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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, we must consider several factors:
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Proportional Representation: The sizes of the cells in the diagram should be proportional to their sizes in actual blood. Generally, red blood cells are about 6-8 µm in diameter, while white blood cells can be significantly larger, around 12-17 µm. We need to compare these sizes against the sizing in the diagram.
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Cellular Appearance: The diagram should accurately depict the morphology of the cells. For instance, red blood cells are biconcave discs, while white blood cells vary in shape and size (lymphocytes, monocytes, etc.). If the shapes are not represented properly, this affects accuracy.
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Quantity and Diversity of Cells: The representation should include the correct proportion of different blood components (e.g., Platelets, White Blood Cells, etc.) relative to red blood cells. The diagram should show a reasonable number of each type based on their real-life prevalence in the blood.
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Labeling: Properly labeled diagrams should clearly indicate different types of cells, ensuring that they are correctly identified.
In conclusion, assess whether the diagram meets the above criteria and note any discrepancies.
Step 2
Why is it safer to use prepared slides instead of fresh blood?
Answer
Using prepared slides instead of fresh blood is safer for several reasons:
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Infection Control: Prepared slides reduce the risk of transmitting infectious diseases, as they undergo processes that typically involve sterilization and are tested for pathogens.
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Preservation of Specimens: Prepared slides are treated so that the cellular structures remain intact and visible, allowing for better analysis without the complications of altered or degraded fresh blood over time.
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Consistent Quality: Prepared slides provide a uniform standard for observation, ensuring consistent results, unlike fresh blood, which can vary significantly in composition and characteristics depending on the source and handling.
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Ease of Use: Prepared slides are ready for immediate examination, eliminating the need for the preparation process which may introduce contamination or error in sample handling.