AQA A-Level Biology Paper 1, June 2022: Question 1

10 marks · Medium difficulty · Short Answer

Describe the structure and function of the nucleus, identify cell wall polymers, explain the use of biomass over individual counts in diversity measurement, calculate an index of diversity, and suggest how farming affects species diversity.

Practise this question

Question

A series of exam questions numbered 01.1 to 01.5. Question 01.1 asks to describe the structure and function of the nucleus (4 marks). Question 01.2 asks to name main polymers in plant and fungal cell walls (1 mark). Table 1 gives plant species and total shoot biomass in g m-2 for soil with 14 fungal species. Question 01.3 asks why biomass was used instead of number of individuals (1 mark). Question 01.4 provides the index of diversity formula d = 1 - sum((n/N)^2) and asks to calculate it using Table 1 (2 marks). Question 01.5 asks how the index of diversity would differ in areas previously used to grow crops compared to nearby land, using Figure 1 and knowledge of farming effects (2 marks).
Question text

01.1 Describe the structure and function of the nucleus.

[4 marks]

01.2 Name the main polymer that forms the following cell walls.

[1 mark]

Plant cell wall

Fungal cell wall

Scientists investigated the effect of the number of fungal species in soil on the

diversity of plant species.

Table 1 shows their raw data for soil containing 14 fungal species.

Table 1

Plant species Total shoot biomass / g m–2

Poa compressa 2

Achillea millefolium 4

*03* Aster cordifolius 5

Aster novae-angliae 7

Chrysanthemum leucanthemum 15

Daucus carota 36

Fragaria virginiana 51

01.3 Suggest one reason the scientists used biomass instead of the number of individuals

of each plant species when collecting data to measure diversity.

[1 mark]

01.4 The scientists used this equation to calculate the plant species index of diversity.

𝑛𝑛 2

𝑑𝑑 = 1 − � � �

𝑁𝑁

where n = shoot biomass of each plant species

and N = total shoot biomass of all plant species

Use this equation to calculate the index of diversity for the data in Table 1.

[2 marks]

Index of diversity

Figure 1 shows the plant species index of diversity the scientists calculated when the

soil contained 0, 1, 2, 4 and 8 fungal species.

Figure 1

Figure 1 not reproduced here due to third-party copyright restrictions

01.5 Sometimes farmers stop growing crops on an area of land to allow the natural

ecosystem to recover. The plant species index of diversity of these areas previously

used to grow crops is different from nearby land that has never been used to grow

crops.

Suggest and explain how the plant species index of diversity would be different in

these areas previously used to grow crops.

Use Figure 1 and your knowledge of the effect of farming on biodiversity in your

answer.

[2 marks]

Mark scheme

Show the mark scheme Mark scheme showing accepted answers for questions 01.1 to 01.5. Question 01.1 awards up to 4 marks (max 2 for structure, max 2 for function) detailing nuclear envelope, pores, chromatin, nucleolus, and functions such as storing genetic information and transcription. Question 01.2 accepts cellulose for plants and chitin (or N-acetylglucosamine) for fungi. Question 01.3 accepts that individual organisms cannot be identified or separated, or are too numerous. Question 01.4 awards 2 marks for the correct index of diversity calculation (0.7-0.71). Question 01.5 awards 2 marks for stating that plant biodiversity is lower on previously used crop land and explaining that farming reduces biodiversity.

Question Marking Guidance Mark Comments

4 max Max 2 for structure or

function

Structure (4 x

AO1) 1. Ignore porous for

1. Nuclear envelope and pores

pores

OR

Double membrane and pores; 2 Ignore genetic

2. Chromosomes/chromatin material/information

OR 2. Accept

DNA with histones; nucleoplasm

3. Nucleolus/nucleoli;

2. Ignore promoter

01.1 Function regions OR genes OR

4. (Holds/stores) genetic information/material alleles

for polypeptides (production) Accept regulation of

OR

gene expression

(Is) code for polypeptides;

5. DNA replication (occurs); 4. Accept protein OR

6. Production of mRNA/tRNA amino acid sequences

OR OR primary structure

Transcription (occurs); for polypeptides

7. Production of rRNA/ribosomes;

6 Ignore mRNA

leaves nucleus

Cellulose (plants) and 1 For fungi, accept N-

01.2 acetylglucosamine

Chitin (fungi); (AO1)

Individual organisms could not be 1 Ignore too difficult to

identified/separated identify/distinguish

(AO2)

OR different species

Too small/numerous to count individuals Ignore too difficult to

count unless qualified

OR

Accept reference to

Too time consuming; fungi for plants

01.3

– A-LEVEL BIOLOGY – –

Correct answer for 2 marks, 0.7– 0.71;; 2 A common correct

Accept for 1 mark, (2 x answer is 0.707

AO2) Accept numbers

0.29 – 0.3 (correct calculation not subtracted from

01.4 rounding down to 0.71

1)

OR

120 (correct total shoot biomass)

1. Plant (bio)diversity is lower on (previously used) 2 Assume index of

crop land diversity refers to

(2 x

OR AO3) plants

Plant (bio)diversity is higher on land not used If no context is given

assume answer refers

(previously to grow crops);

to land previously

01.5 2. Farming reduces (bio)diversity of fungi used to grow crops

OR 1. Accept farming

reduces plant

Farming reduces fungal species richness; (bio)diversity

2. Accept farming

reduces number of

fungal species

How to answer it

Cell Structure, Biological Molecules, and Species Diversity Study Guide

What this question tests

This multi-topic exam question assesses core knowledge of eukaryotic cell ultrastructure (nucleus components and functions), biological polymers in cell walls, practical sampling limitations in ecology, mathematical processing using the Index of Diversity formula, and analytical reasoning regarding the ecological impacts of agricultural practices on biodiversity.

Part 01.1 • [4 marks]

Describe the structure and function of the nucleus.

✅ Correct Answer Framework

To score the maximum 4 marks, you must give a balanced response covering both structure and function (maximum 2 marks awarded for structure alone, or function alone).

  • Structure: Nuclear envelope (double membrane) with nuclear pores; chromosomes/chromatin (DNA associated with histones); nucleolus.
  • Function: Stores/holds genetic code for polypeptides; site of DNA replication; site of transcription (producing mRNA/tRNA); production of rRNA/ribosomes.

❌ Common Errors & Examiner Traps

  • Imbalanced answers: Listing 4 structural features and 0 functions will cap your mark at 2 out of 4. Ensure you explicitly state what the components do.
  • Vague terminology: Writing "contains information" without specifying genetic information or polypeptides.
  • Confusing organelles: Mentioning cristae or thylakoids inside the nucleus.
Mark scheme notes: Max 2 marks for structure, max 2 marks for function. "Porous for pores" is ignored; must specify nuclear envelope and pores.
Part 01.2 • [1 mark]

Name the main polymer that forms plant and fungal cell walls.

✅ Correct Answers

  • Plant cell wall: Cellulose
  • Fungal cell wall: Chitin (Accept N-acetylglucosamine )

💡 Key Knowledge

Plant cell walls are rigid structures composed of microfibrils of the polysaccharide cellulose embedded in a pectin matrix. Fungal cell walls are structurally distinct, composed of the nitrogen-containing polysaccharide chitin.

Part 01.3 • [1 mark]

Suggest why scientists used biomass instead of the number of individuals when measuring diversity.

✅ Correct Answer

Any one of the following valid practical limitations:

  • Individual plants/organisms could not be identified or separated.
  • Plants are too small or too numerous to count individually.
  • Counting individual plants would be too time-consuming.

🧠 Exam Technique

For ecological field questions asking "why use biomass/percentage cover instead of counting individuals", always think about the practical realities of plant growth (intertwined root systems, stolons, mosses, grasses forming dense swards).

Part 01.4 • [2 marks]

Calculate the index of diversity using Table 1 data.

📐 Step-by-Step Calculation

Formula: d = 1 - Σ (n / N)²

  1. Find total biomass (N): Sum all shoot biomass values from Table 1:
    2 + 4 + 5 + 7 + 15 + 36 + 51 = 120 g m⁻²
  2. Calculate (n / N) for each species:
    • 2/120 = 0.01667 → squared = 0.00028
    • 4/120 = 0.03333 → squared = 0.00111
    • 5/120 = 0.04167 → squared = 0.00174
    • 7/120 = 0.05833 → squared = 0.00340
    • 15/120 = 0.125 → squared = 0.01563
    • 36/120 = 0.3 → squared = 0.09000
    • 51/120 = 0.425 → squared = 0.18063
  3. Sum the squared fractions (Σ):
    0.00028 + 0.00111 + 0.00174 + 0.00340 + 0.01563 + 0.09000 + 0.18063 = 0.29279 (or exact fraction sum 35/120 = 0.29167 depending on rounding stages).
  4. Subtract from 1:
    1 - 0.2928 = 0.707

✅ Final Answer

0.707 (Accept range 0.70 – 0.71 )

❌ Common Calculation Traps

Students frequently calculate the sum of (n/N)² correctly (getting ~0.293) but forget to perform the final step of subtracting that value from 1 . The mark scheme awards 1 consolidation mark for reaching 0.29-0.3 if subtraction was missed.

Part 01.5 • [2 marks]

Suggest and explain how the plant species index of diversity would differ in areas previously used to grow crops.

✅ Correct Answer Points

Any two valid comparative statements required for full marks:

  • Plant biodiversity is lower on previously used crop land (or higher on land not used to grow crops).
  • Farming reduces fungal biodiversity / reduces fungal species richness.

💡 Examiner Insight & Context

Agricultural intensification (pesticides, fertilisers, monoculture planting, and ploughing) drastically reduces both flora and soil microbial/fungal diversity. When land is left to undergo secondary succession, species richness gradually recovers over time as complex webs of plant-fungal mutualisms (like mycorrhizae) re-establish.

Examiner note: Unless stated otherwise, assume the index of diversity refers to plants as per the stem data provided.

Topics

Biology · Practical skills · 3.2 Cells · 3.1 Biological molecules · 3.4 Genetic information, variation and relationships between organisms · Data analysis

Question and mark scheme from the AQA A-Level Biology examination, Paper 1, June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.