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Using a light microscope, a student looked at a prepared slide of human blood, and drew a scaled diagram - HSC - SSCE Biology - Question 18 - 2008 - Paper 1
Question 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 sca... show full transcript
Worked Solution & Example Answer:Using a light microscope, a student looked at a prepared slide of human blood, and drew a scaled diagram - HSC - SSCE Biology - Question 18 - 2008 - Paper 1
Step 1
Assess the accuracy of the diagram.
Answer
To assess the accuracy of the diagram depicting human blood, we can consider several points. Firstly, the proportions of the different types of cells—red blood cells, white blood cells, and platelets—should reflect their actual relative abundance in human blood. Typically, red blood cells are the most numerous, followed by platelets, with white blood cells being the least abundant.
Secondly, the sizes of these cells must be accurate. For instance, a red blood cell usually has a diameter of about 7-8 micrometers, while platelets are much smaller, approximately 2-4 micrometers. If the diagram representation leads to a misleading depiction of sizes, it could affect the viewer’s understanding of the blood's cellular composition.
Lastly, the clarity and detail of the structural features of these cells also play a role in the diagram’s accuracy. Proper labeling of the cells is essential for effective educational reference, ensuring that each cell type’s distinguishing traits are correctly identified.
Step 2
Why is it safer to use prepared slides instead of fresh blood?
Answer
Using prepared slides instead of fresh blood is safer primarily due to the risk of infection and exposure to bloodborne pathogens. Prepared slides are typically treated to eliminate any viable pathogens, making them safe for educational purposes. In contrast, fresh blood can contain bacteria and viruses that pose a health risk to individuals handling the samples. Additionally, prepared slides provide a stable, consistent sample that allows for more controlled observations during microscopy, eliminating variability that may arise from handling fresh samples.