Fungal and Protist Diseases

Rose black spot and malaria — two diseases where prevention beats treatment. The mark-scheme insists on "vector" and named control measures.

SPEC 8461 • MODULE 3 • LESSON 3.03

The Word the Mark Scheme Demands

For malaria transmission, AQA mark schemes reward one specific word above all others.

The mark scheme credits the spec term "mosquito" or "vector". Generic terms like "insect" are too vague and may not score the mark. — Recurring AQA Mark-Scheme Pattern

Why This Lesson

The spec names one fungal disease (rose black spot) and one protist disease (malaria). Both are highly visual, both spread in unusual ways, and both have spec-specific prevention measures that examiners want named precisely.

Learning Objectives

By the end of this lesson, you'll be able to:

Objective 1

Describe rose black spot — symptoms, spread, and treatment — using spec language ("purple or black spots", "yellow", "drop early", "fungicides").

Objective 2

Describe malaria — including the role of the mosquito vector in the protist's life cycle, recurrent fever symptoms, and named prevention measures.

Objective 3

Use mark-scheme language — "vector" or "mosquito" (never "insect"); "preventing the vectors from breeding"; "mosquito nets to avoid being bitten".

Spec ref: 4.3.1.4, 4.3.1.5 · Paper: 1 · Tier: Higher

Rose Black Spot — Symptoms

Rose black spot is the spec's only named fungal disease. It's a plant disease affecting roses.

Discrete purple / black spots — distinct from TMV's mosaic pattern

Spec Symptoms

Purple or black spots develop on leaves.

Leaves often turn yellow and drop early.

Effect on Plant

Affects the growth of the plant as photosynthesis is reduced — same mechanism as TMV in plant disease questions.

Rose Black Spot — Spread & Treatment

Spread (Spec Language)

Spread in the environment by water or wind.

(Spores are released into the environment — once they land on healthy plants, infection can spread rapidly through a rose garden.)

Treatment

Two spec-named methods:

→ Fungicides (chemicals that kill the fungal pathogen)

→ Removing and destroying affected leaves (physical control)

Use one or both — the spec says "and/or".

Exam Tip

For "how would you reduce the spread of rose black spot" questions, name both treatments. The mark scheme typically credits each separately. "Use fungicides" alone gets one mark; pairing with "remove and destroy affected leaves" gets two.

Don't Confuse

Rose black spot is spread by water or wind (the spec's exact wording for fungi). Don't confuse with malaria's vector route or TMV's plant-to-plant contact.

Malaria — The Protist Pathogen

Malaria is the spec's only named protist disease. The pathogen is the malarial protist — a single-celled eukaryote that needs a vector to spread.

Vector

A vector is an organism that carries the pathogen from one host to another. For malaria, the vector is the mosquito.

Spec Statement

"The pathogens that cause malaria are protists. The malarial protist has a life cycle that includes the mosquito."

Mark-Scheme Vocabulary

For the carrier organism, use the spec term "mosquito" or "vector". Generic phrases like "insect" are too vague and may not earn the mark — specificity wins.

Malaria — Life Cycle & Transmission

The "life cycle that includes the mosquito" works as a transmission cycle between hosts. Every stage matters for the mark scheme.

"Life cycle that includes the mosquito" — vector transmission between human hosts

Malaria — Prevention

The spec gives two named control measures. Both target the vector — the spec's named prevention approach is vector control, breaking the transmission cycle.

Control 1 — Breeding

Preventing the vectors, mosquitos, from breeding (spec language).

Mosquitoes lay eggs in stagnant water. Draining puddles, ponds, and water containers reduces breeding sites.

Control 2 — Bites

Using mosquito nets to avoid being bitten (spec language).

Physical barrier prevents the mosquito reaching skin. Most effective at night when mosquitoes feed.

Exam Tip

Both methods break the transmission cycle. Use the spec phrases word-for-word: "preventing the vectors from breeding" and "mosquito nets to avoid being bitten". Pair with why they work (e.g., "no breeding → fewer mosquitoes → less transmission") for full credit on explain questions.

Fungal vs Protist — At a Glance

FeatureRose Black Spot (Fungal)Malaria (Protist)

HostPlants (roses)Humans

Visible signsPurple / black spots on leaves; leaves yellow and drop earlyRecurrent episodes of fever; can be fatal

EffectAffects growth as photosynthesis is reducedDamages cells; fever cycles disable the host

SpreadBy water or wind (spores)By vector (mosquito) — life cycle includes the mosquito

ControlFungicides; remove and destroy affected leavesPrevent mosquitos breeding; use mosquito nets

Pattern Recognition

Neither has a vaccine; neither is treated with antibiotics (antibiotics target bacteria, not fungi or protists). Control is about physical / chemical / environmental measures — not the body's immune system.

Mark-Scheme Language

The right words win marks. Vague or generic terms lose them.

✗ Generic (loses marks)✓ Mark-scheme term

"insect carries malaria"" mosquito (vector) carries the protist"

"stops mosquitoes biting"" mosquito nets to avoid being bitten "

"kills mosquitoes"" preventing the vectors from breeding "

"the leaves go dark"" purple or black spots on leaves"

"spray the plant""treat with fungicides " + " remove and destroy affected leaves "

"black spot kills plants""affects growth as photosynthesis is reduced "

Worked Example — Steps 1 & 2

"Describe how the malarial protist is transmitted from one person to another." — Exam-style question · [3 marks]

Step 1 — Read the question

Command word: "Describe" — sequential, no reasoning needed. Mark allocation: 3 marks = three distinct points. Topic: malaria transmission.

Step 2 — Identify the pattern

3-mark mechanism question. Each mark = one named step in the transmission chain. Mark scheme likely accepts:

→ Mosquito (vector) bites infected human — takes up protist (1 mark)

→ Mosquito then bites an uninfected human — transmits protist (1 mark)

→ Protist enters the bloodstream of the new host (1 mark)

Mark Allocation Tip

Three marks = three named steps. Don't write one long sentence with the word "mosquito" once — write three points, each with the action verb (bites · transmits · enters). The mark scheme rewards named steps.

Worked Example — Steps 3, 4 & 5

Step 3 — Plan

Three marks → three named steps in the transmission chain. Step A: mosquito bites infected human and takes up protist. Step B: mosquito bites uninfected human. Step C: protist enters the new host's bloodstream.

✗ 0–1 marks

"Insects carry malaria from one person to another. They spread it by biting."

"Insects" is too generic (use "mosquito"); only one vague step described.

✓ 3 marks

"A mosquito (vector) bites an infected person and takes up the protist. The same mosquito then bites an uninfected person. The protist enters the new person's bloodstream, infecting them."

Three named steps. "Mosquito" / "vector" used. Action verbs present.

Step 5 — Match to mark scheme

Mark scheme accepts: (1) "mosquito bites infected person" + "takes up protist", (2) "(same) mosquito bites uninfected person", (3) "protist enters new host / bloodstream". ✓ 3 marks awarded.

Three Examiner Alerts

Alert 1 — "Mosquito" not "Insect"

For malaria's vector, write "mosquito" or "vector" — the spec terms. "Insect" is too generic and may not score. Pair "mosquito" with "vector" where possible for safety.

Alert 2 — Name BOTH prevention methods

For "how is malaria controlled" questions, give both spec measures: "preventing the vectors from breeding" AND "mosquito nets to avoid being bitten". Each is one mark — listing both maximises score.

Alert 3 — Black spot affects PHOTOSYNTHESIS

For "explain how rose black spot affects the plant", the mark scheme wants "photosynthesis is reduced" — not just "the plant gets sick" or "it dies". Same mechanism as TMV in plant disease answers.

Common Errors — Wrong vs Right

High-frequency errors on fungal and protist disease questions.

✗ Wrong (loses marks)✓ Right (mark-scheme version)

"insect spreads malaria"" mosquito (vector) spreads malaria"

"malaria is treated with antibiotics""malaria is a protist disease — antibiotics target bacteria, not protists; control is by vector management "

"rose black spot is bacterial""rose black spot is fungal — spread by water or wind "

"black spot kills the leaves"" purple / black spots develop; leaves turn yellow and drop early "

"malaria gives you a fever""causes recurrent episodes of fever — can be fatal"

Recap — Three Takeaways

1

Rose black spot (fungal). Plant disease · purple / black spots · leaves yellow + drop early · reduces photosynthesis · spread by water or wind · treated with fungicides + remove leaves.

2

Malaria (protist). Caused by malarial protist · life cycle includes the mosquito vector · recurrent fever · can be fatal · control by preventing breeding + mosquito nets.

3

Mark-scheme words. Use "mosquito" or "vector" (never "insect"). Pair prevention measures with why they work for explain questions. Name "photosynthesis" for rose black spot's plant effect.

Exam Tip

Three things. You're set for any fungal or protist disease question on Paper 1. The spec only names one example of each — so spec-specific language is essential.

Summary

Key Points

One named fungal disease — rose black spot (plant) — the only fungal disease in the spec

One named protist disease — malaria (human, via mosquito vector) — the only protist disease in the spec

Fungal spread: water or wind

Protist spread: vector (mosquito) — life cycle includes the mosquito

Both prevented by environmental / physical / chemical control , not by antibiotics (antibiotics target bacteria)

Rose black spot reduces photosynthesis ; malaria causes recurrent fever

Rose Black Spot Quick Recall

Symptoms: purple / black spots · yellow leaves · drop early

Effect: photosynthesis reduced

Spread: water or wind

Treatment: fungicides + remove affected leaves

Malaria Quick Recall

Pathogen: malarial protist

Vector: mosquito (life cycle includes it)

Symptoms: recurrent fever · can be fatal

Control: prevent breeding + mosquito nets

Exam Tip

The biggest mark loss on this topic is generic vocabulary — "insect", "germs", "the plant gets sick". Name the pathogen type, name the vector, name the photosynthesis effect. Next: Lesson 3.04 — Human Defence Systems.