Igcse Model Questions Vol1 2018 Biology Question 2

Practice practical question 2 from the 2018 Igcse Model Questions Vol1 Biology examination. This question covers Cell Division, Mitosis, Microscopy, Experimental Design .

Igcse Model Questions Vol1 2018 Biology Practical
Topics: Cell Division Mitosis Microscopy Experimental Design
Question 2 IGCSE_MODEL_QUESTIONS_VOL1 • 2018 • BIOLOGY • practical

A student prepares a slide of an onion root tip that has been stained with aceto‑orcein to observe mitosis. Using a microscope set at a total magnification of 1000×, the student examines five fields of view, each containing 50 cells. The numbers of cells observed in the different phases of mitosis in each field are recorded as follows: Field 1: 8 prophase, 5 metaphase, 2 anaphase, 1 telophase. Field 2: 7 prophase, 6 metaphase, 3 anaphase, 2 telophase. Field 3: 9 prophase, 4 metaphase, 1 anaphase, 1 telophase. Field 4: 6 prophase, 5 metaphase, 2 anaphase, 2 telophase. Field 5: 8 prophase, 5 metaphase, 2 anaphase, 1 telophase.

Question Parts

( a )
Calculate the total number of cells examined and the total number of cells observed in each mitotic phase (prophase, metaphase, anaphase, telophase) across all five fields.
( b )
Determine the mitotic index (MI) for the root‑tip cells, using the formula MI = (Number of cells in mitosis / Total number of cells) × 100. Include all four phases as mitotic cells.
( c )
The proportion of cells in metaphase appears higher than expected. Suggest two possible reasons for this observation that relate to the experimental procedure.
( d )
Design a brief experiment to compare the mitotic index of onion root‑tip cells grown under normal conditions with those exposed to a growth‑inhibiting chemical. State the control, the variable, the method of data collection, and how the results would be analysed.

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About This Question

This is Igcse Model Questions Vol1 2018 Biology Question 2. It is one of the practical questions from the 2018 Igcse Model Questions Vol1 Biology examination.

The question covers Cell Division, Mitosis, Microscopy, Experimental Design .

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