OxfordAQA International A Level Biology
OxfordAQA International A Level Biology 3.2.9 The Role of Aphids in Spreading Plant Viruses Exam Questions
Free OxfordAQA International A Level Biology revision for 3.2.9 The Role of Aphids in Spreading Plant Viruses: what you need to know, common mistakes and exam-style questions with answers. Covers plant virus diseases, their symptoms and effects on crops, and aphids as phloem-feeding vectors.
Practise 3.2.9 The Role of Aphids in Spreading Plant Viruses with past papers
Once you have learnt this topic, find the 3.2.9 The Role of Aphids in Spreading Plant Viruses questions in real OxfordAQA International A Level Biology past papers and mark them with the mark scheme. Doing lots of real questions is the quickest way to learn how examiners ask about each idea.
StemUp mark scheme flashcards
A-Level Biology Flashcards for 2027 Onwards
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Then test yourself with the questions on this page.
From £10.99View flashcards
About OxfordAQA International A Level Biology 3.2.9 The Role of Aphids in Spreading Plant Viruses
This short Unit 2 topic is specific to the OxfordAQA course. You need to know that plant viruses cause significant crop losses and reduce the quality of produce, recognise symptoms such as yellowing and distortion of leaves, and explain how vectors such as aphids spread viruses. You also need to describe how aphids feed by inserting their sucking stylets into phloem, why the high pressure in phloem forces sap into the aphid, and how winged females migrate to start new colonies on other plants. It links directly to translocation and mass flow in 3.2.8 and to pathogens in 3.2.1.
What you need to know
- Plant viruses Viruses can cause large losses in crop yield and reduce the quality of produce. Symptoms include yellowing of leaves, leaf distortion and other abnormal growth.
- Vectors A vector is an organism that carries a pathogen from one host to another. Aphids are important vectors of plant viruses.
- Aphid feeding Aphids insert sucking mouthparts called stylets into phloem sieve tubes. Sap in the phloem is under high hydrostatic pressure, so it is forced into the aphid's gut.
- Spread between plants Viruses picked up from an infected plant can be passed to another plant when the aphid feeds again. Winged females migrate to new host plants and start new colonies, spreading viruses further.
- Links to mass flow Aphid stylets have been used as evidence for the mass flow hypothesis, because sap flows out of a cut stylet under pressure and samples taken along the stem show sugar content.
Common mistakes in 3.2.9 The Role of Aphids in Spreading Plant Viruses
- Saying aphids feed on xylem. They feed on phloem sap, which is rich in sugars.
- Saying aphids suck sap actively. Sap is forced into the stylet by the high hydrostatic pressure in the phloem.
- Calling the aphid the pathogen. The virus is the pathogen; the aphid is the vector.
- Ignoring the role of winged females. They migrate to new plants, which is how infections spread across a crop.
Try three 3.2.9 The Role of Aphids in Spreading Plant Viruses exam-style questions
1. Explain why sap enters an aphid's stylet without the aphid needing to suck. (2 marks)
Show the mark scheme answer
Sap in the phloem is under high hydrostatic pressure; so it is forced up the stylet into the gut.
2. Explain how aphids spread viruses between plants. (3 marks)
Show the mark scheme answer
Aphid feeds on phloem of an infected plant and takes up viruses; moves or flies (winged females) to another plant; viruses enter the phloem of the new plant when the aphid feeds.
3. Suggest two effects of a plant virus on a crop. (2 marks)
Show the mark scheme answer
Reduced yield; reduced quality of produce; yellowing of leaves so less photosynthesis; distorted leaves or abnormal growth. (Any 2)
3.2.9 The Role of Aphids in Spreading Plant Viruses FAQs
What does OxfordAQA International A Level Biology 3.2.9 The Role of Aphids in Spreading Plant Viruses cover?
It covers plant virus diseases, their symptoms and effects on crops, and aphids as phloem-feeding vectors.
Which unit is 3.2.9 The Role of Aphids in Spreading Plant Viruses examined in?
It is part of Unit 2, Biological systems and disease, which is examined at International AS. The Unit 5 synoptic paper at A2 can also draw on this content.
How does this topic link to mass flow?
Aphids feed from phloem because sap is under pressure, which is predicted by the mass flow hypothesis. Questions may ask you to use aphid evidence when evaluating mass flow.
