Alternative Practical grade 11
Answer all questions.
(i) Draw a large diagram to show the layers present in the leaf section in Fig 1
Do not draw any cells
(ii) Measure the thickness of the leaf along the line AB on Fig 1
Calculate the actual thickness of the leaf using your measurement and the formula, include the
units.
Magnification = Length of line AB on Fig 1
Actual thickness of leaf
(iii) Label the layer on your drawing with the letter X to show where this type of tissue is
found.
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(b) scientist carried out an investigation into the effect of light on the growth of
leaves.
Plants of the same species (A) were grown in three different light intensities. the
plants were grown in the same soil and kept in glasshouses with automatic watering.
A sample of 100 leaves was selected at random and collected from plants in
each of the three different light intensities. A total of 300 leaves were collected.
The scientist studied the variation in the size and structure of the leaves in each
sample.
(i) Suggest why the scientist used large sample of
leaves.________________________________________________________________
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(ii) Suggest why the leaves in each light intensity were selected at
random._______________________________________________________________
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(iii) A grid, divided into millimetre squares, was used to measure the surface
area of the leaves.
Outline how the grid could have been used?
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(iv) State the variable that was changed (independent variable) in this
investigation.
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(c) The scientists collected data from one other plant species (B)
Table 1 shows the results.
(i) Calculate the percentage difference in the average leaf area for species A from a
light intensity of 50 arbitrary units to 10 arbitrary units.
Show your working and give your answers as percentage to the nearest whole
number.
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(ii) Plot a bar chart on the grid to show the average leaf area for species A and B at
each light intensity.
(iii) Describe the trends shown in your graph for species A and specie B .
(iv) The scientist wants to determine more precisely the light intensity that results in the
largest leaf area for species B.
Suggest how the method used in the investigation could be modified to achieve
this?
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