igcse model questions vol1 2020 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 2020 biology (Practical) questions designed to simulate the real exam environment.

Practice these randomly selected questions to test your readiness.

Question 1 View Details
A sample of cheek epithelial cells is prepared on a slide using a drop of methylene blue stain. The slide is examined under a light microscope equipped with an ocular micrometer calibrated at 0.01 mm per division.
Question Parts
(a)
Describe the procedure for preparing the slide and observing the cells under the microscope.
(b)
Using the ocular micrometer, the following five cell diameters (in divisions) are recorded from five different fields: 23, 27, 25, 24, 26. Calculate the average cell diameter in micrometres (µm). Show your working.
(c)
Assuming the cells are approximately spherical, calculate the average cell volume in cubic micrometres (µm³). Use V = \(\frac{4}{3}\pi r^{3}\) and take \(\pi = 3.14\). State any assumptions and comment on one possible source of error in the volume determination.
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 investigates mitosis in the root tip of an onion (Allium cepa). The root tip is harvested, fixed in 1 % acetic acid, stained with Feulgen stain, and a squash preparation is made for observation under a light microscope.
Question Parts
(a)
Outline the steps required to obtain a suitable squash preparation for observing mitosis in the onion root tip.
(b)
In the prepared slide the student examines 10 randomly selected fields and records the number of cells observed and the number of cells in mitosis as follows: Field 1: 120 cells, 6 mitotic Field 2: 115 cells, 5 mitotic Field 3: 130 cells, 7 mitotic Field 4: 118 cells, 4 mitotic Field 5: 122 cells, 6 mitotic Field 6: 119 cells, 5 mitotic Field 7: 124 cells, 6 mitotic Field 8: 117 cells, 5 mitotic Field 9: 121 cells, 7 mitotic Field 10: 123 cells, 6 mitotic Calculate the mitotic index (percentage of cells in mitosis) for the whole slide. Show all calculations.
(c)
Explain what a high mitotic index indicates about the growth activity of the root tip and suggest one factor that could artificially increase the observed mitotic index.
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 student prepares a simple diet plan for a 12‑year‑old pupil. The daily menu consists of the following foods: - 150 g of boiled rice (carbohydrate 28 g per 100 g, protein 2.5 g per 100 g, fat 0.3 g per 100 g) - 100 g of grilled chicken breast (protein 31 g per 100 g, fat 3.6 g per 100 g, carbohydrate 0 g) - 80 g of mixed vegetables (carbohydrate 7 g per 100 g, protein 2 g per 100 g, fat 0.2 g per 100 g) - 250 ml of whole milk (carbohydrate 5 g per 100 ml, protein 3.3 g per 100 ml, fat 3.5 g per 100 ml) The Atwater factors are: carbohydrate 4 kcal g⁻¹, protein 4 kcal g⁻¹, fat 9 kcal g⁻¹. The recommended daily intake for a 12‑year‑old is 2000 kcal, with at least 50 g protein, 260 g carbohydrate and 70 g fat. Answer the following:
Question Parts
(a)
Calculate the total energy (kcal) supplied by the diet.
(b)
Calculate the percentage contribution of each macronutrient to the total energy.
(c)
State whether the diet meets the recommended intake for energy, protein, carbohydrate and fat. Provide a brief justification for each nutrient.
(d)
Suggest one specific change to the diet that would improve its overall nutritional balance and explain why it would be effective.
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
A group of students investigates the effect of temperature on the rate of aerobic respiration in baker's yeast. In each trial 5 g of dry yeast is mixed with 50 ml of 5 % (w/v) glucose solution in a sealed 250 ml conical flask fitted with a delivery tube leading to an inverted graduated cylinder (capacity 100 ml) filled with water. The volume of CO₂ collected in the graduated cylinder is recorded for 10 minutes at three different water‑bath temperatures. Data obtained: | Temperature (°C) | Volume of CO₂ collected (ml) | |------------------|------------------------------| | 25 | 12.5 | | 35 | 22.8 | | 45 | 38.1 | Answer the following:
Question Parts
(a)
Calculate the rate of CO₂ production (ml min⁻¹) at each temperature.
(b)
Determine the percentage increase in the rate of respiration when the temperature is raised from 25 °C to 35 °C, and from 35 °C to 45 °C.
(c)
Identify one probable source of systematic error in this experiment and suggest a method to minimise it.
(d)
Explain, using enzyme theory, why the rate of respiration increases with temperature up to a point and why it would eventually decline if the temperature were raised further.
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