Excretion and Coordination: Neurones and Eye — Marking Scheme
This is the marking scheme for quiz: Excretion Quiz
Total marks: 41
Multiple-choice questions
Q1
Answer: B — Carbon dioxide. [1]
Q2
Answer: C — The medulla is the inner region. [1]
Q3
Answer: C — It carries impulses from a receptor to the CNS. [1]
Q4
Answer: A — Neurotransmitter vesicles and receptor proteins are arranged at opposite sides of the synapse. [1]
Q5
Answer: B — Fovea. [1]
Short-answer questions
Q6
Total: 5 marks
- Kidney named. [1]
- Ureter named. [1]
- Bladder named. [1]
- Urethra named. [1]
- Correct route: kidney(s) → ureter(s) → bladder → urethra → outside the body. [1]
Q7
Total: 4 marks
- Excess amino acids are deaminated in the liver; the amino group is removed. [1]
- Ammonia is produced. [1]
- The liver converts ammonia into urea. [1]
- Urea is toxic at high concentrations, so it must be excreted to prevent accumulation. [1]
Accept excess amino acids → ammonia → urea when the sequence is clear. Accept removal of the amino group as the definition of deamination.
Q8
Total: 5 marks
- High pressure in the glomerulus filters small molecules from the blood into the nephron/Bowman’s capsule, forming filtrate. [1]
- All glucose is reabsorbed into the blood. [1]
- Some ions are reabsorbed into the blood. [1]
- Most water is reabsorbed into the blood. [1]
- Urea, excess water, and excess ions remain and form urine. [1]
Q9
Total: 5 marks
- Correct pathway: receptor → sensory neurone → relay neurone → motor neurone → effector. [2]
- Relay neurone carries the impulse within the CNS. [1]
- Motor neurone carries the impulse from the CNS to the effector. [1]
- Reflex response is rapid and automatic, helping protect the body from injury. [1]
Q10
Total: 7 marks
- Cornea: refracts light entering the eye. [1]
- Iris: controls the diameter of the pupil. [1]
- Lens: refracts light to focus an image on the retina. [1]
- Retina: contains light receptors and detects light. [1]
- Optic nerve: carries impulses from the retina to the brain. [1]
- Blind spot: point where the optic nerve leaves the eye; no rods or cones are present. [1]
- Rods and cones: one valid difference, such as rods work in dim light and do not detect colour, whereas cones work in brighter light and detect colour. [1]
Q11
Total: 4 marks
(a) Bright light:
- Circular muscles contract and radial muscles relax. [1]
- The pupil constricts, reducing the amount of light entering the eye. [1]
(b) Dim light:
- Circular muscles relax and radial muscles contract. [1]
- The pupil dilates, allowing more light to enter the eye. [1]
Q12
Total: 6 marks
(a) Near object:
- Ciliary muscles contract. [1]
- Suspensory ligaments become slack. [1]
- Lens becomes thicker and more curved. [1]
(b) Distant object:
- Ciliary muscles relax. [1]
- Suspensory ligaments become tight. [1]
- Lens becomes thinner and less curved. [1]