AQA GCSE Biology Biology Paper 1 (Foundation), November 2021: Question 3
8 marks · Low Demand difficulty · Short Answer
Identify plant adaptations, defence mechanisms, cell structures, and transport tissues in a cactus plant.
Practise this questionQuestion
Question text
03 A cactus is a plant that lives in a dry environment.
Figure 6 shows part of a cactus plant.
Figure 6
03.1 Give one adaptation shown in Figure 6 that helps to prevent the cactus from being
eaten by animals.
[1 mark]
03.2 A plant may produce poisons that make animals unwell.
What is this type of defence mechanism?
[1 mark]
Tick ( ) one box.
Chemical
Mechanical
Physical 13
03.3 Some desert plants only grow leaves after it has rained.
As soon as the soil dries out, the leaves fall off.
How could the leaves falling off the plant be an advantage to a plant that lives in a dry
*12* environment?
[1 mark]
Tick ( ) one box.
The plant is less likely to reproduce.
The plant will not lose as much water.
The plant will photosynthesise faster.
The stem of a cactus is green.
03.4 What causes the green colour in the stem?
[1 mark]
03.5 What is the advantage to the cactus of having a green stem?
[1 mark]
The stem of a cactus contains many different tissues.
03.6 What name is given to a group of tissues working together?
[1 mark]
Tick ( ) one box.
Organ
Organism
Organ system
03.7 Name one substance transported through the xylem in the stem of the cactus.
[1 mark]
03.8 Name the tissue that transports dissolved sugars through the stem of the cactus.
[1 mark]
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
03.1 (has) spikes / thorns / prickles allow (has a) tough outer layer 1 AO2
4.3.3.2
03.2 chemical 1 AO1
4.3.3.2
03.3 the plant will not lose as much 1 AO2
water 4.2.3.2
03.4 chlorophyll / chloroplasts 1 AO2
4.1.1.2
03.5 to allow it to photosynthesise 1 AO2
or 4.4.1.1
to make sugar / glucose /
carbohydrate / starch
03.6 organ 1 AO1
4.2.1
03.7 water / mineral ions allow named mineral ions 1 AO1
allow minerals / ions 4.2.3.1
4.2.3.2
03.8 phloem (tissue) 1 AO1
4.1.1.3
4.2.3.1
4.2.3.2
Total 8
How to answer it
Cactus Plant Adaptations, Defences & Internal Transport
What this question tests
This 8-mark question assesses foundational recall and application across Plant Organisation (B2) and Plant Defence Mechanisms (B3):
- Structural & chemical plant defences: Distinguishing physical, chemical, and mechanical defences against herbivores.
- Adaptations to arid environments: How surface area reduction minimises transpiration and water loss.
- Photosynthetic structures: Role of chlorophyll/chloroplasts and why desert stems are green.
- Levels of organisation: Defining tissues, organs, and organ systems in plants.
- Vascular transport: Differentiating the roles and contents of xylem and phloem.
Herbivore Defence Adaptation in a Cactus
Identifying an adaptation visible in Figure 6 that deters herbivores
✅ Correct Answer
Any one of the following:
- (has) spikes / thorns / prickles / spines
- (has a) tough outer layer
🧠 Exam Technique
The question says "shown in Figure 6". Always state a feature you can actually observe in the image rather than invisible adaptations like "poisonous sap" or "deep roots".
Classifying Plant Defences
Identifying defence type when a plant produces poisons
✅ Correct Answer
Tick: Chemical
💡 Key Knowledge
- Chemical defences: Antibacterial chemicals, poisons (e.g. digitalis, nicotine).
- Mechanical defences: Thorns, hairy stems, mimicry, curling leaves.
- Physical defences: Cellulose cell wall, tough waxy cuticle, layer of bark / dead cells.
❌ Common Errors
Confusing chemical (substances produced internally to deter pests/pathogens) with physical barriers (barriers that physically block entry like the cuticle).
Leaf Loss Adaptation in Dry Environments
Why shedding leaves when dry helps survival
✅ Correct Answer
Tick: The plant will not lose as much water.
💡 Key Knowledge
Most water is lost from plants via transpiration through stomata located on leaves. Shedding leaves reduces the surface area for evaporation, drastically cutting water loss during dry spells.
❌ Common Errors
Selecting "photosynthesise faster" — shedding leaves reduces surface area for light capture, so photosynthesis slows down; this is a survival trade-off to conserve water.
Green Stems: Pigments and Function
Explaining the cause and advantage of a green stem in a cactus
✅ Correct Answers
- 03.4: chlorophyll (or chloroplasts) [1 mark]
- 03.5: to allow it to photosynthesise OR to make glucose / sugar / starch / carbohydrate [1 mark]
💡 Key Knowledge
- Because cactus leaves are reduced to spines (to stop water loss and deter herbivores), the cactus cannot photosynthesise through broad leaves.
- The stem takes over the job of photosynthesis, which is why it contains chloroplasts with the green pigment chlorophyll.
❌ Common Errors
Writing "to make energy" for 03.5. Examiners will reject "makes energy". Energy cannot be created; photosynthesis makes food/glucose or absorbs light energy.
Levels of Biological Organisation
Identifying what a group of tissues working together forms
✅ Correct Answer
Tick: Organ
💡 Key Knowledge
The biological hierarchy in plants:
- Organelle: Chloroplast, nucleus
- Cell: Palisade cell, root hair cell
- Tissue: Epidermis, mesophyll, xylem, phloem
- Organ: Stem, leaf, root, flower
- Organ system: Shoot system, root system
- Organism: Whole cactus plant
❌ Common Errors
Selecting "Organ system". An organ system is a group of organs working together (e.g. shoot system), not a group of tissues.
Plant Transport: Xylem vs. Phloem
Substances moved by vascular tissues in the stem
✅ Correct Answers
- 03.7 (Xylem): water OR mineral ions (allow minerals / ions, or named ions like nitrates / magnesium) [1 mark]
- 03.8 (Sugars): phloem (tissue) [1 mark]
🧠 Quick Memory Hack
- Xylem transports Water & Minerals (one-way flow, dead hollow tubes). Remember: W-X-Y-Z (Water in Xylem).
- Phloem transports Food (sugars / amino acids by translocation). Remember: Ph sounds like F for Food.
❌ Common Errors
- Stating "glucose" instead of water/minerals in the xylem. Sugars are transported in the phloem as sucrose.
- Confusing the direction: xylem moves upward from roots to leaves/stem; phloem moves bidirectionally (source to sink).
Topics
Biology · B1: Cell Biology · B2: Organisation · B3: Infection and Response · B4: Bioenergetics
Question and mark scheme from the AQA GCSE Biology examination, Biology Paper 1 (Foundation), November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.