Example 1: a percentage
16 out of 25 seeds germinated. What percentage is this?
- 16 ÷ 25 = 0.64.
- 0.64 × 100 = 64%.
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IB DemystifiedMYP Sciences
Plant reproduction
Every mango, grain of wheat and cotton boll begins with a flower. Flowers attract insects or catch the wind, seeds travel on animals and breezes, and young plants burst from the soil when conditions are right.
Recommended for MYP 1 · About 3 lessons · Criteria A, B, C and D
On this page
- Learning objectives
- Before you start
- Key vocabulary
- Understanding the ideas
- From flower to new plant
- Plant reproduction in the real world
- Worked examples
- Assessment tips
- Check your understanding
- Practice questions
- Investigation
- Criterion-linked questions
- Challenge questions
- Topic check
- Review your mistakes
- Your progress
Learning objectives
By the end of this topic you should be able to:
- identify the parts of a flower and describe their jobs
- explain pollination by insects and wind
- describe fertilisation and how seeds and fruits form
- explain seed dispersal and the conditions for germination
- compare sexual and asexual reproduction in plants
- discuss protecting pollinators and plant varieties
Before you start
You will use these skills. If any feel shaky, review them first.
- cells and life processes (see Characteristics and classification)
- food chains (see Ecosystems, food chains and food webs)
- percentages
Key vocabulary
- Stamen
- The male part of a flower: anther and filament.
- Carpel
- The female part: stigma, style and ovary.
- Pollination
- Transfer of pollen from an anther to a stigma.
- Fertilisation
- Joining of a male and a female sex cell in an ovule.
- Seed dispersal
- Spreading seeds away from the parent plant.
- Germination
- The start of growth of a seed into a new plant.
Understanding the ideas
-
What is it?
Flowers are the reproductive organs of many plants. Anthers make pollen, which carries the male sex cells; ovules inside the ovary contain the female sex cells.
-
Why does it happen?
In pollination, insects or the wind carry pollen to a stigma. A pollen tube grows down to an ovule, and the sex cells join: fertilisation. Ovules become seeds and the ovary becomes a fruit, which helps disperse the seeds by wind, animals, water or explosion.
-
How do we know?
Seeds germinate when they have water, warmth and oxygen; experiments show most do not need light to germinate. Many plants can also reproduce asexually, from runners, bulbs or cuttings, making identical copies.
-
Why does it matter?
Farmers depend on pollinators and good seeds. Protecting bees and storing seeds in seed banks helps keep food supplies secure.
-
What does it connect to?
Plant reproduction links to cells, food webs, inheritance, variation and evolution later in the course.
From flower to new plant
- Pollination: pollen moves from an anther to a stigma (by insects or wind).
- Fertilisation: a pollen tube grows to an ovule, and the sex cells join.
- Seed and fruit: the ovule becomes a seed; the ovary becomes a fruit.
- Dispersal: seeds are spread by wind, animals, water or explosion.
- Germination: with water, warmth and oxygen, the seed grows into a new plant.
Plant reproduction in the real world
Farmers keep beehives near orchards to improve fruit yields. Mango and citrus growers use grafting to copy their best trees. Seed banks around the world store seeds of wheat, rice and wild plants in case varieties are lost.
Worked examples
Example 2: dispersal
Coconuts are large, waterproof and float. How are they dispersed?
- They can float on sea water.
- They are dispersed by water, reaching new beaches far away.
Assessment tips
Plant reproduction questions often use flower diagrams and germination experiments. Expect to:
- Label flower parts and state their jobs.
- Explain pollination, fertilisation and dispersal.
- Analyse germination and dispersal data.
- Plan fair tests with seeds.
Common mistakes: confusing pollination with fertilisation; saying seeds need light to germinate; mixing up the male and female parts; and forgetting that a fruit develops from the ovary.
Check your understanding
Quick questions on the ideas above. Try each one before using a hint.
Practice questions
Investigation: dissecting a flower
Partially guided investigation · about 40 minutes · pairs
- Research question
- Can you find and identify all the parts of a real flower, and count its stamens and carpels?
- Scientific background
- Flowers contain male parts (stamens) and female parts (carpels). Their number and shape help identify the plant and show how it is pollinated.
- Hypothesis
- Write your own prediction, with a scientific justification.
- Variables
- Identify your independent, dependent and control variables, and explain how you will control them.
- Apparatus
- Large simple flowers (such as lilies or hibiscus), tweezers, hand lens, white card, sticky tape, plastic knife.
- Method
- Remove the sepals and petals one at a time and tape them to the card in order.
- Remove the stamens, count them, and look at the anthers and pollen with the hand lens.
- Cut the ovary open carefully to see the ovules.
- Label every part and note whether the flower is likely to be insect- or wind-pollinated.
Safety. Some pollen can cause allergies and stain clothes; lily pollen is poisonous to cats. Wash hands afterwards and take care with knives.
Then evaluate: which features of your flower suggest how it is pollinated?
Criterion-linked questions
Criterion B: inquiring and designing
Criterion C: processing and evaluating
Criterion D: reflecting on the impacts of science
Challenge questions
Harder problems in unfamiliar contexts. Plan before you calculate.
Topic check
Five questions picked at random from the whole topic. Take a new set whenever you like.
Review your mistakes
Questions you got wrong on this device appear here so you can try them again. Answer one correctly and it leaves the list.
Your progress
Tracked separately for each skill, on this device only.
| Skill | Correct | Status |
|---|