Biological ScienceOrganism DiversityYear 4 Science

Flowers, fruits and seeds, and how seeds travel

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What this lesson covers

Some living things have many young at a time; others have only a few
Some plants can grow a new plant from a piece of themselves
Flowers are where pollination and fertilisation happen, so seeds can form
After fertilisation a fruit grows from the flower and holds the seeds
Seeds store food, need water to sprout, and have parts that help them spread
Sorting seeds by how they are spread

Key idea

Lots of young, or just a few

Some living things have lots of young. A mouse can have a litter of many babies, several times a year.
The wētāpunga, our giant wētā, lays lots of eggs.
Others have only a few young and look after them for a long time.
People usually have one baby at a time. A kiwi lays just one or two very big eggs.

Key idea

New plants from a piece

Some plants can make a new plant without seeds.
Plant a piece of potato that has an 'eye' (a bud), and a new potato plant grows from it.
Put a cut stem of mint in a glass of water, and it grows roots.
A plant grown from a piece is the same as the parent plant.

Key idea

Pollination and fertilisation

Flowers are the parts of a plant made for reproduction.
Pollination is when pollen moves from an anther to a stigma. Bees, birds, wind and other animals carry it.
Tūī and korimako (bellbirds) carry pollen between harakeke (flax) and kōwhai flowers while they drink nectar.
Fertilisation comes next. Inside the flower, the pollen joins with an egg cell in the ovary. Now a seed can form.

Three steps: pollen moves from an anther to a stigma (pollination); a pollen tube grows down to an egg cell in the ovary (fertilisation); the ovary grows into a fruit with seeds inside

Key idea

From flower to fruit

After fertilisation, the petals fall off and the ovary grows into a fruit.
The fruit holds and protects the seeds.
In science, a fruit is any part that grows from a flower and holds seeds. So tomatoes, capsicums and pumpkins are fruits too.

Key idea

Try it: pollination, fertilisation or fruit?

Key idea

What is inside a seed

A seed has a tough coat, a tiny baby plant, and a store of food.
A dry seed waits. When it gets water, it swells up and germinates.
The stored food feeds the young plant until its leaves can make food from sunlight.

Key idea

Spreading seeds

Young plants need their own light, water and space, so seeds must get away from the parent plant. Spreading seeds is called dispersal.
Wings or fluff: the wind carries them, like dandelion and thistle seeds.
Hooks: they catch on fur, feathers or socks, like bidibids.
Fleshy fruit: animals eat it and drop the seeds far away in their droppings. Kererū spread the big seeds of taraire and tawa.
Pods that burst: gorse pods dry out, pop open and flick their seeds away.

Four kinds of seed: a dandelion seed with a fluffy parachute for wind, a bidibid with hooks, a taraire berry eaten by birds, and a gorse pod bursting open

Worked example

Example: how does each seed travel?

Look at the structure of each seed or fruit, then decide how it is spread.

Seed or fruit	Structure	Spread by
Maple seed	A flat wing	Wind
Bidibid	Tiny hooks	Animals' fur
Blackberry	Juicy flesh	Animals eating it
Coconut	Light, air-filled husk	Floating on water

A wing or fluff catches the airwind
Hooks grab onto furanimals carry it
Sweet flesh is foodanimals eat it
Maple: wind. Bidibid: fur. Blackberry: eaten. Coconut: water

Key idea

Try it: how does each seed travel?

Common mistakes

Pollination and fertilisation are the same thing.
Pollination moves pollen to the stigma; fertilisation happens after, when pollen joins an egg cell in the ovary.
Fruits are only sweet things like apples and oranges.
Any part grown from a flower that holds seeds is a fruit, so tomatoes and pumpkins count.
A seed needs soil to start growing.
A seed needs water to germinate; its stored food feeds it at first, so it can sprout on a wet paper towel.

Try it at home

Sprout seeds without soil

You need: 8 dried beans or chickpeas from the pantry, paper towels, 2 clear jars, water, a ruler, a pen and paper

Fold a paper towel into each jar so it lines the side. Wet the towel in the first jar. Leave the second one dry.
Push 4 beans between the towel and the glass in each jar, so you can see them.
Keep the first towel damp. Put both jars on a windowsill.
Each day for 5 days, look at the beans and measure any roots. Write it down.
Look for this: only the wet beans germinate. They grow roots and shoots with no soil, using the food stored inside the seed.

Safety: Raw dried beans can make you sick, so do not eat them, and wash your hands after handling them.

Your turn

Which usually has more young at a time: a mouse or a kiwi?

How can you grow a new potato plant without a seed?

What is it called when pollen moves from an anther to a stigma?

Which part of a flower grows into the fruit?

A seed is covered in tiny hooks. How is it spread?

What does a seed need first, to germinate?

Show answer

1. A mouse. 2. Plant a piece of potato that has an eye. 3. Pollination. 4. The ovary. 5. By catching on animals' fur or feathers. 6. Water.

Summary

Recap

Some living things have many young; others have a few and care for them.
Some plants can grow from a piece, like a potato eye or a stem cutting.
Pollination moves pollen to the stigma; fertilisation in the ovary starts a seed.
The ovary grows into a fruit that holds the seeds.
Seeds store food and need water to germinate.
Wings, hooks, fleshy fruit and bursting pods help seeds spread.

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