AQA A-Level Biology Paper 1, June 2023: Question 3

9 marks · Medium difficulty · Short Answer

Analyze Plasmodium vivax cell structure, Golgi functions, phylogenetic evolution, calculate malaria case numbers, and explain the natural selection of malaria resistance in Africa.

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Question

Exam questions about Plasmodium vivax, including a diagram of its cellular structure (Figure 2), a phylogenetic tree showing the evolution of different strains from an African common ancestor (Figure 3), and numerical and descriptive questions about malaria cases and natural selection.
Question text

03.1 The human disease, malaria, is caused by infection with a single-celled eukaryotic

organism.

Figure 2 shows a diagram of Plasmodium vivax, one of the species that can cause

malaria.

Figure 2

Other than the Golgi apparatus, name one structure in Figure 2 which shows that

P. vivax is a eukaryote.

[1 mark]

03.2 Describe two functions of the Golgi apparatus in a eukaryotic cell.

[2 marks]

P. vivax evolved from a common ancestor in Africa. As humans migrated around the

world, new strains of P. vivax evolved.

*06* P. vivax is now extremely rare in Africa but there are several different strains of

P. vivax in other parts of the world.

Figure 3 shows a phylogenetic diagram of the evolution of these different strains.

Figure 3

03.3 What does Figure 3 suggest is the order of human migration out of Africa?

Tick ( ) one box.

[1 mark]

Europe, India, East Asia, Central America, South America

India, East Asia, Europe, South America, Central America

India, Europe, East Asia, Central America, South America

South America, Central America, East Asia, Europe, India8

03.4 There are an estimated 229 million cases of human malaria worldwide per year.

94% of these cases are found in Africa, but are not caused by P. vivax.

P. vivax does cause 61% of the cases of human malaria outside Africa.

Use this information to calculate the number of cases worldwide caused by

P. vivax each year.

[1 mark]

Answer cases of malaria

03.5 In Africa today, most of the human population are resistant to malaria caused by

P. vivax.

Use your knowledge of natural selection to explain why this resistance is so common

in Africa.

[4 marks]

Mark scheme

Show the mark scheme Mark scheme providing acceptable answers for identifying eukaryotic structures, Golgi apparatus functions, interpreting the phylogenetic tree, calculating malaria cases, and outlining the process of natural selection for malaria resistance.

Question Marking Guidance Mark Comments

Membrane-bound organelle(s) Ignore rER OR rough

ER

OR

Accept ‘80S

ribosomes’ OR

Mitochondrion/mitochondria

‘large(r) ribosomes’

OR Reject smooth

1 Reject nucleolus

Vesicle(s)/lysosomes

03.1 Reject cell membrane

(AO1)

OR

(Rough) endoplasmic reticulum

OR

Nucleus/(double) nuclear membrane/pore(s)/

nuclear envelope;

1. Modify/package/transport proteins Accept processes for

modify

OR

1. and 2. Accept ‘adds

carbohydrate to’ for

Make/transport glycoproteins;

modify

2. Modify/package/transport lipids

1. Accept ‘adds lipid

to’ for modify

OR

1. Accept lipoprotein

Make/transport glycolipids; 2 max for glycoprotein

03.2 3. Forms/releases vesicles/lysosomes; (2 x 1 or 2. Accept

AO1) chylomicron for

glycoprotein/glycolipid

2. Accept

phospholipid for lipid

Accept additional

marking point,

4. Make/transport

polysaccharides, but

ignore cellulose

Answer key:

03.3 India, Europe, East Asia, Central America, South

(AO3)

America

Correct answer of 8.3814 million/8 381 400/8.3814

x 106 Accept any correct

03.4 numerical equivalent

OR (AO2)

answer

8.4 million/8400000/8.4 x 106;

Reject gene for allele

1. Mutation produced allele;

only once

2. Those with allele/resistance less likely to/do not

1. Reject ‘mutation

get malaria/P vivax

caused by

OR infection/exposure

to P. vivax’.

Those with allele/resistance survive malaria/P

vivax; 2. Accept converse;

4 eg ‘people lacking

3. (So more likely to) reproduce and pass on the

(2 x the allele die from

03.5 allele;

AO1, 2 malaria’

4. (Over generations) allele frequency x AO2)

increases; 4. Accept description

of increasing

frequency of allele

eg ‘higher

proportion’, ‘more

common’ but ‘ignore

increase in number

of allele’

How to answer it

Cells, Evolution and Natural Selection in Plasmodium vivax

What this question tests

This question assesses core competencies across multiple topics: identifying eukaryotic cellular structures from diagrams, understanding organelle functions, interpreting phylogenetic branching diagrams, executing multi-step data calculations, and applying the principles of natural selection and allele frequency change to human populations.

Part (03.1): Identifying Eukaryotic Features

Other than the Golgi apparatus, name one structure in Figure 2 which shows that P. vivax is a eukaryote. [1 mark]

✅ Correct Answer

Any one of the following:

  • Membrane-bound organelle(s)
  • Mitochondrion / mitochondria
  • Vesicle(s) / lysosomes
  • (Rough) endoplasmic reticulum
  • Nucleus / (double) nuclear membrane / pore(s) / nuclear envelope
  • 8S ribosomes / large ribosomes

❌ Common Errors

Students frequently lose this mark by naming prokaryotic or general sub-cellular structures that do not uniquely prove eukaryote status in this context, or by confusing cell components.

  • Rejecting rough ER if written as rER or rough ER (though full name is safest).
  • Rejecting smooth endoplasmic reticulum.
  • Rejecting nucleolus or cell membrane.
Mark breakdown: 1 mark for AO1 (Recall of eukaryotic ultrastructure).

Part (03.2): Functions of the Golgi Apparatus

Describe two functions of the Golgi apparatus in a eukaryotic cell. [2 marks]

✅ Correct Answer

Any two of the following distinct points (2 max):

  • Modify, package, or transport proteins / lipids.
  • Make and transport glycoproteins or glycolipids (accept adding carbohydrates to proteins/lipids).
  • Form and release vesicles or lysosomes.

💡 Key Knowledge

The Golgi apparatus acts as the processing and sorting hub of the cell. It receives proteins from the rough ER, alters them chemically (e.g., adding sugar chains to form glycoproteins), packages them into secretory vesicles, and dispatches them to their target destinations.

Mark breakdown: 2 marks total (2 × AO1). Points must be distinct functional statements.

Part (03.3): Interpreting Phylogenetic Trees

What does Figure 3 suggest is the order of human migration out of Africa? Tick (v) one box. [1 mark]

✅ Correct Answer

The correct box to tick is:

India, Europe, East Asia, Central America, South America

🧠 Exam Technique

Trace the phylogenetic tree from left to right (along the time axis) starting from the "African Common Ancestor". Look at the branching points (nodes) that split off first. The branches splitting off earliest represent populations that separated and migrated earliest.

Mark breakdown: 1 mark for AO3 (Interpreting scientific data and evolutionary trees).

Part (03.4): Epidemiological Calculation

Use this information to calculate the number of cases worldwide caused by P. vivax each year. [1 mark]

📐 Calculation Steps

  1. Identify total cases: 229 million worldwide per year ( 229,000,000 ).
  2. Determine percentage outside Africa: 100% - 94% = 6% of cases occur outside Africa.
  3. Calculate proportion caused by P. vivax: 61% of those cases outside Africa are caused by P. vivax.
  4. Execute calculation:
    Total global cases × (Fraction outside Africa) × (Fraction caused by P. vivax)
    = 229,000,000 × 0.06 × 0.61
    = 229,000,000 × 0.0366
    = 8,381,400 (or 8.38 million)

✅ Accepted Numerical Answers

Examiners accept any numerical equivalent:

  • 8.3814 million
  • 8 381 400
  • 8.3814 × 10⁶
  • 8.4 million / 8,400,000 / 8.4 × 10⁶ (if rounded)
Mark breakdown: 1 mark for AO2 (Applying quantitative skills to biological data).

Part (03.5): Natural Selection and Allele Frequency

Use your knowledge of natural selection to explain why this resistance is so common in Africa. [4 marks]

✅ Correct Answer (Mark Scheme Points)

  1. Mutation: Random mutation produced the resistance allele.
  2. Differential survival: Individuals with the allele/resistance are less likely to get malaria / are more likely to survive infection by P. vivax.
  3. Reproduction: Survivors are more likely to reproduce and pass on the advantageous allele to their offspring.
  4. Frequency shift: Over generations, the frequency of the resistance allele increases in the African gene pool.

❌ Common Errors & Pitfalls

  • Lamarckian phrasing: Never state that P. vivax exposure "caused" or "induced" the mutation. Mutations are spontaneous and random; selection simply filters them.
  • Incorrect terminology: Do not use "gene" when referring to alleles. You must state "allele frequency increases", not "number of alleles increases".
  • Vague survival: Simply stating "they don't die" is insufficient; you must explicitly link survival to reproductive success and allele transmission.
Mark breakdown: 4 marks total (2 × AO1, 2 × AO2). Standard 4-marker narrative structure for natural selection mechanisms.

Topics

Biology · 3.2 Cells · 3.4 Genetic information, variation and relationships between organisms · 3.7 Genetics, populations, evolution and ecosystems (A-level only)

Question and mark scheme from the AQA A-Level Biology examination, Paper 1, June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.