AQA A-Level Biology Paper 1, June 2024: Question 9
6 marks · Medium difficulty · Short Answer
Calculate the number of males making mating calls in the control population and suggest and explain the effect of EE2 pollution in frog habitats on frog breeding using data from Table 6 and Table 7.
Practise this questionQuestion
Question text
09 Courtship behaviour in the frog species, Xenopus laevis, involves male frogs
calling to:
• attract sexually active females – these are advertisement calls
• start and continue mating – these are mating calls
• signal when a male is not sexually active – these are rasping calls.
Scientists investigated frog courtship behaviour by feeding a population of sexually
active male frogs a diet containing the hormone EE2. The scientists also fed a
separate control population of sexually active male frogs a diet without EE2.
They determined the percentage of males making advertisement calls or rasping calls
in each population.
Table 6 shows their results.
Table 6
Percentage of males making:
Population
Advertisement calls Rasping calls
Males fed EE2 94.0 4.0
Males not fed EE2 (control) 97.0 0.5
09.1 There were 800 males in the control population.
Each male made one type of call.
Use this information and Table 6 to calculate the number of males making mating
calls in the control population.
[1 mark]
25 Answer males
09.2 Suggest one change the scientists could make to both frog populations to increase
the number of mating calls.
[1 mark]
*0249.*3 The scientists also investigated the effect on female frog courtship behaviour of
feeding EE2 to male frogs.
Table 7 shows their results.
Table 7
Population Median time females spent in courtship / s
Males fed EE2 8
Males not fed EE2 (control) 16
EE2 is contained in human contraceptive pills. Some EE2 is released in human urine
and collects in sewage. Untreated sewage pollutes the water in frog habitats.
Suggest and explain the effect EE2 pollution in frog habitats will have on
frog breeding.
Use information from Table 6 and Table 7 in your answer.
[4 marks]
Effect on frog breeding
Explanation
Mark scheme
Show the mark scheme
Question Marking Guidance Mark Comments
20; 1
09.1 (1 x
AO2)
Add (sexually active) female(s); 1 Ignore add males
09.2 (1 x
AO3)
(Effect on breeding) Maximum 3 marks for
MP2 to MP5
1. Less mating/breeding
OR
Fewer offspring;
(Explanation)
2. Fewer advertisement calls, so females not 4 max
attracted
09.3 (4 x
OR AO2)
Fewer advertisement calls, so males not located;
3. Fewer mating calls as males less (sexually) 4. Accept mature for
active; active
4. More rasping calls as (more) males not
(sexually) active;
5. Less time spent in courtship;
How to answer it
Frog Courtship Behaviour and Environmental Pollution
This question assesses your ability to interpret complex biological data tables, perform multi-step data calculations (AO2), apply scientific knowledge to experimental design improvements (AO3), and synthesise information from multiple tables to evaluate the ecological impact of hormone pollution on animal reproduction (AO2).
Part (09.1)
Data Calculation & Interpretation
✅ Correct Answer
20
📐 Step-by-Step Calculation
- Identify total population size: 800 males in the control population.
- Find the relevant percentage: From Table 6, control males not fed EE2 had 97.0% making advertisement calls and 0.5% making rasping calls. The stem states "Each male made one type of call", meaning the remaining percentage must make mating calls.
- Calculate percentage for mating calls: 100% - (97.0% + 0.5%) = 100% - 97.5% = 2.5% .
- Calculate final number: 2.5% of 800 = (2.5 / 100) × 800 = 20 .
Part (09.2)
Experimental Design Modification
✅ Correct Answer
Add (sexually active) female(s).
🧠 Exam Technique & Guidance
This is an AO3 experimental design question. Think about what stimulates mating calls in nature. Male frogs call to interact with females. Adding females to the environment provides the biological stimulus required to trigger mating behaviour.
❌ Common Errors
Students often lose this mark by suggesting adding more males. Adding more males will increase competition or rasping calls rather than successfully triggering the specific mating calls measured in the study context.
Part (09.3)
Extended Data Synthesis & Evaluation
✅ Correct Answer
Effect on frog breeding: Less mating/breeding OR Fewer offspring.
Explanation (Any 3 from):
- Fewer advertisement calls, so females not attracted (or males not located).
- Fewer mating calls as males are less (sexually) active.
- More rasping calls as more males are not (sexually) active.
- Less time spent in courtship (referencing Table 7 data: 8 s vs 16 s).
💡 Key Knowledge & Linking Data
- Table 6 link: Males fed EE2 show a drop in advertisement calls (94.0% vs 97.0%) and an increase in rasping calls (4.0% vs 0.5%), indicating reduced sexual activity.
- Table 7 link: Females spend half the median time in courtship when paired with EE2-fed males (8 seconds compared to 16 seconds in controls).
🧠 Top-Level Exam Strategy
To secure all 4 marks, you must explicitly state the overall consequence on breeding first, and then back up your explanation by quoting or combining trends from both Table 6 and Table 7. Watch out for the examiner rule: a maximum of 3 marks can be awarded for the explanation points alone if the primary effect on breeding is omitted.
Topics
Biology · Practical skills · Data analysis · 3.7 Genetics, populations, evolution and ecosystems (A-level only)
Question and mark scheme from the AQA A-Level Biology examination, Paper 1, June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.