AQA GCSE Combined Science: Trilogy Biology Paper 2 (Higher), 2018: Question 4

Key skills

• Recall biology terms
• Use correct scientific vocabulary
• Do a one-step calculation
• Describe a trend clearly

How marks are awarded

• Usually 1 mark per correct idea
• Calculations can earn method marks
• Units matter: s and ms
• Descriptions must match the data

Big mistakes to avoid

• Mixing up synapse and relay neurone
• Saying impulses are chemical all the way along a neurone
• Forgetting the brain is involved in conscious actions
• Giving “directly proportional” for the table

✅ Correct answers

P: synapse

Q: relay neurone

💡 Key knowledge

• A synapse is the tiny gap between neurones.
• A relay neurone carries impulses within the central nervous system.
• In a reflex arc, impulses pass from sensory neurone to relay neurone to motor neurone.

🧠 Exam technique

• Use the diagram position to help you.
• If the label points to a gap between neurones, think synapse.
• If the label points to the neurone in the spinal cord, think relay neurone.

❌ Common errors

• Calling P a neurone instead of the gap between neurones.
• Writing interneuron is acceptable, but make sure the spelling is close enough.
• Mixing up sensory and motor neurones.

✅ Correct answers

Along a neurone: information travels as an electrical impulse.

Across gap P: information travels by diffusion of chemicals / neurotransmitters.

💡 Key knowledge

• Inside neurones, impulses are electrical.
• Across a synapse, the signal becomes chemical.
• Neurotransmitters diffuse across the synapse and trigger the next neurone.

🧠 Exam technique

• For full marks, make a direct comparison: electrical vs chemical.
• You can also say “electrical impulse” and “chemical messenger”.
• If you mention both electrical and chemical in the correct order, that can still gain credit.

❌ Common errors

• Saying the impulse stays electrical across the synapse.
• Saying “signal” without explaining the type of signal.
• Writing “movement of neurotransmitter” is fine, but only if it clearly means chemical transmission.

✅ Correct answer

The impulse has to travel to the brain (and back), so it takes longer.

💡 Key knowledge

• Reflex actions go through the spinal cord only.
• Conscious actions involve the brain processing the information.
• More distance and more processing time means a slower response.

🧠 Exam technique

• One clear reason is enough for the mark.
• You can also say the pathway is longer or there are more synapses.
• Always link your answer to the brain or processing time.

❌ Common errors

• Saying “because it is deliberate” without explaining why that makes it slower.
• Talking about muscles instead of the nervous pathway.
• Forgetting to mention the brain at all.

📐 Calculations: step by step

1. Use the speed equation: speed = distance ÷ time
2. Rearrange: time = distance ÷ speed
3. Substitute the values: time = 1.6 ÷ 120
4. Calculate: time = 0.0133... s
5. Convert to milliseconds: 0.0133... s × 1000 = 13.3... ms

Final answer: 13.3 ms (or 13 ms if rounded sensibly)

✅ Correct answer

Time = 13.3 ms

Accept 13.33... ms or 13 ms depending on rounding.

💡 Key knowledge

• speed = distance ÷ time
• 1 second = 1000 milliseconds
• Always check the units asked for in the question

🧠 Exam technique

• Show the equation first to secure method marks.
• Use units carefully: metres, seconds, milliseconds.
• Marks are available for the correct rearrangement and the correct conversion.

❌ Common calculation traps

• Doing 120 ÷ 1.6 instead of 1.6 ÷ 120
• Forgetting to convert seconds to milliseconds
• Writing 0.0133 ms instead of 0.0133 s
• Mixing up the equation and not rearranging it properly

✅ Correct answer

As age increases, the time for the muscle to contract increases, and it increases at an increasing rate.

💡 Key knowledge

• 30 years: 18.9 ms
• 80 years: 37.0 ms
• The increase is not the same each time, so it is not directly proportional.

🧠 Exam technique

• Describe the overall trend first: increases with age.
• Then add the pattern in the size of increase: at an increasing rate.
• Use data to support the trend if you can.

❌ Common errors

• Saying it is directly proportional — do not accept this.
• Only saying “it goes up” without mentioning the rate of increase.
• Quoting one value without describing the relationship.

Remember these terms

• Synapse
• Relay neurone
• Electrical impulse
• Neurotransmitter

Best exam habits

• Use precise biology vocabulary
• Show working in calculations
• Check units and final form of answer
• Describe trends clearly using comparative language

Last-minute warning

• Don’t confuse the synapse with a neurone
• Don’t write chemical transmission along the whole neurone
• Don’t forget milliseconds in the calculation
• Don’t say “directly proportional” for the age table