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BIOLOGY, M1 2008 HSC 18

Using a light microscope, a student looked at a prepared slide of human blood, and drew a scaled diagram.

The diagram shown is a representation of the student's scaled diagram.
 

  1. Assess the accuracy of the diagram.  (3 marks)

  2. Why is it safer to use prepared slides instead of fresh blood?  (1 mark)

Show Answers Only

a.    The diagram has the following inaccuracies:

→ The scale is wrong as red and white blood cells are much smaller. A more accurate scale would use micrometres as apposed to millimetres.

→ Relative size of red and white blood cells is wrong, as WBC’s are on average 1.5 – 2 times bigger than RBC’s.
 

b.   A slide with fresh blood could contain pathogenic bacteria, leading to disease.

Show Worked Solution

a.    The diagram has the following inaccuracies:

→ The scale is wrong as red and white blood cells are much smaller. A more accurate scale would use micrometres as apposed to millimetres.

→ Relative size of red and white blood cells is wrong, as WBC’s are on average 1.5 – 2 times bigger than RBC’s.
 

b.   A slide with fresh blood could contain pathogenic bacteria, leading to disease.