AQA GCSE Combined Science: Trilogy Biology Paper 2 (Higher), 2019: Question 4

✅ Correct answers

• Male palm cockatoos use sticks to beat on hollow branches to attract females → Behavioural
• The harmless hornet moth has black and yellow stripes to look like a bee or wasp → Structural
• Sea spiders have automatic muscle contractions that move oxygen around their bodies → Functional

💡 Key knowledge

• Structural = a physical feature of the body.
• Behavioural = something the animal does.
• Functional = an internal process or chemical action in the body.

🧠 Exam technique

• Look at what the animal is doing, not just what it looks like.
• For 2 marks, you need all three lines correct.
• If one line is wrong, you can still gain 1 mark for one or two correct matches.

❌ Common errors

• Calling the cockatoo’s stick-beating a structural adaptation because a stick is involved.
• Thinking mimicry is always behavioural — the stripes are a physical feature, so this is structural.
• Mixing up functional and behavioural: moving oxygen around the body is an internal process, not a behaviour.

✅ Correct answer points

• Growing attached to other plants gives support, so the orchid can reach more light for photosynthesis.
• Brightly coloured flowers attract pollinators / insects, increasing pollination and fertilisation.
• Large quantities of pollen increase the chance of pollen being transferred.
• Thousands of tiny, light seeds can be carried long distances to new areas, away from competitors.
• Many seeds increase the chance that some will survive and grow into new plants.

💡 Key knowledge

• Orchids rely on pollinators for sexual reproduction.
• Seed dispersal helps plants spread into new habitats.
• Competition is for light, space, water, minerals, and pollinators.

🧠 Exam technique

• The question says describe how, so you must link each adaptation to a benefit.
• To score full marks, give at least four distinct points.
• Use “therefore”, “so”, or “this means” to show the cause-and-effect link.

❌ Common errors

• Just repeating the adaptation without saying why it helps.
• Saying “bright colours make the plant pretty” instead of explaining attraction of pollinators.
• Saying tiny seeds help them “travel” without mentioning new areas or reduced competition.
• Confusing pollen with seeds.

✅ Correct answer points

• A mutation occurred in the ancestral species, creating variation in flower colour.
• Some plants had purple flowers because of this genetic variation.
• If purple flowers were better suited to the environment, those plants survived and reproduced more.
• They passed the allele / gene / DNA for purple flowers to their offspring.
• Over many generations, the purple-flowered plants became more common, until they were so different they could no longer interbreed with the ancestral species.

💡 Key knowledge

• Mutation creates new alleles.
• Natural selection means individuals with advantageous features survive and reproduce more.
• Speciation happens when populations become so different they can no longer interbreed.

🧠 Exam technique

• Write the sequence: mutation → variation → selection → inheritance → speciation.
• Marks are awarded for the process, not just for the word “evolution”.
• Use “over many generations” to show gradual change.

❌ Common errors

• Saying an individual orchid “changed because it needed to”.
• Forgetting that the new trait must be passed on to offspring.
• Describing only survival, not reproduction.
• Not mentioning that speciation takes place when populations can no longer interbreed.

✅ Correct answer

Species D

• It has the fewest amino acid differences from the ancestral sequence.
• Only one amino acid is different, so it is the most closely related.

💡 Key knowledge

• DNA determines the sequence of amino acids in a protein.
• Species with more similar amino acid sequences are usually more closely related.
• In this question, compare the sequences and count differences.

🧠 Exam technique

• Always give both parts: species and reason.
• To earn the mark for the explanation, you must make an attempt at a reason.
• Use wording like “fewest differences” or “most amino acids the same”.

❌ Common errors

• Choosing the species with the most obvious colour change instead of the most similar sequence.
• Saying “it looks most similar” without referring to the amino acid sequence.
• Forgetting to count differences carefully.

💡 Remember these definitions

• Structural = body feature
• Behavioural = action
• Functional = internal process
• Mutation = change in DNA
• Natural selection = best adapted individuals survive and reproduce more

🧠 How to score well

• Use precise biology words.
• Always explain how the adaptation helps survival or reproduction.
• For evolution questions, describe a population changing over time.
• For sequence questions, compare the number of differences.