Mark Scheme

Section A: 1. B; 2. B; 3. C; 4. B; 5. B; 6. B. (6)

7 (a) equal-sized cylinders (1); blotted and massed before/after (1); controlled time/temperature/volume (1). (b) water concentration higher outside than inside (1); water enters by osmosis (1); across the partially permeable membrane (1). (c) allows for different starting masses (1); so a fair comparison (1). (8)

8 (a) any two: skin barrier; mucus and cilia in airways; stomach acid (2). (b) phagocytosis (1); produce antibodies (1); produce antitoxins (1). (c) overuse selects for resistant bacteria (1); resistant ones survive and reproduce (1); passing on resistance (1). (8)

9 (a) pancreas (1). (b) pancreas releases insulin (1); cells take up glucose (1); excess stored as glycogen (1). (c) Type 1: no insulin produced, treated with injections (2); Type 2: cells stop responding to insulin, linked to obesity, treated with diet/exercise (2). (8)

10 (a) dominant: shown with one copy (1); recessive: needs two copies (1). (b) Ff × Ff → FF, Ff, Ff, ff (1); ff has cystic fibrosis (1); probability 1 in 4 / 25% (1). (c) sex chromosomes XX female, XY male (1); 50% chance from the sperm carrying X or Y (1). (8)

11 (a) vary distance of a lamp (1); measure bubbles of O₂ per minute / gas volume (1); use 1/distance² for light intensity (1). (b) another factor (CO₂ or temperature) becomes limiting (1); so increasing light no longer increases the rate (1). (5)

12 (a) place quadrats randomly (1); count plants / find mean per quadrat (1); scale up by total area (1). (b) abiotic example with effect (e.g. less light → fewer plants) (2); biotic example with effect (e.g. new predator → prey fall) (2). (7)

13 (a) algae and plants evolved (1); photosynthesis produced oxygen (1). (b) any two: ice melting/sea level rise; extreme weather; changing species distribution; reduced food production (2). (4)

14 — Levels (6): Indicative: vaccine contains dead/inactive pathogen or antigens; white blood cells produce antibodies; memory cells remain; on re-infection, faster and larger response destroys the pathogen before illness. Herd immunity: if most people are immune, the pathogen cannot spread easily, protecting the unvaccinated.

• L3 (5–6): Explains the memory-cell mechanism and herd immunity clearly.
• L2 (3–4): Some of the mechanism or herd immunity.
• L1 (1–2): Simple statements.

Sample Answers with Examiner Commentary

Question 14 — Sample Answers

Grade 9 answer "A vaccine contains a dead or inactivated form of the pathogen, or its antigens. When injected, the white blood cells recognise the antigens and produce specific antibodies, and importantly they also produce memory cells that stay in the blood. If the real pathogen later enters the body, these memory cells allow antibodies to be produced much faster and in greater numbers, destroying the pathogen before the person becomes ill — this gives long-term protection. If a large proportion of the population is vaccinated, the pathogen cannot spread easily from person to person, so even people who are not vaccinated are protected. This is called herd immunity." Mark: 6/6. Examiner commentary: Both required ideas — the memory-cell basis of long-term immunity and herd immunity — are explained accurately. Top band.

Grade 6 answer "A vaccine has a weak version of the pathogen so your white blood cells make antibodies. Next time you can fight it off quickly. If lots of people are vaccinated the disease can't spread as easily." Mark: 4/6. Examiner commentary: Correct on antibody production, the faster secondary response and herd immunity, but it does not mention memory cells, the key to long-term protection. That omission caps it below the top band.

Question 9(c) — Sample Answers

Grade 9 answer "In Type 1 diabetes the pancreas produces little or no insulin, so it is treated with insulin injections. In Type 2 diabetes the body cells stop responding to insulin; it is strongly linked to obesity and is usually treated with a controlled diet and regular exercise." Mark: 4/4. Examiner commentary: Cause and treatment correct for both types, with the obesity risk factor for Type 2. Full marks.

Grade 6 answer "Type 1 is when you don't make insulin and need injections. Type 2 is when your body doesn't use insulin properly and you control it with diet." Mark: 3/4. Examiner commentary: Correct causes and treatments, but the link between Type 2 and obesity is missing, which is a commonly credited marking point.