical Most candidates could however state how the eyes should be cared for and scored high marks.