AQA GCSE Biology Biology Paper 2 (Higher), June 2025: Question 1

✅ Mark Scheme Answers (Any 2)

• The organism was buried in sediment / sand / mud / silt [1 mark]
• Soft tissues decayed or were eaten, but bones / hard parts did not decay [1 mark]
• The bones / hard parts were replaced by minerals (mineralisation) [1 mark]

💡 Key Knowledge: How Mineral Fossils Form

1. Burial: An animal dies in or near water and sinks to the sea floor, rapidly covered by sediment before scavengers destroy it.
2. Partial decay: Bacteria rot away soft tissues (skin, organs, flesh).
3. Mineralisation: Over millions of years, sediment compacts into rock while mineral-rich water seeps through, replacing bone material with minerals.

❌ Common Errors to Avoid

• Saying "buried in rock": Animals are buried in sediment, silt, or mud. It only turns into rock later!
• Vague statements like "it turned to stone": You must specify that minerals replaced the bones.
• Mentioning high pressure/compression only: Compression is ignored in the mark scheme; focus on the biological and mineral processes.

🧠 Exam Technique

Always address what happens to the soft parts vs. what happens to the hard parts. Hard parts (teeth, bones, shells) resist decay and leave impressions or get mineralised.

🧠 Alternative Method (Convert First)

You can convert to metres right at the start:

• 120 mm ÷ 1000 = 0.12 m
• 0.12 m × 17 = 2.04 m

Both methods achieve full marks!

❌ Common Calculation Traps

• Dividing by 100 instead of 1000: Remember: 10 mm = 1 cm, and 100 cm = 1 m, so 10 × 100 = 1000 mm in 1 m .
• Stopping at 2040: You will lose the final mark if you fail to give the final answer in the requested unit (metres).
• Error carried forward: If you made an arithmetic slip on 120 × 17 , you could still earn the 3rd mark if you correctly divided your incorrect number by 1000.

💡 Mnemonic to Remember the Order

Use a classic mnemonic to recall the 7 Linnaean levels in order:

Dear King Philip Came Over For Good Soup

• (Domain) → Kingdom → Phylum → Class → Order → Family → Genus → Species

❌ Distractor Words in the Box

• Community & Population are ecological levels of organisation, not classification ranks.
• Mammal is an example of a class, not the name of a taxonomic rank.
• Answers must be in the exact order: Phylum first, then Family.

✅ Acceptable Causes (Any 2, 1 mark each)

• Climate change: Global warming or an ice age [1 mark]
• Catastrophic event: Volcanic activity or asteroid collision [1 mark]
• New predators introduced or evolving [1 mark]
• New disease / pathogen spreading [1 mark]
• Loss of habitat or habitat change [1 mark]
• Competition for mates or inter-species competition other than food [1 mark]

❌ Disallowed Answers (Zero Marks)

• "Competition for food" / "Lack of food": The question specifically asked for other causes, since competition for food was already stated in the prompt.
• "Weather": Weather refers to short-term changes; extinction requires long-term climate change.
• "Pollution": Modern chemical pollution did not exist millions of years ago in the Mesozoic era.
• Unqualified "competition": Must specify competition for mates or nesting sites, as competition for food is excluded.