Total marks: 100 · Duration: 105 minutes · Tier: Higher
Instructions to candidates
- Use black ink or ball-point pen.
- Answer all questions.
- In calculations, show all your working and give the unit of your answer.
- You may use a calculator.
- For multiple-choice parts, choose one answer, A, B, C or D.
- Where a question describes apparatus, a graph or a diagram in words, you may find it helpful to sketch it.
Information
- The total mark for this paper is 100.
- The marks for each question are shown in brackets.
- In questions marked with an asterisk (*), marks will be awarded for your ability to structure your answer logically, showing how the points that you make are related or follow on from each other where appropriate.
- This paper covers Edexcel GCSE (9–1) Biology Paper 2 content: topic 1 (key concepts in biology) and topics 6 to 9: plant structures and their functions; animal coordination, control and homeostasis; exchange and transport in animals; and ecosystems and material cycles.
Paper
Question 1 — Photosynthesis (10 marks)
In a core practical, a student investigates the effect of light intensity on the rate of photosynthesis. She places a piece of pondweed in a test tube of sodium hydrogencarbonate solution and counts the bubbles of gas given off in one minute with a lamp at different distances.
| Distance from lamp (cm) | 10 | 20 | 30 | 40 |
|---|---|---|---|---|
| Bubbles per minute | 64 | 18 | 8 | 4 |
(a) Write the word equation for photosynthesis. [2 marks]
(b) Explain why the student uses sodium hydrogencarbonate solution rather than pure water. [1 mark]
(c) Light intensity is inversely proportional to the square of the distance from the lamp. The light intensity at 10 cm is 1.0 arbitrary unit. Calculate the light intensity at 40 cm. [2 marks]
(d) Explain why the rate of photosynthesis falls as the lamp is moved further away. [2 marks]
(e) The student says that counting bubbles is not an accurate way to measure the rate of photosynthesis. Suggest one reason why, and one improvement to the method. [2 marks]
(f) Which variable must be kept the same throughout the investigation? [1 mark]
A the number of bubbles B the distance from the lamp C the temperature of the water D the light intensity
Question 2 — Transport in plants (10 marks)
(a) Describe two differences between the structure of xylem and phloem. [2 marks]
(b) A student uses a potometer to measure the rate of water uptake by a leafy shoot. The air bubble moves 45 mm in 3 minutes. The capillary tube has a cross-sectional area of 0.8 mm².
Calculate the rate of water uptake in mm³ per minute. [3 marks]
(c) A fan is then placed next to the shoot. Explain the effect this has on the rate of transpiration. [2 marks]
(d) Explain how root hair cells are adapted to absorb water and mineral ions from the soil. [3 marks]
Question 3 — Hormones (10 marks)
(a) Which gland releases thyroid-stimulating hormone (TSH)? [1 mark]
A the pancreas B the adrenal gland C the pituitary gland D the thyroid gland
(b) Explain why a hormone released into the blood affects only certain organs. [2 marks]
(c) Describe how negative feedback keeps the level of thyroxine in the blood within a narrow range. [3 marks]
(d) A person has a sudden fright. Describe two effects of adrenaline on the body and explain how each prepares the body for action. [4 marks]
Question 4 — Reproductive hormones and contraception (10 marks)
(a) Name the hormone that causes an egg to be released from the ovary. [1 mark]
(b) Describe the role of oestrogen and progesterone in the menstrual cycle. [3 marks]
*(c) A couple are choosing a method of contraception. Evaluate the use of the combined contraceptive pill compared with condoms. [6 marks]
Question 5 — Blood glucose and diabetes (10 marks)
(a) After a meal, a person's blood glucose concentration rises. Explain how the body returns it to normal. [3 marks]
(b) Explain how glucagon raises blood glucose concentration when it falls too low. [2 marks]
(c) The table shows data for two adults.
| Mass (kg) | Height (m) | Waist (cm) | Hip (cm) | |
|---|---|---|---|---|
| Person X | 90 | 1.80 | 102 | 100 |
| Person Y | 62 | 1.65 | 74 | 96 |
(i) Calculate the BMI of Person X. Use: BMI = mass ÷ height². [2 marks]
(ii) Calculate the waist-to-hip ratio of Person X, to 2 decimal places. [1 mark]
(iii) Use the data to explain which person has the greater risk of developing type 2 diabetes. [2 marks]
Question 6 — Homeostasis: temperature and water (10 marks)
(a) Explain how the body responds when its core temperature rises above 37 °C. [3 marks]
(b) Explain why the body must keep its core temperature close to 37 °C. [2 marks]
(c) After exercise on a hot day, a person produces a small volume of concentrated urine. Explain the role of ADH in this response. [3 marks]
(d) Explain why glucose is normally absent from urine, even though it is filtered out of the blood in the kidney. [2 marks]
Question 7 — Exchange surfaces and transport (10 marks)
(a) A cube-shaped cell has sides of 2 µm. Calculate its surface area to volume ratio. [2 marks]
(b) Explain why large multicellular organisms need specialised exchange surfaces and a transport system. [2 marks]
(c) Explain three ways in which the alveoli are adapted for efficient gas exchange. [3 marks]
(d) Fick's law states that the rate of diffusion is proportional to (surface area × concentration difference) ÷ thickness of membrane. In emphysema, the surface area of the alveoli falls to half of its normal value. Explain the effect on the rate of diffusion of oxygen and on the person. [3 marks]
Question 8 — The heart and respiration (10 marks)
(a) A person has a stroke volume of 75 cm³ and a heart rate of 68 beats per minute. Calculate their cardiac output. Give your answer in dm³ per minute. [2 marks]
(b) In a core practical, a student uses a respirometer containing woodlice and soda lime. The coloured liquid in the capillary tube moves 18 mm in 6 minutes at 20 °C.
(i) Explain why the coloured liquid moves towards the woodlice. [2 marks]
*(ii) The student wants to investigate the effect of temperature on the rate of respiration of woodlice. Describe a method she could use, including how she would make the results valid and act ethically. [6 marks]
Question 9 — Ecosystems and sampling (10 marks)
(a) Which of these is an abiotic factor? [1 mark]
A competition for food B the number of predators C the presence of a pathogen D soil pH
(b) In a core practical, a student estimates the population of daisies on a school field measuring 80 m × 50 m. She places ten 0.25 m² quadrats at random and counts a total of 30 daisies.
(i) Explain why the quadrats are placed at random. [1 mark]
(ii) Calculate the estimated number of daisies on the whole field. [3 marks]
(c) The student then uses a transect from a hedge into the open field. Explain why a transect is more suitable than random quadrats for this investigation. [2 marks]
(d) Grass on the field contains 20 000 kJ of energy. The rabbits that eat it contain 2400 kJ. Calculate the efficiency of energy transfer and explain why it is less than 100%. [3 marks]
Question 10 — Material cycles and human impact (10 marks)
(a) Explain how the nitrogen in a dead leaf is made available again to plants. [2 marks]
(b) In a core practical, a student measures the decomposition of grass cuttings at different temperatures. At 25 °C, 9.6 g of grass loses 2.4 g in mass over 8 days. Calculate the mean rate of decomposition in g per day. [2 marks]
*(c) A farmer spreads large amounts of nitrate fertiliser on fields beside a lake. Explain how this can lead to a fall in biodiversity in the lake, and evaluate two ways of reducing the problem. [6 marks]