AQA GCSE Combined Science: Trilogy Biology Paper 2 (Higher), 2020: Question 6

Recall of classification, reading a fossil timeline, drawing a time range on a graph, and doing a simple subtraction and percentage increase calculation. Full marks come from giving the exact scientific term, using the correct units, and showing clear working.

✅ Correct answer

Archaea

Accepted spelling: archaea or phonetic variants such as archea / archea may be allowed depending on examiner judgement.

💡 Key knowledge

• The three domains are Bacteria, Archaea, and Eukaryota.
• Primitive anaerobic bacteria from early Earth are linked to Archaea in this GCSE context.
• “Anaerobic” means they do not use oxygen.

🧠 Exam technique

• For a 1-mark recall question, write the single key term.
• Do not explain unless asked.
• Keep spelling clear enough for the examiner to recognise.

❌ Common errors

• Writing bacteria instead of the domain Archaea.
• Giving eukaryota, which is wrong for primitive anaerobic bacteria.
• Adding extra detail but missing the actual domain name.

✅ Correct answer

Draw a horizontal line from 415 million years ago to 65 million years ago, and label it “ammonites”.

The mark scheme allows a small range: roughly 410–420 to 65 . An oblique line can also be accepted.

💡 Key knowledge

• Ammonites first appeared at 415 million years ago.
• They disappeared in the 5th mass extinction at about 65 million years ago.
• On a timeline like this, earlier times are on the left and more recent times are on the right.

🧠 Exam technique

• Use the graph scale carefully: 415 is just left of 400.
• Make sure the line stretches across the whole living range.
• Label the line clearly with the exact word ammonites.

❌ Common errors

• Starting the line at the wrong point, such as 400 or 450.
• Stopping at the wrong extinction event.
• Forgetting the label, which can lose the mark.
• Drawing a vertical line instead of a horizontal time-range line.

📐 Calculations: step-by-step

1. Ammonites lived for: 415 − 65 = 350 million years
2. Trilobites lived for: 544 − 278 = 266 million years
3. Difference: 350 − 266 = 84 million years

Answer: 84 million years

✅ Correct answer

84 million years

The mark scheme also allows 84 000 000 or a correct answer in standard form.

🧠 Exam technique

• First find each organism’s time span.
• Then compare the two spans by subtracting one from the other.
• Always include the unit million years.
• You can still get method marks if your working is clear, even if your final number is slightly off.

❌ Common errors

• Subtracting the start dates only: 544 − 415, which is not the right method.
• Using the extinction date instead of the full lifespan.
• Forgetting that both spans must be found before comparing them.
• Missing the unit, or writing just “84”.

💡 Key knowledge

• First mass extinction = 68%
• Third mass extinction = 96%
• Percentage increase means: new value − original value, then divide by original value, then × 100.

📐 Calculations: step-by-step

1. Identify the values: 68 and 96
2. Find the increase: 96 − 68 = 28
3. Divide by the original value: 28 ÷ 68 = 0.4117647...
4. Convert to a percentage: 0.4117647... × 100 = 41.17647...%
5. Final answer: 41% or 41.2%

✅ Correct answer

41% (accept 41.2%)

Working method: [(96 − 68) ÷ 68] × 100

🧠 Exam technique

• Read the graph carefully: the values are 68 and 96.
• Use the original value in the denominator, not the new value.
• Round sensibly at the end.
• For a 3-mark calculation, show each step clearly to secure method marks.

❌ Common errors

• Using the wrong graph values.
• Doing 68 ÷ 96 instead of difference ÷ original.
• Forgetting to multiply by 100.
• Writing the answer without the % sign.
• Stopping at 41.176... without rounding appropriately.

💡 What top answers did well

• Gave the exact term Archaea for 06.1.
• Placed the ammonite line accurately between 415 and 65 million years ago and labelled it.
• Showed clear working in 06.3 by finding both lifespans before comparing them.
• Used the percentage increase formula correctly in 06.4 and rounded neatly.

❌ Where students lost marks

• Mixing up the domain level with the kingdom/group name.
• Not reading the timeline direction properly.
• Doing the wrong subtraction for time-spans.
• Not showing enough working in the percentage increase calculation.

✅ Answers to remember

• 06.1: Archaea
• 06.2: Line from 415 to 65 million years ago, labelled ammonites
• 06.3: 84 million years
• 06.4: 41%

🧠 Best exam habits

• Use the correct scientific term.
• Include units.
• Show working for calculations.
• Check that values are read from the graph accurately.