Health Science Paper 1, May/June 2007

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Questions:	1	2	3	4	5	6	7	8	Main

General Comments
Strength
Weakness/Remedies

Question 4

The experimental set up in the diagrams below illustrates the mechanism, of breathing in humans.

Use it to answer 4(a) and 4(b).

Air out

_____________________________________________________________________________________________________

OBSERVATION

(a) . Name the structures in mammals that are equivalent in function to the parts labelled:
                 (1)        glass tube;
                 (11)      bell jar;
                 (iii)       balloons;
                 (iv)       X;
                 (v)        Rubber sheet.                                                                       [5marks]

      (b)       Name the processes illustrated in the diagrams A and B                  [2 marks]
       (c)      . State the function of the rubber sheet in the set up.                        [2 marks] .
      (d)       State one precaution to be taken. in setting up the experiment illustrated.
[1 mark]
This question was based on an experimental set up to illustrate the mechanism of breathing in humans. Many candidates totally avoided this question, and the few who attempted it performed poorly.

255 Most of the candidates who attempted the question were able to name the equivalent parts of the set up in mammals and scored 'well in that sub-number, however they could not identify the processes in diagrams A and B as inspiration and expiration. Instead of stating the function of the rubber sheet/diaphragm in the mechanism of breathing, they were stating anatomical functions e.g. separating the chest abdominal cavities. Most candidates who attempted the question could not state the precaution to be taken in carrying out the illustrate experiments expected answers include:
The rubber sheet causes decrease or increase in air pressure in the set-up; causing air to flow in or out.
Precaution
Keep the set up air tight: