Reproduction in flowering plants

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Apuntes de la lección

Big idea: how flowering plants make new plants

Big idea (key concept): Change. A flower changes as a plant reproduces. Pollen is carried to a flower, the ovule becomes a seed, the ovary becomes a fruit, and the seed grows into a new plant.
Related concept: Interaction. Plants cannot move, so they depend on interactions with wind, insects and other animals to carry their pollen and seeds, and on water, oxygen and warmth to start growing.
Global context: Globalization and sustainability. Many of the world's food crops need insects to pollinate them. If pollinators such as bees decline, food supplies around the world are at risk, so protecting them matters everywhere.
Flowering plants reproduce sexually. A male sex cell (inside a pollen grain) joins with a female sex cell (inside an ovule) to make a seed. The new plant is different from both parents.
The whole life cycle is: flower, pollination, fertilisation, seed and fruit, dispersal, germination, new plant.

A bee covered in pollen on a flower

The parts of a flower

The flower is the reproductive organ of a flowering plant.
Sepals are small green leaf-like parts that protect the flower while it is still a bud.
Petals are often large, bright and scented in insect-pollinated flowers, to attract insects.
The stamen is the male part. The anther makes pollen grains, which contain the male sex cells, and the filament holds the anther up.
The carpel is the female part. The stigma is the sticky top that catches pollen, the style is the stalk that holds it up, and the ovary at the base contains the ovules. Each ovule holds a female sex cell, the ovum (egg cell).
Many flowers have both stamens and carpels, but some have only one kind.

The parts of an insect-pollinated flower

Pollination: getting pollen to a stigma

Pollination is the transfer of pollen from an anther to a stigma. It is not the same as fertilisation.
In self-pollination the pollen lands on a stigma of the same plant. In cross-pollination it lands on a flower of a different plant of the same species. Cross-pollination mixes genes, so the offspring show more variation.
Insect-pollinated flowers have bright, scented petals, make sugary nectar as a reward, and have sticky or spiky pollen that clings to an insect's body. The stigma is inside the flower where the insect brushes against it.
Wind-pollinated flowers have small, dull petals and no nectar or scent. Their anthers hang outside the flower and their large, feathery stigmas catch pollen from the air. They make huge amounts of light, smooth pollen, because most of it never reaches a stigma.
Grasses and maize are wind-pollinated. Most garden flowers are pollinated by insects such as bees, hoverflies and butterflies.

How a wind-pollinated flower is built

Fertilisation, seeds and fruits

When a pollen grain lands on a stigma of the right species, it grows a pollen tube down the style towards the ovary.
The tube enters an ovule through a tiny gap called the micropyle. The male nucleus travels down the tube.
Fertilisation happens when the male nucleus fuses with the female nucleus inside the ovum. The fertilised cell is a zygote. It divides to make an embryo.
After fertilisation, each ovule develops into a seed. The ovary develops into a fruit, which protects the seeds and often helps spread them. The petals and stamens wither and fall away.
A seed has three main parts: a tiny embryo (a new plant), a food store, and a tough seed coat that protects it.

A pollen tube growing to the ovule

Seed dispersal: moving away from the parent

Seed dispersal is the spreading of seeds away from the parent plant.
It helps because seedlings that grow far from the parent do not compete with it, or with each other, for light, water and minerals. It also lets the species reach new places.
Wind: light seeds with fluffy parachutes (dandelion) or wings (sycamore and maple) are carried a long way.
Animals: fruits with hooks or spines (burdock) stick to fur. Juicy fruits are eaten, and the seeds pass through the animal and are dropped in its droppings, often far away.
Explosive: pods such as peas and gorse dry out, split and fling their seeds out.
Water: light, waterproof fruits such as coconuts float across seas. Heavy fruits such as acorns simply fall to the ground.

Ways seeds are dispersed

Think like a scientist: what do seeds need to germinate?

Germination is when a seed starts to grow into a seedling.
Seeds need water (to swell and to let chemical reactions start), oxygen (for respiration, which releases energy for growth) and a suitable temperature (enzymes work best when it is warm enough, but not too hot). Most seeds do not need light or soil to germinate.
The first root emerges, then the shoot. Until its leaves open and start photosynthesis, the seedling lives on the food store inside the seed.
To test one factor, change only that factor. In the set-up shown, the tube with no water, the tube with boiled water and oil (no oxygen) and the tube in the cold each differ from the first tube in one way only.
The independent variable is the one you change and the dependent variable is the one you measure, such as the number of seeds that germinate. Repeating the test with more seeds makes the results more reliable.
Inquiry task: plan an investigation into whether temperature affects how many cress seeds germinate. Choose at least four temperatures, say what you will measure and when, name three variables you will control, and explain how you will decide which temperature is best and how reliable your result is.

Testing what seeds need to germinate

Diapositivas

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Preguntas de práctica

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1.Which part of a flower makes pollen?
Easy
- AThe stigma
- BThe ovary
- CThe anther
- DThe sepal
2.Which part of a flower catches pollen?
Easy
- AThe stigma
- BThe anther
- CThe filament
- DThe petal
3.Where are the ovules found in a flower?
Easy
- AOn the anther
- BOn the sepals
- CInside the filament
- DInside the ovary
4.Which part of a flower is the male part?
Easy
- AThe carpel
- BThe stamen
- CThe ovary
- DThe style
5.What is the main job of the sepals?
Easy
- ATo make the pollen grains
- BTo protect the flower bud
- CTo catch the pollen grains
- DTo attract the insects
6.What is pollination?
Easy
- AThe joining of a male and a female nucleus
- BThe spreading of seeds away from a plant
- CThe growth of a seed into a seedling
- DThe transfer of pollen from an anther to a stigma
7.Why do insect-pollinated flowers have brightly coloured petals?
Easy
- ATo attract insects
- BTo protect the seeds
- CTo make pollen
- DTo catch the wind
8.Insects can carry pollen from one flower to another.
Easy
True or false?

Más preguntas

9.Wind-pollinated flowers usually have large, brightly coloured petals.
Easy
True or false?
10.What does the ovule become after fertilisation?
Easy
- AA fruit
- BA petal
- CA seed
- DA pollen grain
11.What does the ovary become after fertilisation?
Easy
- AA seed
- BA stigma
- CA flower bud
- DA fruit
12.Dandelion seeds have a fluffy parachute. How are they dispersed?
Easy
- ABy water
- BBy the wind
- CBy explosion
- DBy animals eating them
13.Burdock fruits have small hooks. How are they dispersed?
Easy
- ABy floating on water
- BBy blowing in the wind
- CBy sticking to animal fur
- DBy bursting open
14.Which of these does a seed need in order to germinate?
Easy
- AWater
- BSunlight
- CSoil
- DFertiliser
15.Match each part of a flower to its job.
Easy
- Anther
- Stigma
- Petal
- Ovary
- Contains the ovules
- Attracts insects
- Makes pollen
- Catches pollen
16.Match each plant to the way its seeds are dispersed.
Easy
- Coconut
- Pea pod
- Sycamore
- Burdock
- Wings carry it on the wind
- Floats on water
- Hooks stick to fur
- Pod bursts and flings seeds
17.Put the stages of a flowering plant's life cycle in order.
Easy
- Adult plant
- Seed
- Flower
- Seedling
- Germination
18.Complete the sentence.
Easy
Pollen grains are made in the ____ of the flower.
19.Complete the sentence.
Easy
A ____ tube grows from a pollen grain down the style.
20.What is the difference between pollination and fertilisation?
Medium
- APollination moves pollen; fertilisation joins two nuclei
- BPollination makes seeds; fertilisation makes pollen
- CPollination happens in the ovary; fertilisation on the petals
- DPollination is done by insects; fertilisation by the wind
21.Which feature is an adaptation for wind pollination?
Medium
- ASweet nectar at the base of the petals
- BLarge, scented petals
- CAnthers that hang outside the flower
- DSticky, spiky pollen grains
22.Why do wind-pollinated plants make huge amounts of pollen?
Medium
- AInsects eat most of the pollen
- BMost of the pollen never lands on a stigma
- CLarge amounts attract insects
- DEach pollen grain is too heavy to travel
23.Why is the pollen of insect-pollinated flowers often sticky or spiky?
Medium
- ASo it floats away on the wind
- BSo it dissolves in nectar
- CSo it can grow a pollen tube
- DSo it clings to the insect's body
24.What is the job of nectar in an insect-pollinated flower?
Medium
- AIt carries pollen down the style to the ovary
- BIt stores food for the growing embryo
- CIt is a food reward for visiting insects
- DIt protects the ovules from being eaten
25.Why is cross-pollination useful to a species?
Medium
- AIt produces offspring with more variation
- BIt produces offspring that are identical to the parents
- CIt lets a plant make seeds without pollen
- DIt lets seeds travel further from the plant
26.Through which part of the carpel does the pollen tube grow?
Medium
- AThe filament
- BThe sepal
- CThe anther
- DThe style
27.What fuses together at fertilisation in a flowering plant?
Medium
- AAn anther and a stigma
- BA male nucleus and a female nucleus
- CA seed and a fruit
- DA petal and a sepal
28.Which of these is found inside a seed?
Medium
- AA stigma and a style
- BAn embryo and a food store
- CAn anther and a filament
- DA petal and a sepal
29.How does a seedling get its energy before its first leaves open?
Medium
- AFrom photosynthesis in the root
- BFrom nutrients in the pollen
- CFrom energy stored in the fruit
- DFrom the food store in the seed
30.Why is it an advantage for seeds to be dispersed away from the parent plant?
Medium
- AThere is less competition for light and water
- BThe parent plant can then make more pollen
- CThe seeds no longer need water to germinate
- DThe seeds can turn into fruits more quickly
31.Which of these are needed for seeds to germinate? (select all that apply)
Medium
- AWater
- BOxygen
- CA suitable temperature
- DBright light
- EFertiliser in the soil
32.Which of these are adaptations of an insect-pollinated flower? (select all that apply)
Medium
- AScented petals
- BNectar
- CBrightly coloured petals
- DLarge feathery stigmas hanging outside
- EAnthers on long filaments outside the flower
33.Fertilisation happens as soon as pollen lands on the stigma.
Medium
True or false?
34.All seeds need light to germinate.
Medium
True or false?
35.Animals can spread seeds without carrying them on their fur.
Medium
True or false?
36.Match each part of the flower to what it becomes after fertilisation.
Medium
- Ovule
- Ovary
- Zygote
- Fruit
- Embryo
- Seed
37.Put these events in the correct order.
Medium
- The male nucleus fuses with the ovum nucleus
- A pollen grain lands on the stigma
- The ovule develops into a seed
- A pollen tube grows down the style
38.Complete the sentence.
Medium
The cell formed when a male nucleus fuses with a female nucleus is called a ____.
39.A student sets up four tubes of cress seeds. Tube A has water and air at 20° C, tube B has boiled water with oil on top (no oxygen) at 20° C, tube C has dry cotton wool and air at 20° C, and tube D has water and air at 4° C. Which two tubes should be compared to find out if seeds need oxygen?
Medium
- AA and C
- BA and D
- CA and B
- DC and D
40.A student tests how temperature affects germination of cress seeds. What is the dependent variable?
Medium
- AThe temperature of each tube
- BThe type of seed used
- CThe amount of water in each tube
- DThe number of seeds that germinate
41.
Twenty cress seeds were kept at each temperature for five days.
Temperature (degrees C) Seeds germinated (out of 20)
5 2
15 11
25 18
35 9
What percentage of the seeds germinated at 25° C?
Medium
42.
Twenty cress seeds were kept at each temperature for five days.
Temperature (degrees C) Seeds germinated (out of 20)
5 2
15 11
25 18
35 9
Which conclusion is best supported by these results?
Hard
- ASeeds cannot germinate at any temperature above 25° C
- BGermination was highest at 25° C of those tested
- CGermination always rises as the temperature rises higher
- D25° C is the best temperature for every kind of seed
43.In the investigation above, only one dish of 20 seeds was used at each temperature. What is the best way to improve the reliability of the results?
Hard
- AUse a different type of seed at each temperature
- BCount the germinated seeds only on the first day
- CRepeat each temperature and calculate a mean
- DUse extra temperatures but still only one dish each
44.Why would a fall in the number of bees worry farmers who grow fruit?
Hard
- AMany fruit crops need insects to carry their pollen
- BBees eat the fruit before it has ripened
- CFruits can only form from wind-pollinated flowers
- DBees help the seeds to germinate in the soil
45.A plant that always pollinates itself produces seedlings that are very similar to each other. Why is this a disadvantage?
Hard
- AA new disease could harm all of them
- BThey will not be able to grow roots
- CThey will produce no pollen at all
- DThey will need more water than other plants
46.A plant has small green flowers with long feathery stigmas, and anthers that dangle outside the flower on thin filaments. How is it most likely pollinated?
Hard
- ABy bees
- BBy butterflies
- CBy the wind
- DBy birds
47.Which statements about fruits are correct? (select all that apply)
Hard
- AThey develop from the ovary
- BThey contain the seeds
- CThey can help seeds to be dispersed
- DThey develop from the anther
- EThey form before fertilisation
48.A grass flower does not need large, scented petals.
Hard
True or false?
49.Describe what happens from the moment a pollen grain lands on a stigma until fertilisation takes place.
Hard
50.Give two differences between an insect-pollinated flower and a wind-pollinated flower, and explain why each helps.
Hard
51.Explain why seed dispersal is important for a plant species. Give one way a seed can be dispersed.
Hard
52.Plan a fair test to find out whether seeds need water to germinate. Say what you would change, what you would measure and two things you would keep the same.
Hard

Apuntes de repaso

## The big idea - Flowering plants reproduce **sexually** and the flower changes as it makes seeds (**Change**, **Interaction**). Pollinators matter for food supplies around the world. ## Flower parts - **Stamen** (male): **anther** and **filament**. **Carpel** (female): **stigma**, **style** and **ovary** with **ovules**. **Petals** attract insects; **sepals** protect the bud. ## Pollination - Pollen moves from anther to stigma. **Cross-pollination** gives more variation. - **Insect-pollinated**: bright, scented petals, nectar, sticky pollen. **Wind-pollinated**: small dull petals, hanging anthers, feathery stigmas, lots of light pollen. ## Fertilisation and seeds - A **pollen tube** grows down the style. The male nucleus **fuses** with the female nucleus in the ovum to make a **zygote**. - **Ovule** becomes **seed**; **ovary** becomes **fruit**. ## Dispersal and germination - Dispersal (wind, animals, water, explosion) reduces competition and spreads the species. - Seeds need **water**, **oxygen** and **warmth** to germinate, and use their food store until leaves can photosynthesise. - Investigations: change one variable, measure one, control the rest, repeat.

Stamen: The male part of a flower, made of an anther and a filament.
Carpel: The female part of a flower, made of a stigma, style and ovary.
Anther: The part of the stamen that makes pollen grains.
Stigma: The sticky top of the carpel that catches pollen.
Ovary: The part of the carpel that contains the ovules and becomes the fruit.
Ovule: A structure in the ovary that contains a female sex cell and becomes the seed.
Pollination: The transfer of pollen from an anther to a stigma.
Cross-pollination: Pollination between flowers on different plants of the same species.
Pollen tube: A tube that grows from a pollen grain down the style to the ovule.
Fertilisation: The fusing of a male nucleus with a female nucleus.
Zygote: The cell formed when a male and female nucleus fuse.
Seed: The structure that forms from a fertilised ovule, containing an embryo and a food store.
Fruit: The structure that forms from the ovary and holds the seeds.
Seed dispersal: The spreading of seeds away from the parent plant.
Germination: The start of growth of a seed into a seedling.
Nectar: A sugary liquid made by flowers to attract insects.

Tarjetas

Name the male parts of a flower.

The stamen: the anther, which makes pollen, and the filament that holds it up.

Name the female parts of a flower.

The carpel: the stigma, the style and the ovary, which contains the ovules.

What do petals and sepals do?

Petals attract insects. Sepals protect the flower bud.

What is pollination?

The transfer of pollen from an anther to a stigma.

What is cross-pollination and why is it useful?

Pollen moves between flowers on different plants. It gives offspring with more variation.

Give three features of an insect-pollinated flower.

Bright scented petals, nectar, and sticky or spiky pollen.

Give three features of a wind-pollinated flower.

Small dull petals, anthers hanging outside, and large feathery stigmas.

Why do wind-pollinated plants make so much pollen?

Most of it never lands on a stigma.

What is the difference between pollination and fertilisation?

Pollination moves pollen to a stigma. Fertilisation is the fusing of the male and female nuclei.

How does the male nucleus reach the ovum?

A pollen tube grows down the style, and the male nucleus travels down it into the ovule.

What is a zygote?

The cell formed when a male nucleus fuses with a female nucleus.

What do the ovule and ovary become?

The ovule becomes the seed and the ovary becomes the fruit.

What are the three main parts of a seed?

An embryo, a food store and a seed coat.

Why do plants disperse their seeds?

To reduce competition for light, water and minerals and to reach new places.

Name four ways seeds are dispersed.

Wind, water, animals (on fur or eaten) and explosive pods.

What do seeds need to germinate?

Water, oxygen and a suitable temperature.

How does a seedling feed before it has leaves?

It uses the food store inside the seed.

Why are pollinators important for people?

Many food crops need insects to carry pollen so they can make fruit and seeds.

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Temperature (degrees C)	Seeds germinated (out of 20)
5	2
15	11
25	18
35	9

Temperature (degrees C)	Seeds germinated (out of 20)
5	2
15	11
25	18
35	9