Aqa Igcse Biology. Key Facts Chapter 9

Front 1

What can carry out photosynthesis?

Back 1

Green plants and algae

Front 2

What inside the plant absorbs light energy for photosynthesis?

Back 2

Chlorophyll in chloroplasts

Front 3

What is the word equation for photosynthesis?

Back 3

Carbon dioxide + water --> glucose + oxygen

Front 4

What is the symbol equation for photosynthesis?

Back 4

6CO2 + 6H2O --> C6H12O6 + 6O2

Front 5

How would you use a chemical test to see if photosynthesis has occurred in a leaf?

Back 5

Use iodine solution to test for starch, it will turn blue-black in the presence of starch

Front 6

What is a limiting factor?

Back 6

Anything that stops the rate of photosynthesis above a certain level

Front 7

What are the limiting factors for photosynthesis?

Back 7

Shortage of light

low temperatures

shortage of carbon dioxide

Front 8

Why is shortage of light a limiting factor for photosynthesis?

Back 8

Because light provides the energy for photosynthesis

Front 9

Why is low temperature a limiting factor for photosynthesis?

Back 9

Enzymes don't work effectively in the cold

Front 10

Why is shortage of carbon dioxide a limiting factor for photosynthesis?

Back 10

Carbon dioxide is needed for the reaction

carbon dioxide may be limited in enclosed spaces

Front 11

How can we artificially control limiting factors?

Back 11

Greenhouses and polytunnels are used to increase crop yields

Front 12

How might glucose from photosynthesis be used?

Back 12

Converted into insoluble starch for storage in organs

used for respiration

converted into fats and oils for storage

used to produce cellulose which strengthens cell walls

used to produce proteins

Front 13

What do plant and algal cells need as well as glucose in order to produce proteins?

Back 13

A supply of mineral ions (e.g. nitrate ions)

Front 14

How are carnivorous plants adapted to live in nutrient-poor soil?

Back 14

They obtain nitrates by digesting animal protein (e.g. the Venus flytrap)

Front 15

How do gasses diffuse in and out of leaves?

Back 15

Through the stomata

Front 16

How are the stomata controlled?

Back 16

By the guard cells

Front 17

Which gases diffuse in and out of leaves?

Back 17

Oxygen and carbon dioxide

Front 18

How is water lost from plants?

Back 18

Through the stomata by evapouration

Front 19

How are leaves adapted for gas exchange?

Back 19

Flat and thin to provide a short diffusion distance.

Air spaces allow for gas exchange

Front 20

How are roots adapted for the absorption of water and mineral ions

Back 20

Root hair cells increase the surface area

Front 21

What will happen if plants lose water faster than they can absorb it?

Back 21

The stomata close to prevent wilting

Front 22

What is transpiration?

Back 22

The loss of water from the surface of plant leaves

Front 23

What is the transpiration stream?

Back 23

The movement of water through the plant

Front 24

When is evaporation most rapid?

Back 24

In hot, dry or windy conditions

Front 25

What will happen to reduce water loss in the plant?

Back 25

Guard cells will close stomata

The plant may wilt, the leaves hang down and this decreases the surface area for transpiration

Front 26

What does the xylem tissue do?

Back 26

Transports water and mineral ions from the roots up

Front 27

What does Phloem tissue do?

Back 27

Carries dissolved sugars from leaves to the rest of the plant

Front 28

What are plant responses to light, gravity and moisture known as?

Back 28

Tropisms

Front 29

What is phototropism?

Back 29

Plant shoots grow towards the light so that they can photosynthesise

Front 30

What is gravitropism (geotropism)?

Back 30

Roots grow down towards gravity

Front 31

What is hydrotropism?

Back 31

Roots grow towards water

Front 32

What is the hormone that controls phototropism and geotropism?

Back 32

Auxin

Front 33

What is the result of unequal distribution of auxin?

Back 33

unequal growth, the root or shoot bends

Front 34

What happens if light only shines onto a shoot from one side?

Back 34

The auxin responds by diffusing away from the light, therefore the side of the shoot in the shade has more auxin, so grows faster, causing the shoot to bend towards the light

Front 35

How can plant hormones be used in horticulture and agriculture?

Back 35

Growth hormones can be used as weed killers or to stimulate growth.

Herbicides are used to kill unwanted plants.

When cuttings are taken from plants, hormones can be used to encourage roots to grow before planting.

Front 36

What happens during pollination?

Back 36

The anther produces the male gametes (pollen grains). The pollen grains are carried by insect or wind to the carpel. The pollen grains attach to the stigma (on top of the style). Pollination occurs when the pollen attaches to the stigma

Front 37

What is the carpel made of?

Back 37

The stigma, style and ovary

Front 38

Where are ovules found in the flower?

Back 38

found in the ovary of the flower

Front 39

How might wind pollinated flowers be adapted?

Back 39

Many small, light pollen grains.

Anthers hang outside the flowers.

Small petals.

Large feathery stigmas which hang outside the petals

Front 40

How might insect pollinated flowers be adapted?

Back 40

Large, bright petals, scent and nectar to attract insects.

Anthers and stigmas inside the flower (insects brush against them when collecting nectar.)

Few large and sticky pollen grains to attach to insects.

Front 41

What happens during fertilisation, after the pollen grains attach to the stigma?

Back 41

A pollen tube grows through the carpel's style into the ovule.

The two male nuclei from the pollen grain migrate into the ovule.

They fertilise the egg nucleus and the endosperm nuclei.

The resulting zygote develops into an embryo.

The endosperm forms a fruit store.

The endosperm and female tissues of the ovule give rise to a seed.

The ovary then grows into a fruit, which surrounds the seed.