Edexcel GCSE·🧬 Biology·higher

Edexcel GCSE Biology — Paper 1 (Higher Tier)

⏱ 105 minutes📊 100 marks📄 Paper 1 (Higher Tier)

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ℹ️ About this paper: This is an exam-board-aligned practice paper written in the style of Edexcel GCSE — not an official past paper. Use it for timed practice, then check against the mark scheme included below. For official past papers, see the exam board's website.

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Edexcel GCSE Biology — Paper 1 (Higher Tier)

Total marks: 100 · Duration: 105 minutes · Tier: Higher

Instructions to candidates

• Answer ALL questions in both Section A and Section B. • Write your answers in the spaces provided in this question paper. • You may use a calculator. • You should show all your working in calculation questions. • The marks allocated for each question are shown in brackets after the question. • Section A contains structured questions worth 60 marks in total. • Section B contains extended response questions worth 40 marks in total.

Paper

Section A — Structured Questions (60 marks)

Question 1

A student investigated the effect of pH on the activity of the enzyme amylase. Amylase catalyses the breakdown of starch into maltose.

The student: • placed 2 cm³ of starch solution into five test tubes • added 2 cm³ of buffer solution at different pH values (pH 4, 5, 6, 7, 8) to each test tube • added 1 cm³ of amylase solution to each test tube and started a timer • recorded the time taken for all the starch to be broken down at each pH • repeated the experiment twice and calculated a mean time

The results are shown in Table 1.

Table 1

pH	Time taken for starch to be broken down (seconds)			Mean time (seconds)
	Trial 1	Trial 2	Trial 3
4	184	176	180	180
5	98	102	94	98
6	45	42	48	45
7	52	56	52	53
8	112	124	120	119

(a) Describe how the student could test for the presence of starch in the test tubes. (2 marks)

(b) State two variables the student should control in this investigation. (2 marks)

(c) Calculate the rate of reaction at pH 6. Give your answer to 3 significant figures.

Use the equation:

rate of reaction = 1 / time

(2 marks)

(d) The student concluded that the optimum pH for amylase activity is pH 6.

Evaluate this conclusion using the data in Table 1. (3 marks)

(e) Explain why the rate of reaction is lower at pH 4 compared to pH 6. (3 marks)

[Total for Question 1: 12 marks]

Question 2

Figure 1 shows a section through the human heart.

[Figure 1 shows a diagram of the heart with structures labelled A, B, C and D. Structure A is the aorta, B is the left ventricle, C is the left atrium, and D is a valve between the left atrium and left ventricle]

(a) Name the structures labelled A and D in Figure 1. (2 marks)

(b) Explain why the wall of structure B is thicker than the wall of structure C. (2 marks)

(c) Blood flows through the heart in one direction only.

Explain how structure D prevents backflow of blood. (2 marks)

(d) Coronary heart disease occurs when fatty deposits build up in the coronary arteries, reducing blood flow to the heart muscle.

A patient with coronary heart disease may be fitted with a stent.

Describe how a stent treats coronary heart disease. (2 marks)

(e) Some patients with coronary heart disease are given statins instead of, or as well as, having a stent fitted.

Statins are drugs that reduce blood cholesterol levels.

Discuss the advantages and disadvantages of using statins to treat coronary heart disease. (4 marks)

[Total for Question 2: 12 marks]

Question 3

Cystic fibrosis is a genetic disorder caused by a recessive allele. The disorder affects the cell membranes that produce mucus, sweat and digestive juices.

Figure 2 shows a family pedigree for cystic fibrosis.

[Figure 2 shows a family pedigree with:

Generation 1: Male (unaffected) and Female (unaffected) parents
Generation 2: Three children - Male (affected with cystic fibrosis), Female (unaffected), Male (unaffected)
Generation 3: The unaffected female from Generation 2 has two children with an unaffected male - Female (unaffected) and Male (affected with cystic fibrosis)]

Key: □ = unaffected male ○ = unaffected female ■ = affected male ● = affected female

(a) Use evidence from Figure 2 to explain how you know that cystic fibrosis is caused by a recessive allele. (2 marks)

(b) The unaffected female in Generation 2 is a carrier of the cystic fibrosis allele.

Let F represent the dominant allele and f represent the recessive allele.

Complete the genetic diagram to show how this female could have a child affected by cystic fibrosis.

Parental phenotypes: carrier female × ______________________

Parental genotypes: Ff × ______________________

Gametes: ______________________ × ______________________

Offspring genotypes: ______________________

Offspring phenotypes: ______________________

(4 marks)

(c) Use your genetic diagram to calculate the probability that this couple's next child will be affected by cystic fibrosis.

Give your answer as a percentage. (1 mark)

(d) People with cystic fibrosis produce thick, sticky mucus in their airways.

Suggest why people with cystic fibrosis have an increased risk of lung infections. (2 marks)

(e) Scientists are developing gene therapy treatments for cystic fibrosis.

Gene therapy involves inserting a working copy of the gene into a person's lung cells.

Suggest one reason why gene therapy for cystic fibrosis is difficult to develop. (1 mark)

[Total for Question 3: 10 marks]

Question 4

A student investigated osmosis using potato cylinders.

The student: • cut five potato cylinders of equal length and diameter using a cork borer • measured and recorded the mass of each cylinder • placed each cylinder in a different concentration of sugar solution (0%, 0.25%, 0.50%, 0.75%, 1.00%) • left the cylinders in the solutions for 24 hours • removed the cylinders, blotted them dry with paper towels, and measured their mass again • calculated the percentage change in mass for each cylinder

The results are shown in Table 2.

Table 2

Sugar concentration (%)	Initial mass (g)	Final mass (g)	Change in mass (g)	Percentage change in mass (%)
0	2.45	2.76	+0.31	+12.7
0.25	2.38	2.52	+0.14	+5.9
0.50	2.41	2.41	0	0
0.75	2.46	2.32	−0.14	−5.7
1.00	2.40	2.16	−0.24	−10.0

(a) Describe the relationship between sugar concentration and percentage change in mass shown in Table 2. (2 marks)

(b) Explain why the potato cylinder in 0% sugar solution (distilled water) increased in mass. (3 marks)

(c) Use the results in Table 2 to estimate the concentration of sugar solution inside the potato cells.

Explain your answer. (2 marks)

(d) The student blotted the potato cylinders dry with paper towels before measuring their final mass.

Explain why this was important. (1 mark)

(e) Another student suggested repeating the experiment using potato cylinders of different lengths.

Explain why using potato cylinders of different lengths would make the investigation less valid. (2 marks)

[Total for Question 4: 10 marks]

Question 5

Bacteria can reproduce very rapidly by binary fission when conditions are favourable.

Figure 3 shows how the number of bacteria in a culture changed over 8 hours.

[Figure 3 shows a graph with:

X-axis: Time (hours) from 0 to 8
Y-axis: Number of bacteria (thousands) from 0 to 500
The curve shows: slow increase 0-1h, rapid exponential increase 1-5h, leveling off 5-8h at around 480 thousand]

(a) Calculate the number of times the bacteria divided between 1 hour and 3 hours.

Show your working. (3 marks)

(b) Describe and explain the shape of the graph between 5 and 8 hours. (3 marks)

(c) A scientist added an antibiotic to a bacterial culture.

The antibiotic inhibits enzymes involved in bacterial cell wall synthesis.

Explain how this antibiotic kills bacteria. (2 marks)

(d) Some bacteria have developed resistance to antibiotics.

Explain how antibiotic resistance in bacteria is an example of evolution by natural selection. (4 marks)

[Total for Question 5: 12 marks]

Question 6

Plants produce glucose by photosynthesis. Glucose can be converted into other substances.

(a) Write the balanced symbol equation for photosynthesis. (2 marks)

(b) Name the two products formed when glucose molecules are joined together in plant cells. (2 marks)

(c) Figure 4 shows the absorption spectrum for chlorophyll a and chlorophyll b.

[Figure 4 shows a graph with:

X-axis: Wavelength of light (nm) from 400 to 700
Y-axis: Absorption (arbitrary units)
Chlorophyll a shows peaks at approximately 430nm and 660nm
Chlorophyll b shows peaks at approximately 450nm and 640nm
Both show low absorption between 500-600nm (green light)]

Use Figure 4 to explain why most leaves appear green. (2 marks)

(d) A farmer wants to increase the rate of photosynthesis in tomato plants growing in a greenhouse.

Suggest and explain two ways the farmer could increase the rate of photosynthesis. (4 marks)

[Total for Question 6: 10 marks]

Section B — Extended Response (40 marks)

Question 7

Cancer is a non-communicable disease caused by uncontrolled cell division. There are many different types of cancer, and several risk factors have been identified.

Table 3 shows data about the incidence of lung cancer in the UK.

Table 3

Factor	Incidence of lung cancer (cases per 100,000 people per year)
Non-smokers	8
Smokers (1-14 cigarettes per day)	78
Smokers (15-24 cigarettes per day)	127
Smokers (25+ cigarettes per day)	251
People exposed to radon gas	42
People exposed to asbestos	65

Radon is a radioactive gas that occurs naturally in some rocks. Asbestos is a material that was previously used in building construction.

Evaluate the evidence in Table 3 for smoking being the most important risk factor for lung cancer. (9 marks)

[Total for Question 7: 9 marks]

Question 8

The human body has several mechanisms for defending against pathogens.

These include: • physical and chemical barriers that prevent pathogens entering the body • the immune system that destroys pathogens that enter the body • vaccination programmes that provide immunity against specific diseases

(a) Discuss how the human body defends itself against pathogens.

You should include: • examples of physical and chemical barriers • how white blood cells destroy pathogens • how vaccination provides immunity

(9 marks)

(b) Scientists are developing new treatments for bacterial infections because antibiotic resistance is increasing.

One approach being investigated is the use of bacteriophages. Bacteriophages are viruses that infect and kill bacteria but do not infect human cells.

Evaluate the use of bacteriophages as an alternative to antibiotics for treating bacterial infections. (6 marks)

[Total for Question 8: 15 marks]

Question 9

Ecosystems consist of all the living organisms in a habitat and their physical environment. Organisms in an ecosystem depend on each other for resources such as food and shelter.

Human activities can affect ecosystems. For example: • deforestation removes large areas of forest to provide land for agriculture or timber • pollution from factories and vehicles releases toxic substances into the environment • introduction of non-native species can disrupt food chains and competition

A nature reserve manager wants to maintain biodiversity in a woodland ecosystem that is threatened by nearby urban development.

Assess the impact of human activities on ecosystems and discuss strategies that could be used to maintain biodiversity in the woodland. (10 marks)

[Total for Question 9: 10 marks]

Question 10

The kidneys play an important role in homeostasis by regulating the water and ion content of the blood.

Figure 5 shows a nephron, the functional unit of the kidney.

[Figure 5 shows a labelled diagram of a nephron including: glomerulus, Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct. Arrows show blood entering via afferent arteriole and leaving via efferent arteriole.]

Describe and explain how the nephron produces urine.

In your answer you should: • describe the processes of filtration and selective reabsorption • explain how the structure of the nephron is adapted for these processes • explain the role of ADH in regulating water content

(6 marks)

[Total for Question 10: 6 marks]

END OF PAPER

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Mark Scheme

Section A — Structured Questions (60 marks)

Question 1

(a) (2 marks)

Award 1 mark for each of the following, up to 2 marks: • Add iodine (solution) to the test tube / to a sample from the test tube (1) • If starch is present, the solution turns blue-black / dark blue (1)

Accept: 'Add iodine and it will turn blue-black if starch is there' Reject: 'Add iodine' alone without result

(b) (2 marks)

Award 1 mark for each controlled variable identified, up to 2 marks: • Temperature (of the solutions) (1) • Volume of starch solution (1) • Volume of amylase solution (1) • Concentration of starch solution (1) • Concentration of amylase solution (1) • Source of amylase (1)

Accept any two valid controlled variables Reject: pH (this is the independent variable)

(c) (2 marks)

Award marks as follows: • Correct substitution: rate = 1/45 (1) • Correct answer: 0.0222 s⁻¹ (1)

Accept: 0.022 s⁻¹ or 2.22 × 10⁻² s⁻¹ Accept answers showing 3 significant figures Reject answers not to 3 significant figures if question specifies this

(d) (3 marks)

Indicative content: • The conclusion is supported because pH 6 has the shortest/fastest time (1) • pH 6 shows the highest rate of reaction / fastest breakdown of starch (1) • However, pH values between 5 and 7 were not tested / only whole number pH values tested (1) • So the optimum pH might be between 6 and 7 / more pH values should be tested (1) • The differences between pH 6 and pH 7 are relatively small (1)

Award 3 marks for a full evaluation including support and limitation(s) Award 2 marks for partial evaluation Award 1 mark for simple statement

(e) (3 marks)

Award 1 mark for each of the following, up to 3 marks: • At pH 4, the pH is more acidic / further from optimum (1) • The active site of the enzyme changes shape / enzyme denatures / enzyme structure is altered (1) • The substrate no longer fits the active site / enzyme-substrate complexes cannot form (1) • So fewer substrate molecules are broken down (per unit time) (1)

Award maximum 3 marks Accept: 'bonds in enzyme break' for denaturation Reject: 'enzyme dies' or 'enzyme killed'

Question 2

(a) (2 marks)

Award 1 mark for each correct identification: • A = aorta (1) • D = valve / bicuspid valve / mitral valve / atrioventricular valve (1)

Reject: 'vein' for aorta Accept: 'heart valve' or 'AV valve' for D

(b) (2 marks)

Award marks as follows: • The left ventricle has to pump blood further / around the body / to the body (1) • (So) needs to generate higher pressure / more force / stronger contractions (1)

Accept: 'left ventricle pumps blood to body, left atrium only pumps to ventricle' Reject: 'pumps more blood' alone

(c) (2 marks)

Award marks as follows: • The valve opens when the atrium contracts / when pressure in atrium is higher (1) • The valve closes when the ventricle contracts / when pressure in ventricle is higher / when blood tries to flow backwards (1)

Accept: description of pressure differences causing valve movement Accept: 'tendons/cords hold valve in place' Reject: 'valve seals the entrance' without mechanism

(d) (2 marks)

Award marks as follows: • A stent is inserted into the coronary artery (1) • It keeps the artery open / holds the artery walls apart / maintains blood flow (to the heart muscle) (1)

Accept: 'metal mesh/tube inserted into artery' Accept: 'prevents artery from narrowing' Reject: 'removes blockage' (stents don't remove fatty deposits)

(e) (4 marks)

Indicative content:

Advantages: • Reduces cholesterol levels / reduces risk of fatty deposits forming (1) • Reduces risk of heart attack / stroke / coronary heart disease (1) • Non-invasive / no surgery required (1) • Can be used with other treatments / alongside stents (1)

Disadvantages: • Must be taken regularly / long-term / daily (1) • Side effects (e.g., muscle pain, liver problems, memory problems) (1) • Cost of long-term medication (1) • May not work for all patients / effectiveness varies (1) • Doesn't address existing blockages, only prevents new ones (1)

Award marks for advantages and disadvantages identified and explained Maximum 4 marks total Credit any valid advantage or disadvantage

Question 3

(a) (2 marks)

Award marks as follows: • Two unaffected parents can have an affected child / the parents in generation 1 are unaffected but have an affected son (1) • This shows both parents must be carriers / both parents must have one copy of the recessive allele (1)

Accept: reference to specific individuals in the pedigree Reject: 'it skips a generation' alone without explanation

(b) (4 marks)

Award marks as follows:

Parental phenotypes: • Unaffected male / carrier male / normal male (1)

Parental genotypes: • Ff (1)

Gametes: • F and f × F and f (1)

Offspring genotypes: • FF, Ff, Ff, ff / 1 FF : 2 Ff : 1 ff (1)

Accept genetic diagrams shown as Punnett squares Accept alternative correct notation (e.g., N and n) Award marks for each correct component

Offspring phenotypes: • 3 unaffected : 1 affected / 3 normal : 1 cystic fibrosis (allow if included) (Mark scheme allows this but marks already allocated above)

(c) (1 mark)

Award mark for: • 25% / 1 in 4 / 0.25 (1)

Accept: '25 percent' or '25' Reject: '1 in 4' if question asks specifically for percentage Accept: ¼ if conversion shown

(d) (2 marks)

Award marks as follows: • Thick mucus traps bacteria / pathogens / microorganisms (1) • Mucus cannot be cleared / cilia cannot move mucus / bacteria are not removed from airways (1) • (So) bacteria can multiply / bacteria remain in lungs (1)

Maximum 2 marks Accept: 'mucus blocks airways allowing bacteria to grow'

(e) (1 mark)

Award 1 mark for any of the following: • Difficult to get the gene into all lung cells / lung cells (1) • Lung cells are constantly replaced / new cells don't have the gene (1) • Immune system may attack the vector / virus used to deliver gene (1) • Effect is temporary / treatment needs to be repeated (1)

Accept any valid difficulty Accept: 'hard to deliver gene to target cells'

Question 4

(a) (2 marks)

Award marks as follows: • As sugar concentration increases, percentage change in mass decreases / becomes more negative (1) • Relationship is negative correlation / inverse relationship (1)

Accept: 'the higher the sugar concentration, the more mass is lost' Accept: description of the pattern in words Reject: 'they are inversely proportional' (not proportional)

(b) (3 marks)

Award 1 mark for each of the following, up to 3 marks: • Water moves into the potato cells / into the potato cylinder (1) • By osmosis (1) • From a dilute solution / from high water potential / from high water concentration to a more concentrated solution / to lower water potential / to lower water concentration (1) • Through a partially permeable membrane / through the cell membrane (1) • Because water concentration in the potato cells is lower than in distilled water / water potential in cells is lower than outside (1)

Award maximum 3 marks Must include 'osmosis' for full marks Accept: 'from high to low concentration' if context indicates water

(c) (2 marks)

Award marks as follows: • 0.50% / 0.5% (1) • Because there is no change in mass / this is where the sugar concentration inside cells equals outside / this is the isotonic point (1)

Accept: 'around 0.5%' or 'between 0.25% and 0.75%' Reject: answer without explanation

(d) (1 mark)

Award mark for: • To remove water from the outside / surface of the cylinder (1) • So only water inside the cylinder is measured / to make measurements accurate (1)

Accept either point for 1 mark

(e) (2 marks)

Award marks as follows: • Length affects surface area (to volume ratio) (1) • Different surface areas would mean different rates of osmosis / different amounts of water gain/loss (1) • (So) results would not be comparable / would introduce another variable (1)

Maximum 2 marks Accept: 'surface area affects rate of osmosis'

Question 5

(a) (3 marks)

Award marks as follows: • At 1 hour, number of bacteria ≈ 10 (thousand) / 10,000 (1) • At 3 hours, number of bacteria ≈ 80 (thousand) / 80,000 (1) • Number of times divided = 3 (1)

Working: 10 → 20 → 40 → 80 (three divisions) or 80/10 = 8, and 2³ = 8, so 3 divisions

Accept: clear working showing understanding of binary fission Accept: ±5 thousand in readings from graph Must show method for full marks

(b) (3 marks)

Award 1 mark for each of the following, up to 3 marks: • The graph levels off / rate of increase slows / reaches plateau / stationary phase (1) • Because nutrients/food are used up / waste products accumulate (1) • Because space/resources become limited (1) • (So) rate of reproduction decreases / rate of reproduction = rate of death (1)

Maximum 3 marks Must describe the pattern (1 mark) and provide explanation (up to 2 marks)

(c) (2 marks)

Award marks as follows: • The cell wall cannot be synthesized / formed / made / built (1) • The cell bursts / lyses / cannot maintain shape / water enters by osmosis causing cell to burst (1)

Accept: 'without cell wall, cell membrane cannot withstand pressure' Accept: 'cell wall provides structural support' Reject: 'cell wall is destroyed' (antibiotic prevents synthesis, doesn't destroy)

(d) (4 marks)

Award 1 mark for each of the following, up to 4 marks: • Variation exists / some bacteria have mutations (1) • Some bacteria have alleles / genes that make them resistant to antibiotics (1) • When antibiotics are used, non-resistant bacteria die / are killed (1) • Resistant bacteria survive and reproduce (1) • The allele for resistance is passed to offspring (1) • Over time, the proportion of resistant bacteria increases / resistant bacteria become more common (1)

Maximum 4 marks Must include: variation, selection pressure, survival of resistant, reproduction Accept: 'natural selection' or 'survival of the fittest' if explained

Question 6

(a) (2 marks)

Award marks as follows: • 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (2)

Award 2 marks for fully correct balanced equation with state symbols not required Award 1 mark for correct equation with minor error (e.g., not balanced, missing numbers)

Accept: carbon dioxide + water → glucose + oxygen (1 mark only) Reject: equation with incorrect balancing

(b) (2 marks)

Award 1 mark for each of the following: • Starch (1) • Cellulose (1)

Reject: 'carbohydrate' (too vague) Accept: 'cell wall' if clearly referring to cellulose

(c) (2 marks)

Award marks as follows: • Chlorophyll absorbs red and blue light / light at 430nm, 450nm, 640nm, 660nm (1) • Chlorophyll does not absorb green light / green light is reflected / transmitted (1)

Accept: reference to wavelengths from graph Accept: 'low absorption between 500-600nm' Reject: 'chlorophyll is green' without explanation

(d) (4 marks)

Award 1 mark for each suggestion and 1 mark for explanation (2 marks per factor, maximum 4 marks):

Possible answers: • Increase light intensity / add artificial lights (1)

More energy for photosynthesis / light is used in photosynthesis (1)

• Increase carbon dioxide concentration / add CO₂ (1)

Carbon dioxide is a raw material / reactant for photosynthesis (1)

• Increase temperature / add heating (1)

Enzymes work faster / increases rate of enzyme activity (1)
But not too high or enzymes denature (accept if stated)

Accept: any two valid factors with explanations Reject: 'water' alone (plants unlikely to be limited by water in greenhouse) Maximum 4 marks (2 factors with explanations)

Section B — Extended Response (40 marks)

Question 7 (9 marks)

Level 3 (7-9 marks): A detailed evaluation that analyses the data in Table 3 and makes a justified conclusion about whether smoking is the most important risk factor. Makes comparisons between different risk factors using specific data. Considers limitations of the data and/or other factors that might affect lung cancer risk. Answer is coherent, logically structured and uses scientific terminology accurately.

Level 2 (4-6 marks): An evaluation that describes the relationship between smoking and lung cancer using data from the table. Makes some comparison with other risk factors. May identify some limitations but these are not fully developed. Answer has some logical structure and uses scientific terminology appropriately.

Level 1 (1-3 marks): Basic statements about the data with limited evaluation. May simply describe data without comparison. Limited or no use of data to support statements. Answer lacks coherent structure and uses limited scientific terminology.

0 marks: No relevant content.

Indicative content:

Support for smoking being most important:

Smokers have much higher incidence than non-smokers (78-251 vs 8 per 100,000)
Clear dose-response relationship: more cigarettes = higher incidence (78 → 127 → 251)
Heavy smokers (25+/day) have highest incidence of all groups (251)
Difference between non-smokers and lightest smokers is large (8 → 78, almost 10× increase)
Smokers have higher incidence than people exposed to radon (251 vs 42) or asbestos (251 vs 65)

Evidence against/limitations:

Radon and asbestos also increase risk significantly compared to baseline (42 and 65 vs 8)
Data doesn't show combined effects (e.g., smoking + radon exposure)
No information about exposure duration/dose for radon and asbestos
Other risk factors not shown in table (e.g., genetics, air pollution, diet)
Incidence data doesn't show causation directly
No information about sample size or uncertainty in data
Individual variation not shown

Conclusion:

Evaluation of whether data supports smoking as "most important"
Consideration that "most important" could mean different things (highest risk, most preventable, affects most people)

Question 8(a) (9 marks)

Level 3 (7-9 marks): A comprehensive discussion covering all three bullet points with detailed explanations of mechanisms. Provides specific examples of barriers, describes how white blood cells destroy pathogens using multiple methods, and explains the immune response to vaccination clearly. Answer is well-organized, coherent and uses scientific terminology accurately throughout.

Level 2 (4-6 marks): A discussion covering at least two of the three bullet points with some detail. Provides some examples and describes some mechanisms but may lack detail or precision. Some explanation of how defenses work. Answer has reasonable structure and uses scientific terminology appropriately.

Level 1 (1-3 marks): Basic statements about body defenses with limited detail. May list defenses without explaining how they work. Covers only one bullet point in detail or multiple points superficially. Limited coherent structure and use of scientific terminology.

0 marks: No relevant content.

Indicative content:

Physical and chemical barriers:

Skin: acts as physical barrier / prevents entry of pathogens
Skin produces antimicrobial secretions / sebum
Nose: hairs and mucus trap pathogens
Trachea and bronchi: ciliated epithelial cells waft mucus (containing trapped pathogens) upward
Stomach: produces hydrochloric acid / low pH kills pathogens
Eyes: produce tears containing lysozyme (enzyme that kills bacteria)

How white blood cells destroy pathogens:

Phagocytosis: white blood cells engulf and digest pathogens
Producing antibodies: specific proteins that bind to antigens on pathogen surface
Antibodies cause pathogens to clump together / be destroyed / be marked for phagocytosis
Producing antitoxins: neutralize toxins produced by bacteria
Lymphocytes recognize specific antigens
Memory cells remain in blood after infection

Vaccination:

Vaccination introduces dead/inactive pathogen or antigen
White blood cells produce antibodies specific to the pathogen
Memory cells are produced
If live pathogen enters body later, memory cells recognize it
Antibodies produced rapidly / in large quantities
Secondary immune response is faster and stronger
Pathogen is destroyed before symptoms develop / person becomes immune

Question 8(b) (6 marks)

Level 3 (5-6 marks): A detailed evaluation considering both advantages and disadvantages of using bacteriophages as an alternative to antibiotics. Makes reasoned judgements about the potential of this treatment. Uses scientific knowledge to support the evaluation. Answer is coherent and logically structured.

Level 2 (3-4 marks): An evaluation identifying some advantages and disadvantages. Some development of points but may lack balance or detail. Some scientific reasoning. Answer has some logical structure.

Level 1 (1-2 marks): Basic statements about bacteriophages with limited evaluation. May simply list advantages or disadvantages without development. Limited scientific reasoning.

0 marks: No relevant content.

Indicative content:

Advantages:

Specific to bacteria / don't harm human cells / fewer side effects
Target specific bacterial species / can be targeted at pathogen
Don't kill beneficial bacteria (e.g., gut bacteria)
Can work against antibiotic-resistant bacteria
Bacteriophages evolve alongside bacteria / can overcome resistance
Naturally occurring / found in environment
Self-replicating: multiply at site of infection

Disadvantages:

Very specific / need to identify bacterial species first / takes time
May need different bacteriophages for different infections
Limited research / long-term effects unknown
Not yet licensed/approved for widespread use in many countries
Immune system might destroy bacteriophages
Public may be concerned about using viruses as treatment
May be expensive to develop/produce
Bacteria could evolve resistance to bacteriophages too
Bacteriophages might cause release of toxins when bacteria burst

Conclusion/evaluation:

Could be useful alternative where antibiotics fail
Need more research before widespread use
Might be used in combination with antibiotics

Question 9 (10 marks)

Level 3 (8-10 marks): A comprehensive answer that assesses multiple human impacts on ecosystems with specific examples, and discusses detailed strategies for maintaining biodiversity. Shows clear understanding of ecological concepts. Makes reasoned judgements about the effectiveness of strategies. Answer is well-organized, coherent and uses scientific terminology accurately throughout.

Level 2 (5-7 marks): Describes several human impacts and suggests some strategies for maintaining biodiversity. Shows understanding of some ecological concepts. Some development of ideas but may lack detail or specific examples. Answer has reasonable structure and uses scientific terminology appropriately.

Level 1 (1-4 marks): Basic statements about human impacts and/or conservation strategies with limited detail. May simply list impacts or strategies without explanation. Limited understanding of ecological concepts. Limited coherent structure and use of scientific terminology.

0 marks: No relevant content.

Indicative content:

Impact of human activities:

Deforestation:

Loss of habitat for species / destruction of food chains
Reduces biodiversity / species become extinct
Loss of trees reduces carbon dioxide absorption / increases greenhouse gases
Soil erosion occurs
Disrupts nutrient cycling

Pollution:

Toxic substances kill organisms / reduce populations
Air pollution affects plants (e.g., acid rain damages leaves)
Water pollution affects aquatic organisms
Bioaccumulation of toxins through food chains
Eutrophication from fertilizer runoff

Non-native species:

Compete with native species for resources
May have no natural predators / outcompete native species
Disrupt food chains / webs
May bring new diseases
Can cause extinction of native species

Urban development:

Habitat loss / fragmentation
Reduces available space for species
Light and noise pollution affects behavior
Interrupts migration routes / movement of species

Strategies to maintain biodiversity:

Protection:

Create nature reserves / protected areas
Legal protection for endangered species
Restrict access to sensitive areas
Control activities allowed in woodland

Habitat management:

Maintain variety of habitats (e.g., clearings, dense woodland)
Coppicing / sustainable woodland management
Create wildlife corridors linking habitats
Control invasive species
Plant native species
Create buffer zones around reserve

Monitoring:

Regular surveys of species populations
Monitor habitat quality
Identify threats early
Use data to inform management decisions

Education and engagement:

Educate public about importance of biodiversity
Involve local community in conservation
Promote sustainable use of resources
Encourage visitors to follow codes of conduct

Specific to urban development threat:

Negotiate with developers for sustainable development
Require environmental impact assessments
Create green spaces in development
Enforce planning restrictions

Evaluation:

Some strategies more effective than others
Need combination of approaches
Requires funding and long-term commitment
Need cooperation from multiple stakeholders
Balance conservation with human needs

Question 10 (6 marks)

Level 3 (5-6 marks): A detailed description and explanation covering all three bullet points. Clearly explains filtration in the glomerulus, selective reabsorption in the tubules, and the role of ADH. Links structure to function. Uses scientific terminology accurately. Answer is coherent and logically structured.

Level 2 (3-4 marks): Describes and explains at least two of the three bullet points with some detail. Some links between structure and function. Uses scientific terminology appropriately. Answer has some logical structure.

Level 1 (1-2 marks): Basic description of one or two processes with limited explanation. May not link structure to function. Limited use of scientific terminology. Answer lacks coherent structure.

0 marks: No relevant content.

Indicative content:

Filtration:

Blood enters glomerulus under high pressure
Small molecules filtered from blood into Bowman's capsule
Filter includes: water, glucose, urea, ions/salts
Large molecules (proteins, blood cells) cannot pass through / remain in blood
Filtrate moves into tubule
High pressure created by: narrow efferent arteriole / afferent arteriole wider than efferent

Selective reabsorption:

Useful substances reabsorbed from tubule back into blood
All glucose reabsorbed (proximal tubule)
Some water reabsorbed
Some ions reabsorbed
Urea not reabsorbed (waste product)
Reabsorption by: diffusion, osmosis, active transport

Structure-function adaptations:

Tubule has large surface area for reabsorption
Tubule has many mitochondria to provide energy for active transport
Tubule cells have microvilli to increase surface area
Close association between tubule and capillaries / blood vessels
Glomerulus has many capillaries to increase surface area for filtration
Bowman's capsule surrounds glomerulus to collect filtrate

Role of ADH:

ADH is a hormone released by pituitary gland
Controls water reabsorption in collecting duct
When body is dehydrated / water content low:
- More ADH released
- Collecting duct becomes more permeable to water
- More water reabsorbed
- Urine more concentrated / smaller volume
When body has excess water:
- Less ADH released
- Collecting duct less permeable to water
- Less water reabsorbed
- Urine dilute / larger volume
This is negative feedback / homeostatic control

Formation of urine:

Filtrate remaining in tubule passes to bladder as urine
Urine contains: water, urea, ions
Composition varies depending on body's needs

Sample Answers with Examiner Commentary

Question 7 — Sample Answers

Grade 9 (top of Higher) answer

The data in Table 3 provides strong evidence that smoking is the most important risk factor for lung cancer. The incidence rate increases dramatically with smoking, from just 8 cases per 100,000 in non-smokers to 78 in light smokers, and reaches 251 in heavy smokers. This represents over a 30-fold increase, which is substantially higher than the increases seen with radon exposure (42 per 100,000) or asbestos exposure (65 per 100,000). Furthermore, there is a clear dose-response relationship: as the number of cigarettes smoked per day increases, so does the incidence of lung cancer (78 → 127 → 251). This pattern strongly suggests a causal relationship rather than just correlation.

However, there are limitations to concluding that smoking is definitively "the most important" risk factor. First, the data doesn't account for people who might be exposed to multiple risk factors simultaneously. For example, a smoker who also works with asbestos or lives in a radon-affected area would likely have an even higher risk than shown in the table. Second, the term "most important" could be interpreted in different ways. While smoking causes the highest incidence in the exposed population, other factors like genetic predisposition or air pollution are not shown in this data and might be significant. Third, the data for radon and asbestos doesn't specify the level or duration of exposure, making direct comparison difficult. Someone with very high asbestos exposure over many years might have a risk comparable to heavy smokers.

From a public health perspective, smoking could still be considered "most important" because it is the most preventable and affects the largest number of people in the population. The data shows that even light smoking causes a substantial increase in risk, and smoking is a voluntary behavior that can be changed through public health interventions. Overall, while the data provides strong evidence that smoking is a major risk factor causing the highest incidence rates among those shown, it would be more accurate to say smoking is "one of the most important" risk factors rather than absolutely "the most important," as other factors and combinations of factors are not fully represented in this limited dataset.

Mark: 9/9

Examiner commentary: This is an exemplary response that demonstrates Level 3 assessment skills throughout. The candidate uses specific data from the table to support arguments (quotes actual figures and calculates the 30-fold increase), identifies the dose-response relationship, and distinguishes between correlation and causation. The answer considers multiple interpretations of "most important" and evaluates limitations of the dataset, including the lack of information about combined exposures and exposure levels. The response is logically structured, moving from evidence supporting the statement, to limitations, to a nuanced conclusion that appropriately qualifies the claim. Scientific terminology is used accurately throughout. This achieves full marks across all assessment criteria.

Grade 6 (solid pass) answer

The data shows that smoking is an important risk factor for lung cancer. Non-smokers only have 8 cases per 100,000 people but smokers have much higher rates. People who smoke 1-14 cigarettes per day have 78 cases, those smoking 15-24 have 127 cases, and heavy smokers have 251 cases. This shows that the more you smoke, the more likely you are to get lung cancer, which proves smoking causes it.

Smoking gives higher incidence than radon gas (42) and asbestos (65), so smoking seems to be worse than these other risk factors. The highest number in the table is for people smoking 25+ cigarettes per day at 251, which is the most dangerous.

However, the table doesn't show everything. Other things like genetics or pollution could also cause lung cancer but aren't in the table. Also, some people might be exposed to smoking and radon together, which could be even more dangerous. We don't know how long people were exposed to radon or asbestos, so it's hard to compare properly with smoking.

Overall, smoking does appear to be the most important risk factor based on this data because it has the highest numbers and there is a clear pattern of more smoking leading to more cancer.

Mark: 6/9

Examiner commentary: This is a solid Level 2 response that demonstrates sound understanding and makes appropriate use of data. The candidate correctly identifies the dose-response relationship and compares smoking with other risk factors using specific figures from the table. The answer recognizes some limitations, including the absence of other factors and combined exposures. However, the evaluation lacks the depth of a Level 3 response: the candidate doesn't quantify the differences as effectively (e.g., calculating fold-increases), doesn't fully explore what "most important" means in different contexts, and the discussion of limitations is less developed. The conclusion restates the position but doesn't fully acknowledge the nuances or qualify the statement as carefully as a top answer would. The response would benefit from more critical analysis of whether the data truly "proves" causation and deeper consideration of the limitations.

Grade 3 (near miss) answer

Table 3 shows that smoking causes lung cancer. Non-smokers have 8 cases but smokers who smoke 25+ cigarettes have 251 cases which is much more. This proves that smoking is the most important risk factor.

Radon gas also causes lung cancer with 42 cases and asbestos causes 65 cases. These are less than smoking so smoking is worse. The more cigarettes you smoke the more cancer you get.

However not everyone who smokes gets cancer so there must be other factors too like genetics. Some people who don't smoke still get lung cancer (8 cases) so smoking can't be the only cause.

The data shows smoking is the most important because it has the biggest numbers in the table.

Mark: 3/9

Examiner commentary: This response demonstrates Level 1 understanding with some limited progression toward Level 2. The candidate correctly identifies that smoking is associated with higher incidence and makes a basic comparison with other risk factors. However, the answer shows several weaknesses that prevent it reaching higher levels. First, the candidate conflates "causes" with "is associated with" – the data shows correlation and risk, not direct causation in individuals. Second, the evaluation is superficial: pointing out that some non-smokers get cancer is true but doesn't constitute meaningful evaluation of whether smoking is "the most important" risk factor. Third, the candidate doesn't engage meaningfully with the concept of "evaluate" – there's no real weighing of evidence or consideration of limitations beyond a brief mention of genetics. The response would improve significantly by: using data more precisely (e.g., explaining what "8 per 100,000" means), explaining the dose-response relationship more clearly, considering what the data doesn't show (combined exposures, duration, other factors), and providing a more nuanced conclusion rather than simply restating that smoking "has the biggest numbers."

Question 8(a) — Sample Answers

Grade 9 (top of Higher) answer

The human body has multiple mechanisms for defending against pathogens, working at different levels.

The first line of defense consists of physical and chemical barriers that prevent pathogens from entering the body in the first place. The skin provides an effective physical barrier as pathogens cannot penetrate the outer keratinized layer, and it also secretes antimicrobial substances in sebum that kill bacteria. The respiratory system has several defenses: the nose contains hairs and mucus that trap pathogens and dust particles, while the trachea and bronchi are lined with ciliated epithelial cells that waft mucus containing trapped pathogens upward to be swallowed. The stomach then kills these pathogens with its hydrochloric acid, which maintains a pH of around 2 that denatures bacterial enzymes and kills most microorganisms. The eyes produce tears containing lysozyme, an enzyme that breaks down bacterial cell walls.

If pathogens do enter the body, white blood cells provide the second line of defense. Phagocytes carry out phagocytosis, engulfing pathogens and digesting them with enzymes inside the cell. Lymphocytes provide a more specific response by producing antibodies – proteins that are complementary to specific antigens on the pathogen's surface. Each lymphocyte produces antibodies specific to one type of antigen. When antibodies bind to antigens, they cause pathogens to clump together, making them easier for phagocytes to engulf, or they may neutralize the pathogen directly. Lymphocytes also produce antitoxins that neutralize the harmful toxins produced by some bacteria. After an infection, some lymphocytes become memory cells that remain in the blood long-term.

Vaccination exploits this immune memory to provide protection against diseases. A vaccine contains dead or inactive pathogens, or just their antigens, which cannot cause the disease but still trigger an immune response. When the vaccine is injected, lymphocytes recognize the antigens and produce specific antibodies. Crucially, memory cells are also produced. If the person later encounters the live pathogen, these memory cells recognize it immediately and rapidly produce large quantities of antibodies. This secondary immune response is much faster and produces more antibodies than the primary response, so the pathogen is destroyed before it can cause symptoms. This means the person is immune to the disease. Vaccination programs have successfully controlled diseases like measles, polio, and tet

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