Total marks: 100 · Duration: 105 minutes · Tier: Higher
Instructions to candidates
- Use black ink or black ball-point pen. Draw diagrams in pencil.
- Answer all questions in the spaces provided.
- In all calculations, show clearly how you work out your answer.
- You may use a calculator.
- Where a question describes a graph or a diagram in words, you may find it helpful to sketch it.
Information
- The maximum mark for this paper is 100.
- The marks for questions are shown in brackets.
- You are expected to use good English and to organise information clearly, especially in questions marked with an asterisk (*).
- This paper covers AQA GCSE Biology topics 4.5 to 4.7: homeostasis and response; inheritance, variation and evolution; and ecology.
Paper
Question 1 — The nervous system (11 marks)
(a) A person touches a hot plate and pulls their hand away. Describe the pathway of this reflex action, from the stimulus to the response. [4 marks]
(b) Explain how a nerve impulse passes across a synapse. [2 marks]
(c) A student investigates whether practice improves reaction time using the ruler-drop test. A partner drops a ruler and the student catches it as quickly as possible. The distance the ruler falls is converted into a reaction time.
| Attempt | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Reaction time (s) | 0.24 | 0.21 | 0.22 | 0.19 | 0.18 |
(i) Calculate the mean reaction time. [1 mark]
(ii) Give two variables the student should control. [2 marks]
(iii) Suggest why the student's results may not show that practice improves reaction time in general. [2 marks]
Question 2 — The brain and the eye (9 marks)
(a) Name the part of the brain that:
(i) controls unconscious activities such as heart rate and breathing [1 mark]
(ii) coordinates muscle activity and balance. [1 mark]
(b) Explain why it is difficult to treat damage to the brain. [2 marks]
(c) Describe how the eye focuses on a near object. [3 marks]
(d) A person is short-sighted (has myopia). Describe the cause of short-sightedness and how it can be corrected with spectacle lenses. [2 marks]
Question 3 — Control of blood glucose (12 marks)
(a) Describe how the body returns the blood glucose concentration to normal after a meal containing a lot of carbohydrate. [3 marks]
(b) Explain how the body responds when the blood glucose concentration falls too low. [3 marks]
(c) Compare the causes and the treatments of Type 1 and Type 2 diabetes. [4 marks]
(d) Thyroxine stimulates the basal metabolic rate. Its level in the blood is controlled by negative feedback. Explain what is meant by negative feedback. [2 marks]
Question 4 — Water balance and the kidney (10 marks)
(a) Explain how the body responds when the water concentration of the blood is too low. [3 marks]
(b) Name the waste product formed in the liver from the breakdown of excess amino acids. [1 mark]
(c)* People with kidney failure can be treated by kidney dialysis or by a kidney transplant.
Evaluate these two treatments. [6 marks]
Question 5 — Reproduction and hormones (11 marks)
(a) Name the hormone that stimulates the release of an egg (ovulation). [1 mark]
(b) Describe the roles of oestrogen and progesterone in the menstrual cycle. [2 marks]
(c) Give one advantage and one disadvantage of using the contraceptive pill compared with a condom. [2 marks]
(d) Describe how IVF treatment is carried out. [3 marks]
(e) Give three differences between meiosis and mitosis. [3 marks]
Question 6 — Genetics and inheritance (12 marks)
Cystic fibrosis is an inherited disorder caused by a recessive allele (f). The dominant allele is F.
(a) Two parents do not have cystic fibrosis, but both are carriers.
(i) Give the genotype of each parent. [1 mark]
(ii) Draw a Punnett square for a cross between the two parents. [2 marks]
(iii) Give the probability that their first child will have cystic fibrosis. [1 mark]
(iv) Give the probability that their first child will be a carrier. [1 mark]
(b) Polydactyly is caused by a dominant allele. Explain why a person with only one copy of this allele has polydactyly. [1 mark]
(c) Embryos can be screened for cystic fibrosis before they are implanted during IVF. Give one argument for and one argument against embryo screening. [2 marks]
(d) Explain how the sex of a child is determined, and why there is an equal chance of a boy or a girl. [2 marks]
(e) DNA is a polymer made of repeating units. Name these units. [1 mark]
(f) What is meant by the genome of an organism? [1 mark]
Question 7 — Variation and evolution (11 marks)
(a)* Some strains of bacteria have become resistant to antibiotics.
Explain how antibiotic-resistant bacteria evolve by natural selection, and why resistant strains spread. [6 marks]
(b) Describe how farmers use selective breeding to produce cattle with a high milk yield. [3 marks]
(c) Give one benefit and one concern about growing genetically modified crops. [2 marks]
Question 8 — Ecosystems and sampling (12 marks)
(a) A student estimates the number of daisies in a field measuring 30 m by 20 m. She places 10 quadrats, each with an area of 0.25 m², at random positions. The mean number of daisies per quadrat is 3.2.
(i) Calculate the estimated number of daisies in the field. [3 marks]
(ii) Describe how the student could place the quadrats at random. [1 mark]
(iii) Suggest how the student could make the estimate more accurate. [1 mark]
(b) Describe how a transect could be used to investigate how the distribution of daisies changes from the shade of a tree into the open field. [3 marks]
(c) Give two abiotic factors that could affect the distribution of daisies. [2 marks]
(d) In a stable community, the numbers of a predator and its prey rise and fall in cycles. Explain why the predator population peaks after the prey population. [2 marks]
Question 9 — Biomass, cycles and biodiversity (12 marks)
(a) The table shows the biomass at each trophic level in a food chain.
| Trophic level | Producers | Primary consumers | Secondary consumers |
|---|---|---|---|
| Biomass (g/m²) | 8000 | 640 | 48 |
(i) Calculate the efficiency of biomass transfer from primary consumers to secondary consumers. [2 marks]
(ii) Give two reasons why biomass is lost between trophic levels. [2 marks]
(b) Describe how carbon is returned to the atmosphere in the carbon cycle. [3 marks]
(c) Explain why decay is faster in warm, moist conditions than in cold, dry conditions. [2 marks]
(d) Give two ways of maintaining biodiversity. [2 marks]
(e) What is meant by food security? [1 mark]