Biology · Unit 15

Plant Biology

How plants live and grow

Plants solve every problem an animal solves - getting food, moving materials, reproducing, responding to the world - without moving. The constraint is what makes their solutions interesting.

The unit works through roots, stems and leaves, the transport tissues that move water up and sugars around, the hormones that let a plant bend towards light without a nervous system, and how flowers and seeds handle reproduction at a distance.

This unit breaks down into 20 short steps and 120 questions, starting at difficulty 1 and building to 3. Below you can see exactly what it covers, how the path is structured, and worked examples with explanations.

Steps: 20
Questions: 120
Difficulty: 1-3

What this unit covers

Roots, Stems and Leaves
Xylem and Phloem
Tropisms and Hormones
Flowers and Seeds
Plant Adaptations

Where this fits

Cell Transport and Energy first - photosynthesis is assumed here rather than taught again.

Where people slip

Xylem and phloem are easy to swap. Xylem carries water upward and is made of dead cells; phloem carries dissolved sugars in either direction and has to be alive to do it.

How the unit is structured

Plant Biology runs as 20 short steps that unlock in order. 15 are practice rounds and 5 are challenge rounds that pull together everything before them. Questions start at difficulty 1 and climb to 3 as you progress.

Step 1 · easierStep 20 · harder

Challenge rounds

Example questions

30 real questions from this unit, with the answer and the reason behind it, grouped by what they practise. There are 120 in the unit altogether.

Flowers and Seeds

Fill the blankLevel 2
1. Conifers are gymnosperms whose 'naked' seeds are not enclosed in a fruit but are usually carried in woody ____.
- conescorrect
- fruits
- pods
- nodules
Gymnosperm means naked seed; conifers bear their seeds on the scales of cones rather than inside fruits.
Match the pairsLevel 2
2. Match each flower part to its job.
Answer: Anther = Makes pollen; Stigma = Receives pollen; Ovary = Contains the ovules; Petal = Attracts insects
The anther makes pollen, the stigma receives it, the ovary holds the ovules, and petals attract pollinators.
Multiple choiceLevel 2
3. Which feature is typical of a wind-pollinated flower?
- Feathery stigmas and light pollencorrect
- Large, brightly coloured petals
- Sweet nectar to attract bees
- A strong, sticky scent
Wind-pollinated flowers make lots of light pollen and have feathery stigmas to catch pollen from the air, so they do not need showy petals.
Odd one outLevel 2
4. Which of these is NOT a way that seeds are spread (dispersed)?
- By wind
- By animals
- By water
- By osmosiscorrect
Seeds are dispersed by wind, animals and water - osmosis is how water moves into cells, not a way seeds spread.
Sequence recallLevel 2
5. Remember the order of a flowering plant's life cycle.
Answer: Seed -> Germination -> Seedling -> Flowering plant -> Pollination -> New seeds form
A seed germinates into a seedling that grows into a flowering plant; after pollination, new seeds form to begin the cycle again.
Fact or fibLevel 3
6. In mosses, the green leafy plant you see is the haploid gametophyte generation.
Answer: True
In bryophytes the dominant, visible plant is the haploid gametophyte, with the sporophyte growing on top of it.

Plant Adaptations

Multiple choiceLevel 2
7. Why do plants need to take in nitrate from the soil?
- To make proteins for healthy growthcorrect
- To make chlorophyll green
- To store water in the roots
- To attract insects to the flowers
Nitrate provides nitrogen, which plants use to build proteins needed for healthy growth.
Odd one outLevel 2
8. Three of these are physical (mechanical) plant defences. Which one is the odd item out?
- Bitter alkaloidscorrect
- Thorns
- Stinging hairs
- Thick bark
Thorns, stinging hairs and thick bark are physical defences; bitter alkaloids are a chemical defence.
Picture questionLevel 2
9. 🌵 How is this desert plant adapted to survive with very little water?
- It has spines instead of leaves and a thick, waxy stem that stores water and cuts water loss
- It has huge, flat leaves to lose water quickly
- It has no roots, so it never takes in water
- It keeps all its stomata wide open during the hot day
A cactus reduces water loss with spine-like leaves and a thick, waxy stem that also stores water.
Spell itLevel 2
10. In cacti, the leaves are reduced to sharp ____ to cut water loss and deter herbivores; the stem does the photosynthesis.
Answer: spines
Reducing leaves to spines lowers the surface area available for transpiration, while the swollen green stem carries out photosynthesis.
Choose all that applyLevel 3
11. Which of the following are xerophytic adaptations that reduce water loss? (Select all that apply)
- Leaves reduced to spines to lower surface areacorrect
- Rolled leaves that trap a moist layer of aircorrect
- A thin cuticle with many exposed stomata
- Hairs (trichomes) that trap humid air near the stomatacorrect
Reduced leaves (spines), rolled leaves and hairs all cut transpiration; a thin cuticle with many exposed stomata would increase water loss.
Fill the blankLevel 3
12. CAM plants fix CO2 at night and store it as ____ acid, then release it for the Calvin cycle during the day.
- maliccorrect
- citric
- amino
- nitric
CAM plants store night-fixed carbon as malic acid in their vacuoles, releasing CO2 for photosynthesis by day.

Roots, Stems and Leaves

Build the sentenceLevel 1
13. Build the sentence about what a stem does.
Answer: The stem holds the plant upright
The stem supports the plant, holding its leaves and flowers up toward the light.
Fill the blankLevel 1
14. Root ____ cells have a long, thin shape that gives a large surface area for absorbing water.
- haircorrect
- guard
- palisade
- muscle
Root hair cells extend into the soil, giving a large surface area to absorb water and minerals quickly.
Choose all that applyLevel 2
15. Which features help a leaf carry out photosynthesis efficiently? (Select all that apply.)
- A large, flat surface to capture sunlight
- Being thin so gases diffuse quicklycorrect
- A network of veins to bring water and carry away sugarscorrect
- A thick, dark layer that blocks out sunlight
Leaves are broad, flat and thin with veins, so they capture light well and exchange gases and materials quickly.
Fact or fibLevel 2
16. A waxy cuticle on the surface of a leaf helps reduce water loss.
Answer: True
The waterproof waxy cuticle cuts down evaporation of water from the leaf surface.
Guess the numberLevel 2
17. A cut tree trunk shows 24 clear annual growth rings. About how old is the tree in years?
Answer: 24 years
Each annual ring represents one year of growth, so a trunk with 24 rings is about 24 years old.
Match the pairsLevel 3
18. Match each mineral to the deficiency symptom a plant shows when it runs short of it.
Answer: Potassium = Yellowing and spots around the leaf edges; Phosphate = Poor root growth and purple-tinged leaves; Calcium = Weak, distorted new growth at the tips; Iron = Yellowing of the youngest leaves
Different minerals cause distinct deficiency signs, which growers use to diagnose and correct nutrient problems.

Tropisms and Hormones

Fact or fibLevel 1
19. A plant shoot grows toward a light source.
Answer: True
Shoots are positively phototropic, bending toward light so the leaves can capture more energy.
Multiple choiceLevel 1
20. What is phototropism?
- A plant's growth response to the direction of lightcorrect
- A plant's growth response to gravity
- The loss of water from a plant's leaves
- The transport of sugars in a plant
Phototropism is when a plant grows in response to light - shoots usually grow toward it.
Fill the blankLevel 2
21. A plant's growth response to gravity is called ____.
- gravitropismcorrect
- phototropism
- translocation
- pollination
Gravitropism (also called geotropism) is growth in response to gravity - roots grow down and shoots grow up.
Odd one outLevel 2
22. Which of these is NOT a plant growth regulator?
- Insulincorrect
- Auxin
- Gibberellin
- Cytokinin
Insulin is an animal hormone that controls blood glucose; auxin, gibberellin and cytokinin are plant growth regulators.
Picture questionLevel 2
23. 🍌 Which gaseous plant hormone promotes the ripening of fruits such as this banana?
- Ethylenecorrect
- Auxin
- Cytokinin
- Abscisic acid
Ethylene is a gas that accelerates fruit ripening, which is why one ripe fruit can trigger ripening in others nearby.
Match the pairsLevel 3
24. Match each plant hormone to its main effect.
Answer: Auxin = Cell elongation and phototropism; Gibberellin = Stem elongation and seed germination; Ethylene = Fruit ripening; Abscisic acid = Stomatal closure in drought
Auxin drives elongation and phototropism, gibberellin promotes germination, ethylene ripens fruit and abscisic acid closes stomata in drought.

Xylem and Phloem

Fact or fibLevel 1
25. Transpiration happens faster on a hot, windy day than on a cool, still day.
Answer: True
Heat and wind speed up evaporation from the leaves, so transpiration is faster.
Fill the blankLevel 1
26. The loss of water vapour from a plant's leaves is called ____.
- transpirationcorrect
- translocation
- respiration
- germination
Transpiration is the evaporation and loss of water vapour, mainly through the stomata in the leaves.
Multiple choiceLevel 1
27. What does xylem tissue carry, and in which direction?
- Water and minerals upward, from roots to leaves
- Sugars downward, from leaves to roots
- Oxygen from the air into the roots
- Pollen from the anther to the stigma
Xylem vessels transport water and dissolved minerals up from the roots to the rest of the plant.
Build the sentenceLevel 2
28. Arrange the words to describe how water is drawn through a plant.
Answer: transpiration pulls water up the xylem
Transpiration from the leaves creates the pull that lifts the cohesive water column up the xylem.
Guess the numberLevel 2
29. Roughly what percentage of the water a plant absorbs is lost again through transpiration?
Answer: 99 %
Plants lose around 99% of the water they take up through transpiration, using only about 1% for photosynthesis.
Choose all that applyLevel 3
30. Which features of mature xylem vessels help them transport water efficiently? (Select all that apply)
- They are dead and empty, forming continuous open tubes
- Their walls are strengthened with lignincorrect
- They contain many mitochondria to actively pump water
- They have pits that allow water to move sideways between vesselscorrect
Xylem vessels are dead, hollow, lignified tubes with pits, so water flows through them with little resistance; they do not use mitochondria to move water.

Where these questions come from. Each unit starts as a plan of the concepts it should cover and the difficulty it should span. Questions are written against that plan with AI assistance, then checked by a validator that rejects anything without a single defensible answer, an explanation, or plausible wrong options. How we write questions sets out the whole process, and corrections are fixed in the bank and reach the site and the app the same day.

How you practise

This unit mixes 17 different question formats, so you are recalling and applying rather than recognising the same layout every time.

Build the sentence
Choose all that apply
Fact or fib
Fill the blank
Guess the number
Listen and choose
Match the pairs
Multiple choice
Odd one out
Picture question
Put in order
Sequence recall
Sort into groups
Spell it
Tap the pairs
True or false
Type the answer

Practise Plant Biology

120 questions across 20 steps. Start with step one and crawl at your own pace.

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Read about Plant Biology

Explainers from our blog on what this unit covers. Each one ends with real questions from the bank.

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