AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Knowledge of plant diseases is restricted to tobacco mosaic virus as a…
Full specification wording
Detection and identification of plant diseases: Knowledge of plant diseases is restricted to tobacco mosaic virus as a viral disease, black spot as a fungal disease and aphids as insects.
For this specification, you only need detailed knowledge of three named examples.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 4 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
For this specification, you only need detailed knowledge of three named examples. Tobacco mosaic virus is a viral disease that causes a mosaic pattern of discoloured patches on leaves, reducing photosynthesis and stunting growth. Black spot is a fungal disease, common on roses, that produces dark spots on leaves and can cause leaf loss. Aphids are insects that feed on plant sap and can weaken plants; they also act as vectors, transmitting viruses between plants. You should be able to name each example, state which group it belongs to, describe its visible effect and explain how it harms the plant. Other diseases may appear in questions as unfamiliar contexts, but the required named examples are these three.
What earns the marks
- Tobacco mosaic virus is the named viral disease and causes mosaic discolouration of leaves.
- Black spot is the named fungal disease and causes dark spots on leaves, often leading to leaf loss.
- Aphids are the named insect pest and feed on plant sap, weakening the plant.
- Aphids can act as vectors, transmitting viral pathogens from plant to plant.
- Tobacco mosaic virus reduces photosynthesis because discoloured areas of leaf contain less chlorophyll.
- Each example belongs to a different group, so the three together illustrate viral, fungal and insect causes of plant problems.
Common mistakes and how to put them right
Calling tobacco mosaic virus a fungus.
Put it right: It is a virus, and black spot is the fungal example.
Describing aphids as a disease.
Put it right: Aphids are insects that damage plants and can transmit disease.
Confusing the visible symptoms of black spot and tobacco mosaic virus.
Put it right: Black spot gives dark spots, while tobacco mosaic virus gives a mosaic pattern of discolouration.
Exam tips
- Learn the group for each named example so you can classify it quickly in a multiple-choice or short-answer question.
- Link each example to its effect on the plant, such as reduced photosynthesis or leaf loss.
- Use the term vector when explaining how aphids spread viruses.
Try the lesson
The start of the Detection and identification of plant diseases: Knowledge of plant diseases is restricted to tobacco mosaic virus as a viral disease, black spot as a fungal disease and aphids as insects. lesson, made from checked teaching notes for this specification point.
Have a go first
A gardener notices that the leaves of a tomato plant have a patchy, mottled pattern of light and dark green areas. Which named plant disease causes this type of discolouration?
Listen
For this specification, you only need detailed knowledge of three named examples. Tobacco mosaic virus is a viral disease that causes a mosaic pattern of discoloured patches on leaves, reducing photosynthesis and stunting growth. Black spot is a fungal disease, common on roses, that produces dark spots on leaves and can cause leaf loss. Aphids are insects that feed on plant sap and can weaken plants; they also act as vectors, transmitting viruses between plants. You should be able to name each example, state which group it belongs to, describe its visible effect and explain how it harms the plant. Other diseases may appear in questions as unfamiliar contexts, but the required named examples are these three. A strong answer earns marks for these points. Tobacco mosaic virus is the named viral disease and causes mosaic discolouration of leaves. Black spot is the named fungal disease and causes dark spots on leaves, often leading to leaf loss. Aphids are the named insect pest and feed on plant sap, weakening the plant. Aphids can act as vectors, transmitting viral pathogens from plant to plant. A common slip: Calling tobacco mosaic virus a fungus. Instead, it is a virus, and black spot is the fungal example. Exam tip: Learn the group for each named example so you can classify it quickly in a multiple-choice or short-answer question.
See it
Key words
Say what each word means before you turn the card.
Tobacco mosaic virus
Try answering aloud or in your head before turning the card.
Black spot
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Aphids
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Vectors
Try answering aloud or in your head before turning the card.
See every definition
- Tobacco mosaic virus
- A viral disease that causes a mosaic pattern of discoloured patches on leaves, reducing photosynthesis and stunting growth.
- Black spot
- A fungal disease, common on roses, that produces dark spots on leaves and can cause leaf loss.
- Aphids
- Insects that feed on plant sap and can weaken plants, and also act as vectors, transmitting viruses between plants.
- Vectors
- Organisms such as aphids that transmit viruses between plants.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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