waecE-LEARNING
Biology Paper 3,Nov/Dec 2012  
Questions:   1 2 4   Main
General Comments
Weakness/Remedies
Strength

















































Question 2


Two identical leafy shoots E and F from a shrub, were each connected to a potometer.  One was placed under normal laboratory conditions and the other under a fan in the laboratory.  The distance moved by each bubble in each potometer was recorded at regular  time intervals.

The results obtained are shown in the table below.

Study the information in the table carefully and use them to answer question 2(a) to 2(f).

Time after start of experiment
(mins)

Distance moved by each bubble (mm)

Shoot E (normal) laboratory condition)

Shoot F (in the laboratory under the fan)

0

0

0

5

3

5

10

5

10

15

8

18

20

11

28

25

13

33

 

 

 

 

 

 

  1.   Plot two graphs, one for each shoot on the graph sheet provided, with the distance

   moved by the bubble on the vertical axis (y) and the time on the horizontal axis (x).

 

 

 

 

 

 

 

 

 

 

 

 

 

 


  1.   (i)   Under which condition did the bubble move faster?

        
        ………………………………………………………………………………………
                                                                                                     [ 1 mark ]

(ii)    Explain the effect of the fan on the shoot.
         
        ………………………………………………………………………………………

        ………………………………………………………………………………………
                                                                                                   [ 3 marks ]

  1.  What is the aim of the experiment?

Aim of experiment:
……………………………………………………………………………………
……………………………………………………………………………………
                                                                                       [2 marks ]

  1.  (i)  Name the physiological process experienced by the leafy shoots

                  ……………………………………………………………………………………..
                                                                                                             [ 1 mark ]

  1. Name one structure of the leaf  associated with the process named in 2(c)(i) above.

…………………………………………………………………………………
                                                                                        [1 mark ]

_____________________________________________________________________________________________________
COMMENT

             Most candidates performed below average in this question because most of them could not give the correct  title to the graph; identify the vertical axis (y), and horizontal axis (x); give the correct scale used; plot correct points and rule the lines of the graph.  Some candidates also plotted two graphs separately instead of being on the same section of the graph sheet.
          Many candidates could give the condition under which the bubble moved faster.
          but were not able to explain the effect of the fan on the shoot and
          the aim of the experiment.  Many candidates wrote ‘osmosis,’; photosynthesis’ as
          the physiological process; and some also wrote ‘lenticel’ instead of ‘stomata’as the
          part of the plant associated with the process.

              Expected answers include
           2  (a)       Graph
                       
Title (TL) of the Graph – Effect of wind/fan on water loss/transpiration from plant shoots/Effect of fan on the movement of air bubble in a potometer                                                                                                                                          
Labelling of axis (LA)                                                                     

Scale for X and Y (SC)                         
Labelling of graphs (LG)                      

Correct points plotted (CP)                                     

               Ruled lines (RL) to pass through the points      
                 Note: The scales must correspond to the graphs.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

         

 

 

    (b)(ii) Effect of fan/breeze/wind on shoot

  • Wind/breeze generated by the fan removes water vapour, above the stomata;
  • Creating a greater moisture gradient/transpiration pull;
  • In the external environment/atmosphere of the shoot;
  • Making water vapour move faster out of the leaf;
  • Causing more water to be absorbed by the shoot/root of shoot.

                                                                       
 (ii)    Aim of experiment
 
  To study the effect of environmental conditions/wind/breeze; on the rate of
   transpiration/water loss by shoots.
                                                                               
          (c) (i)  Physiological process

                   Transpiration                                                       

  • Part of leaf

 

  •   Stomata/stoma
  •   Guard cell(s)                                             

 

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