igcse model questions vol1 2018 biology | Practical

Prepare for your exams with igcse model questions vol1 questions? Reviewing past/model questions is one of the most effective ways to guarantee a high score. This practice hub features authentic 2018 biology (Practical) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1 View Details
A student is investigating the size of plant cells using a compound microscope. The student prepares a slide of a thin transverse section of an onion epidermis and uses an ocular micrometer that has been calibrated with a stage micrometer. The calibration shows that 1 division on the ocular micrometer corresponds to 0.005 mm at the total magnification used (400×).
Question Parts
(a)
The student measures the length of three typical cells and records 28, 30 and 32 ocular divisions respectively. Calculate the average actual length of a cell in micrometres (µm).
(b)
The width of the same cells is measured as 12, 13 and 11 ocular divisions respectively. Calculate the average actual width of a cell in micrometres (µm).
(c)
Assuming the cell is a rectangular prism whose depth is equal to its width, estimate the cell’s volume and surface area. Show the formulas you use and give the final answers in µm³ and µm² respectively.
(d)
Explain how the surface‑area‑to‑volume ratio you have calculated influences the rate at which nutrients can diffuse into the cell.
Detailed Essay Solution & Marking Scheme Available

Get the step-by-step mathematical proofs, key points required by examiners, and a comprehensive breakdown from our AI Tutor.

Reveal Answer
Question 2 View Details
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.
Detailed Essay Solution & Marking Scheme Available

Get the step-by-step mathematical proofs, key points required by examiners, and a comprehensive breakdown from our AI Tutor.

Reveal Answer
Question 3 View Details
A group of students investigated the effect of different carbohydrate solutions on the heart rate of the freshwater crustacean Daphnia magna. Five Daphnia were placed in each of three separate beakers containing: (i) distilled water (control), (ii) 5% glucose solution, and (iii) 5% sucrose solution. After a 5‑minute acclimatization period, the number of heartbeats in 60 seconds was recorded for each Daphnia. The data obtained are shown in the table below. | Solution | Daphnia 1 | Daphnia 2 | Daphnia 3 | Daphnia 4 | Daphnia 5 | |----------|-----------|-----------|-----------|-----------|-----------| | Distilled water | 120 | 115 | 118 | 122 | 119 | | 5% Glucose | 130 | 135 | 132 | 128 | 134 | | 5% Sucrose | 125 | 127 | 124 | 126 | 128 | Using this data, answer the following questions.
Question Parts
(a)
Calculate the mean heart rate (beats per minute) for Daphnia in each solution.
(b)
Which solution produced the highest mean heart rate? State the value.
(c)
Suggest one possible source of error that could affect the reliability of the results.
(d)
Propose one improvement to the experimental procedure that would reduce the error you mentioned in part (c).
Detailed Essay Solution & Marking Scheme Available

Get the step-by-step mathematical proofs, key points required by examiners, and a comprehensive breakdown from our AI Tutor.

Reveal Answer
Question 4 View Details
Students measured the rate of respiration of germinating broad‑bean (Vicia faba) seeds using the soda‑lime method. Three sets of five seeds each were placed in sealed chambers kept at different temperatures: 25 °C, 35 °C and 45 °C. The volume of carbon dioxide absorbed by the soda‑lime (in millilitres) over a 5‑minute period was recorded for each trial. The results are shown below. | Temperature (°C) | Trial 1 | Trial 2 | Trial 3 | Trial 4 | Trial 5 | |------------------|---------|---------|---------|---------|---------| | 25 | 12 | 13 | 11 | 14 | 12 | | 35 | 20 | 22 | 19 | 21 | 20 | | 45 | 25 | 27 | 26 | 28 | 27 | Using the data, answer the following questions.
Question Parts
(a)
For each temperature, calculate the average rate of respiration in millilitres of CO₂ per minute.
(b)
Calculate the percentage increase in the respiration rate when the temperature is raised from 25 °C to 35 °C, and from 35 °C to 45 °C.
(c)
Explain why the rate of respiration increases with temperature, referring to the role of enzymes.
(d)
Identify two possible sources of error that could affect the measured respiration rates.
(e)
Suggest one improvement to the experimental set‑up that would reduce the error(s) you mentioned in part (d).
Detailed Essay Solution & Marking Scheme Available

Get the step-by-step mathematical proofs, key points required by examiners, and a comprehensive breakdown from our AI Tutor.

Reveal Answer

Master the Exam!

You've seen a preview, but there are thousands more questions plus AI tutor to break down complex solutions.

Unlock Full Access Available for Android & Windows
Help others prepare! Share this practice hub:
Chat with Support