AQA AS Level Biology Paper 2, June 2023: Question 9

8 marks · Medium difficulty · Practical Techniques & Data Analysis

Analyze fish gill measurements, calculate surface area, relate surface area to fish activity level, and complete a phylogenetic classification table.

Practise this question

Question

Question text

09 Scientists dissected gills from several species of fish. They recorded:

• the mass of the whole fish

• the total number of gill filaments

• the mean length of one filament

• the mean number of lamellae per mm

• the mean surface area of one lamella.

09.1 It was not possible for the scientists to measure the length of every filament and the

surface area of every lamella.

Suggest how they collected data to give a reliable mean for these variables.

[2 marks]

09.2 From these measurements, the scientists calculated the total surface area of the gas

exchange surface on the gills of each fish species.

Calculate the total surface area of the gills of a fish with the following measurements:

• total number of gill filaments = 595

• mean length of one filament = 2.86 mm

• mean number of lamellae per mm = 16

• mean surface area of one lamella = 0.66 mm2

Give your answer in mm2 to an appropriate number of significant figures.

and

Show your working.

[2 marks]

24 mm2

09.3 Table 5 shows the scientists’ data for two species of fish.

Table 5

Mean total surface area

Fish species Mean fish mass / g 2

*23* of the gills / mm

Opsanus tau 305 46 100

Trachurus trachurus 250 252 500

One of these fish spends most of its time not moving, waiting to catch passing prey.

The other species is very active, hunting mobile prey.

Suggest which of the species in Table 5 is the very active fish species.

Explain your answer.

[2 marks]

Very active fish species

Explanation

09.4 Complete Table 6 to show the phylogenetic classification for these two species.

[2 marks]

Table 6

Taxon Opsanus tau Trachurus trachurus

Animalia

Chordata

Class Actinopterygii Actinopterygii

Batrachoidiformes Carangiformes

Family Batrachoididae Carangidae

Genus

Species tau trachurus

Mark scheme

Show the mark scheme

Question Marking Guidance Mark Comments

1. Allow in context

1. Random samples;

of fish or gills

2. Large sample size; 2. If a specified

2 number is given,

it must be 10 or

09.1 (2 x

more.

AO3) 2. Accept ‘many’/

‘multiple’ for large

sample but ignore

‘several’

Correct answer of 18 000/1.8 × 104 = 2 marks;;

1 mark for

Correct answers not given to 2sf (17 969.952) Accept

17970/17969.9

09.2 OR

(2 x

Evidence of 1701.7 (total length of filaments) AO2)

27 227.2 – 27370 (total number of lamellae)

Incorrect fish name

(Trachurus trachurus) – no mark

= zero

1. More oxygen uptake/diffusion Accept just

OR 2 ‘Trachurus’ or

‘trachurus’

09.3 More gas exchange; (2 x

AO2) ‘More’ required once

2. More energy/ATP from respiration;

only

1 mark for first column

1 mark for 2nd and 3rd column all correct

Kingdom Animalia Animalia

Phylum/Phyla Chordata Chordata

Class Actinopterygii Actinopterygii

09.4 (2 x

Order Batrachoidiformes Carangiformes AO2)

Family Batrachoididae Carangidae 15

Genus Opsanus Trachurus

Species tau trachurus

How to answer it

Fish Gills, Gas Exchange & Biological Classification

What this question tests

This question assesses your understanding of gas exchange surfaces in aquatic organisms (specifically fish gills), your ability to plan reliable sampling methods, multi-step calculation competencies involving surface area scaling, interpreting physiological adaptations based on quantitative data, and recalling hierarchical taxonomic ranks.

Question 09.1

Sampling Reliability for Gill Dimensions

✅ Correct Answer

Random samples / Random selection of filaments or lamellae
Large sample size (accept 'many', 'multiple', or specific numbers if ≥ 10)

💡 Key Knowledge

Biological variation across a single organism means measuring every structure is impossible. Random sampling prevents sampling bias, ensuring the selected filaments/lamellae are representative of the whole organism.

🧠 Exam Technique

Examiners look for precise methodological keywords. Vague terms like "take a lot" need care, but AQA accepts "many" or "multiple". Always pair random sampling with sample size requirements.

Marks: 2 marks (2 × AO3 - Practical Skills)

Question 09.2

Calculating Total Gill Surface Area

📐 Step-by-Step Calculation

Find total lamellae across all filaments:
595 filaments × (mean number of lamellae per mm × mean length) OR multiply total filaments by mean length to get total length, then multiply by lamellae per mm.
Total length = 595 × 2.86 = 1701.7 mm
Total number of lamellae = 1701.7 × 16 = 27,227.2
Calculate total surface area (accounting for both sides of a lamella? Use given single area directly):
27,227.2 lamellae × 0.66 mm² = 17,969.952 mm²
Apply significant figures:
Data is given to 2 and 3 sig figs. The lowest precision is 2 sf (e.g., 16). Therefore, round 17,969.952 to 2 significant figures: 18 000 (or 1.8 × 10⁴ ).

✅ Final Answer

18 000 mm² (or 1.8 × 10⁴ mm²)

(Accept 17 970 or 17 969.9 if 2sf instruction was missed, but 2sf gives the full 2 marks).

❌ Common Errors

Failing to round to the appropriate number of significant figures (leaving it as 17969.952).
Arithmetic errors when compounding filament counts and lamellae per mm densities.

Marks: 2 marks (2 × AO2 - Problem Solving / Calculation)

Question 09.3

Relating Gill Surface Area to Lifestyle

✅ Correct Answer

Very active fish species: Trachurus trachurus

Explanation: Has a much larger total surface area of gills (252 500 mm² vs 46 100 mm²), allowing for more oxygen uptake / greater rate of diffusion to support higher rates of respiration / ATP production for muscle contraction.

🧠 Exam Technique & Marking Points

Mark 1: Correctly identify Trachurus trachurus and state it has greater oxygen uptake/diffusion or more gas exchange.
Mark 2: Link this directly to more energy/ATP produced via respiration. Note: The word 'more' is required only once in the mark scheme, but comparisons must be explicit.

Marks: 2 marks (2 × AO2 - Analysis of Data)

Question 09.4

Phylogenetic Classification Hierarchy

💡 Key Knowledge: Taxonomic Ranks

Remember the taxonomic hierarchy: Kingdom, Phylum, Class, Order, Family, Genus, Species (mnemonic: King Prawn Curry Or Fat Greasy Sausages).

✅ Completed Table (Table 6)

Taxon	Opsanus tau	Trachurus trachurus
Kingdom	Animalia	Animalia
Phylum	Chordata	Chordata
Class	Actinopterygii	Actinopterygii
Order	Batrachoidiformes	Carangiformes
Family	Batrachoididae	Carangidae
Genus	Opsanus	Trachurus
Species	tau	trachurus

Marks: 2 marks (1 mark for the first missing taxon column / Kingdom 'Animalia', 1 mark for completing the remaining blank taxonomic boxes correctly).

Topics

Biology · Practical skills · 3.3 Organisms exchange substances with their environment · 3.4 Genetic information, variation and relationships between organisms · Data analysis · Experimental design

Question and mark scheme from the AQA AS Level Biology examination, Paper 2, June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.