Mark Scheme

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

7 (a) nervous: fast, short-lived (1); hormonal: slower, longer-lasting (1). (b) pituitary (1); in the brain (1). (c) pancreas releases glucagon (1); glycogen converted to glucose (1); released into the blood (1). (8)

8 (a) ciliary muscles contract (1); suspensory ligaments slacken (1); lens becomes thicker/more curved (1). (b) image forms in front of the retina (1); corrected with a concave/diverging lens (1). (5)

9 (a) blood filtered under pressure (1); useful substances reabsorbed — all glucose, some ions and water (1); urea/excess water/ions form urine (1). (b) more ADH → more water reabsorbed (1); small volume (1); concentrated urine (1). (c) dialysis: regular, restrictive, risk of infection (2); transplant: near-normal life but donor shortage / rejection risk needing immunosuppressants (2). (10)

10 (a) transcription: gene copied into mRNA (1) which leaves the nucleus (1); translation: mRNA attaches to ribosome (1); amino acids joined in order to form the protein (1). (b) changes the base sequence (1); may change the amino acid sequence / shape of the protein (1). (c) Tt × tt → Tt, Tt, tt, tt (1 square); 2 tall : 2 short (1) = 1:1 (1). (9)

11 (a) Kingdom, Phylum, Class, Order, Family, Genus, Species (2). (b) three domains: Archaea, Bacteria, Eukaryota (1); based on DNA/RNA evidence (1); replaced earlier systems as technology improved (1). (c) choose parents with the desired characteristic (1); breed them and select offspring with the characteristic over generations (1); risk: reduced variation / inbreeding (1). (8)

12 (a) a stage/level in a food chain (1). (b) not all is eaten/digested (lost in faeces) (1); energy used in respiration/movement (1); lost as heat (1). (c) any two: restrict animal movement/keep warm; high-protein feed; fishing quotas; net size; mycoprotein (2). (6)

13 (a) warmth; moisture; oxygen (3). (b) decomposers break down dead organisms (1); respiration releases CO₂ back to the atmosphere (1). (5)

14 — Levels (6): Indicative: monitored by the thermoregulatory centre (hypothalamus). Too hot: vasodilation (more blood to skin surface → more heat lost); sweating (evaporation transfers energy). Too cold: vasoconstriction (less blood to surface → less heat lost); shivering (respiration releases heat); sweating stops; hairs raised. Negative feedback restores 37 °C.

• L3 (5–6): Both hot and cold responses, with correct mechanisms (vasodilation/vasoconstriction, sweating, shivering).
• L2 (3–4): Some correct responses for both or detailed for one.
• L1 (1–2): Simple statements.

Sample Answers with Examiner Commentary

Question 14 — Sample Answers

Grade 9 answer "Body temperature is monitored by the thermoregulatory centre in the brain (the hypothalamus), which contains receptors sensitive to blood temperature. When the body is too hot, the blood vessels supplying the skin capillaries widen (vasodilation), so more blood flows near the surface and more heat is lost to the surroundings, and the sweat glands release sweat which evaporates, transferring energy away from the skin. When the body is too cold, the skin blood vessels narrow (vasoconstriction) so less heat is lost, sweating stops, and the muscles contract rapidly (shivering), and this respiration releases heat. These responses are an example of negative feedback that keeps the core temperature around 37 °C." Mark: 6/6. Examiner commentary: Both hot and cold responses are covered with the correct mechanisms (vasodilation/vasoconstriction, sweating, shivering) and the controlling centre, framed as negative feedback. Top band.

Grade 6 answer "When you are hot you sweat and the blood vessels widen so you lose heat. When you are cold you shiver and the blood vessels get narrower so you keep heat in." Mark: 4/6. Examiner commentary: Correct responses for both hot and cold, but the technical terms vasodilation/vasoconstriction are not used and the controlling centre is not named — adding these would secure the top band.

Question 9(b) — Sample Answers

Grade 9 answer "If the blood is too concentrated, more ADH is released from the pituitary gland. This makes the kidney tubules more permeable so more water is reabsorbed back into the blood, producing a small volume of concentrated urine." Mark: 3/3. Examiner commentary: Correctly links more ADH to increased water reabsorption and to a small volume of concentrated urine.

Grade 6 answer "More ADH means more water is kept in the body so you make less urine." Mark: 2/3. Examiner commentary: Credit for more water reabsorbed and a smaller volume, but it does not say the urine is more concentrated, the third marking point.