Download Plants and photosynthesis

9C
Quick Quiz
On your answer sheet, write in or circle the correct letter for each question.
9Ca
9
C
1 Where does
photosynthesis
occur in a
rose bush?
2 Gases get into and out of a leaf by:
S
R
Q
A in all the parts
P
A diffusion.
B absorption.
C conduction.
D convection.
3 Look at this list of substances.
glucose
fat
cellulose
protein
B in parts R and S only
Which of these substances can plants make?
C in part R only
A glucose and cellulose only
D in part Q only
B glucose, cellulose and fat
C glucose, cellulose and protein
2 Plants often turn some of the food they
make into another substance for storage.
The name of this substance is:
A glucose.
B starch.
C fibre.
D pasta.
D all of them
4 Plants need cellulose to:
A store energy.
B repair damaged cells.
C make cell walls.
D make cell surface membranes.
3 Which of these shows the correct word
equation for photosynthesis?
A glucose + carbon dioxide → water +
oxygen (+ energy)
B glucose (+ energy) → oxygen + glycerol
C water + carbon dioxide (+ energy)
→ glucose + oxygen
D chlorophyll + carbon dioxide → water
+ glycogen
4 Aerobic respiration is a process which:
9Cc
1 The picture shows a
cell from a root.
What is it called?
A xylem cell
B root cortex cell
C root palisade cell
D root hair cell
2 If plants do not get enough water they
start to:
A stores chemical energy in food.
B makes food for plants living under
water.
A shrink.
C does not happen in plants but only in
humans when they exercise hard.
C grow bigger roots.
B grow towards the light.
D wilt.
D releases energy from food.
3 One important type of mineral salt is:
9Cb
1 Leaves are often wide so that they can:
A nitrate.
B sodium chloride.
C clay.
D loam.
4 Water is carried up a plant in xylem tubes.
What else do xylem tubes carry?
A absorb as much sunlight as possible.
B catch as much rain as possible.
C provide shelter for animals living
under them.
A glucose
B fibre
C mineral salts
D pollen
D float to the ground when they drop
in autumn.
Page 1 of 2
Exploring Science for QCA
Copymaster File 9
92
© Pearson Education Limited 2002
9C
Quick Quiz (continued)
9Cd
1 The atmosphere is about:
A 80% oxygen and 20% nitrogen.
B 80% nitrogen and 20% oxygen.
C 80% carbon dioxide and 20% oxygen.
D 80% oxygen and 20% carbon dioxide.
9
C
2 Look at these chemical processes.
photosynthesis
respiration
burning fuels
Which of these processes add carbon
dioxide to the air?
A respiration and burning
B respiration only
C photosynthesis and respiration
D burning only
3 Plants are important in keeping the
atmosphere in balance because:
A they use up oxygen.
B they use up carbon dioxide.
C they provide food for animals and
humans.
D they use water.
4 Which of these would not be a
disadvantage of cutting down forests?
A Logging companies could make more
profits.
B There would be fewer trees to keep the
atmosphere in balance.
C Some species might become extinct.
D Floods might wash away the soil.
Page 2 of 2
Exploring Science for QCA
Copymaster File 9
93
© Pearson Education Limited 2002
Target Sheet
9C
Name
Topic
9Ca
9
C
9Cb
9Cc
9Cd
Class
1
Targets
Know where photosynthesis occurs.
2
Know how plants store the food they
make.
3
Know the word equation for
photosynthesis.
4
Know what aerobic respiration is and
where it occurs
1
Know how leaves are adapted to the
job they do.
2
Know how gases get into and out of
leaves.
3
Know what the products of
photosynthesis are used to make.
4
Know why plants need the different
substances they make from glucose.
1
Know how roots are adapted to the
job they do.
2
Know why plants need water.
3
Know some of the mineral salts
needed by plants.
4
Know how substances are transported
around a plant.
1
Know which gases form the
atmosphere.
2
Know which processes add carbon
dioxide to the atmosphere.
3
Know why plants are important in
keeping the atmosphere in balance.
4
Understand some consequences of
clearing forests.
Exploring Science for QCA
Copymaster File 9
Before the unit
94
I have learned this
I have revised this
© Pearson Education Limited 2002
Word Sheets
9C
Word sheets that include new words from the ‘Focus on:’ pages are available on the
Exploring Science website.
9Ca – A light reaction/Plants respire too
Word
Pronunciation
Meaning
aerobic respiration
air-O-bick
res-per-ay-shun
Chemical reaction that releases energy from glucose. It uses up oxygen and produces
carbon dioxide and water.
biomass
chlorophyll
The mass of material (except water) that makes up an organism.
klor-O-fill
glucose
photosynthesis
Green substance found inside chloroplasts. It absorbs light.
Type of sugar made during photosynthesis.
foto-sinth-e-sis
Chemical reaction that plants use to make their own food. It needs light to work.
Carbon dioxide and water are the reactants and glucose and oxygen are the products.
raw material
Something used up in a chemical reaction. Also called a reactant.
reactant
Something used up in a chemical reaction. Also called a raw material.
phloem tube
flow-em
product
Tube made from chains of living phloem cells. Carries glucose and other soluble
substances up and down the plant.
Something made in a chemical reaction.
starch
Insoluble carbohydrate made from glucose and used as a storage material in plants.
word equation
Simple way of showing what happens in a chemical reaction.
9Cb – Leafy adaptations/Sugary food
Word
Pronunciation
adapted
amino acids
Meaning
When something has a particular shape to help it do a function (job). A root hair cell
has a shape that helps it absorb water and is said to be ‘adapted to its function’.
am-mee-no ass-ids
biomass
The building blocks of proteins.
The mass of material (except water) that makes up an organism.
cellulose
A substance used to make cell walls.
chlorophyll
klor-O-fill
Green substance found inside chloroplasts. It absorbs light.
chloroplast
klor-O-plast
Green disc containing chlorophyll. Found in plant cells. Where glucose is made
by photosynthesis.
diffusion
dif-few-shun
The random movement of particles from where there are a lot of them to where there
are fewer of them.
fat
Substance needed by living things to make cell membranes. Our bodies also use fats as
a store of energy and to keep warm.
function
Something’s job.
guard cells
Cells which open and close the stomata.
mineral salt
nitrate
Chemical found in soil that plants need to grow healthily.
night-rate
oil
palisade cells
Mineral salt that plants need to make proteins.
Liquid fat, often found in nuts and seeds.
pall-iss-aid
Cells found in leaves, containing many chloroplasts.
protein
A substance made from amino acids. Proteins are needed for growth and repair.
starch
Insoluble carbohydrate made from glucose and used as a storage material in plants.
stoma
stO-ma
Singular of stomata.
stomata
stom-mart-a
Small holes on the underside of leaves which let gases into and out of the leaf.
Page 1 of 2
Exploring Science for QCA
Copymaster File 9
95
© Pearson Education Limited 2002
9
C
9C
Word Sheets (continued)
9Cc – The root of the matter
Word
9
C
Pronunciation
Meaning
absorb
Soak up.
function
Something’s job.
mineral salt
Chemical found in soil that plants need for healthy growth.
nitrate
night-rate
Mineral salt that plants need to make proteins.
phloem tube
flow-em
Tube made from chains of living phloem cells. Carries glucose and other soluble
substances up and down the plant.
root hair cell
Cell found in roots. The root hair has a large surface area to help the cell absorb water
quickly.
wilting
When a plant does not have enough water and droops.
xylem tubes
zy-lem
Tube made from chains of dead, hollow xylem cells. Carries water and dissolved
mineral salts up a plant.
9Cd – A changing atmosphere
Word
Pronunciation
Meaning
global warming
The process of the Earth’s atmosphere warming up. It is partly caused by an increase in
carbon dioxide in the air.
methane
The gas that is ‘natural gas’. Also formed in large amounts in the digestive systems of
cows. Methane absorbs heat and so helps global warming.
Page 2 of 2
Exploring Science for QCA
Copymaster File 9
96
© Pearson Education Limited 2002
End of Unit Test
9C
Name
Class
1 The drawing shows a bean seedling.
LIGHT
a Why is the plant not growing straight up?
9
C
[1 mark]
b The roots have a number of functions.
Tick the two functions of roots.
X
Absorb carbon dioxide from the air.
Absorb glucose from soil.
Make food for the plant.
Absorb water and mineral salts from the soil.
Hold the plant in the soil.
Make seeds for new plants to grow.
[1 mark]
c What are the names of the parts marked ‘X’ in the drawing?
[1 mark]
d Explain how these parts help the root to work efficiently.
[1 mark]
2 Here is a diagram of a palisade cell.
a Where, in a leaf, would you expect to
find palisade cells?
[1 mark]
b What is the name of the part where photosynthesis occurs?
[1 mark]
c What substance does this part contain?
[1 mark]
Page 1 of 3
Exploring Science for QCA
Copymaster File 9
97
© Pearson Education Limited 2002
9C
End of Unit Test (continued)
3 Complete the word equation for photosynthesis:
+ water (+ energy) → glucose +
.
[2 marks]
9
C
4 The drawing shows Marimo weed.
This organism forms into a ball which
fills with a gas during the day and
floats in the water.
a What gas produced by the plant fills
the weed balls?
[1 mark]
b On some days the weed balls float higher in the water. On other days they are
lower in the water. What makes the balls float?
[1 mark]
c Explain why the weed balls float higher on a sunny day.
[2 marks]
5 This experiment was set up.
Elodea pondweed
Tube A kept
in darkness.
water containing hydrogencarbonate indicator
Tube B kept
in the light.
Hydrogencarbonate indicator is red in tap water. It becomes purple if the water
loses carbon dioxide. It becomes yellow if the water gains more carbon dioxide.
a What colour would you expect the indicator to be in Tube A after two days?
[1 mark]
b Explain your answer to part a.
[2 marks]
Page 2 of 3
Exploring Science for QCA
Copymaster File 9
98
© Pearson Education Limited 2002
9C
End of Unit Test (continued)
Amount of starch
contained in leaves
6 Glucose can be turned
into starch in the leaves
and stored. When it is
needed, the starch is
turned back into
glucose. An experiment
was done to see how
the amount of starch in
some leaves changed
during a week. The
results are shown in the
graph.
9
C
0 noon 1 noon 2 noon 3 noon 4 noon 5 noon 6 noon 7
Day
a Explain why the amount of starch in the leaves increases and then decreases,
every 24 hours.
[1 mark]
b Glucose can also be used to make proteins. Which substance is also needed to
make proteins? Tick the correct box.
potassium salts
phosphates
calcium salts
nitrates
[1 mark]
c Apart from starch and proteins, name one other substance that a plant can make
from glucose.
[1 mark]
7 a What is the name of the process that releases energy from food?
[1 mark]
b Where does this process happen in plants and other living organisms?
[1 mark]
c In plants, at which times of day does this process happen?
[1 mark]
d Complete the word equation for this process.
+ oxygen →
+ water (+ energy)
[2 marks]
Page 3 of 3
Exploring Science for QCA
Copymaster File 9
99
© Pearson Education Limited 2002
Summary Sheets
9C
Plants and photosynthesis
Photosynthesis
water + carbon dioxide (+ light energy)
glucose + oxygen









9
C














This is a chemical reaction and so can be written as a word equation:
reactants
(light is not a substance
and so is not a reactant)
products
Light energy and chlorophyll are needed for photosynthesis to happen. The light
energy is changed into chemical energy which is stored in the glucose that is made.
Getting the water
Water is taken out of the soil by
the roots. Roots are branched and
spread out to help them absorb
water from a large volume of soil.
They also have root hair cells
which are adapted to their
function – they have a large
surface area to help them absorb
water quickly. The water flows up
xylem tubes (made of hollow
cells) to the leaf.
xylem tube
root
hair
soil
water and minerals
Many root hair cells
grouped together form
root hair tissue.
Water is also needed because mineral salts are dissolved in it, which are needed to
keep plants healthy. Water also stops plants wilting and can keep their leaves cool.
Getting the carbon dioxide
Air, containing carbon dioxide,
diffuses into leaves through
small holes called stomata.
Leaves are thin so that the
carbon dioxide does not need
to go very far before reaching
the cells that need it.
Photosynthesis can often be
speeded up by increasing the
amount of carbon dioxide
around a plant.
cuticle
upper epidermis
chloroplast
palisade cell
xylem tubes carry water
phloem tubes carry food
vein
lower epidermis
spongy cells
stoma
guard cell
cuticle
Page 1 of 2
Exploring Science for QCA
Copymaster File 9
100
© Pearson Education Limited 2002
9C
Summary Sheets (continued)
Getting the light
Many leaves are wide so that they have a big surface area to trap as much sunlight as
possible. Most photosynthesis happens in the palisade cells which are found near the
upper surface of leaves. Palisade cells are packed with chloroplasts. Chloroplasts
contain chlorophyll which absorbs light energy. Photosynthesis can often be speeded
up by increasing the amount of light.
9
C
Respiration
Plant cells release the energy stored in glucose using aerobic respiration (another
chemical reaction):
glucose + oxygen
carbon dioxide + water (+ energy)
All living cells need energy and so all living cells respire. Respiration happens all the
time but photosynthesis can only happen when there is light.
Uses of glucose
Glucose is a type of sugar. It is used for three things:
● respiration
● making other substances that act as stores of energy (eg starch)
● making new materials for growth.
Glucose is turned into cellulose (for cell walls), fats and proteins. To make proteins,
mineral salts called nitrates are needed.
New substances made by a plant are carried around the plant in phloem tubes. New
substances help to build up a plant’s biomass (the mass of all the materials in the
plant except water).
Page 2 of 2
Exploring Science for QCA
Copymaster File 9
101
© Pearson Education Limited 2002
Mark schemes
9C
Quick Quiz
Matching End of Unit Test marks to NC levels
Question
Answers
Marks
Level
Marks
available
Cumulative
total
Suggested
threshold for
achieving level
Topic
1
2
3
4
9Ca
C
B
C
D
4
9Cb
A
A
D
C
4
3
2
2
2
9Cc
D
D
A
C
4
4
1
3
3
9Cd
B
A
B
A
4
5
5
8
6
6
11
19
14
7
4
23
21
8
1
24
Insufficient marks to
justify level
EP
1
25
Insufficient marks to
justify level
9
C
End of Unit Test marks
Question
Level
Answers
Mark scheme
1
3
a Plant shoots grow towards light.
1 mark
3
b Absorb water and mineral salts from the soil; hold
the plant in the soil.
c root hairs/root hair cells
d They have a large surface area to help absorb
water.
1 mark –
4
7
mark for each.
1 mark
1 mark
2
6
6
7
a upper part of leaves
b chloroplast
c chlorophyll
1 mark
1 mark
1 mark
3
5
carbon dioxide; oxygen
2 marks
4
5
6
6
a oxygen
b more gas in the balls
c Higher temperature/more light increases the
speed of photosynthesis; so more oxygen is
produced.
1 mark
1 mark
2 marks – 1 mark for each point. Accept higher temperature
causes the gases in the balls to expand.
5
5
6
a yellow
b The weed is respiring which gives out
carbon dioxide; it is not photosynthesising which
would use up carbon dioxide.
1 mark
2 marks – 1 mark for each point
6
7
2 marks – 1 mark for each point
EP
8
a Starch is made during daylight from glucose
by photosynthesis; it is used up at night by respiration.
b nitrates
c fats/cellulose/sucrose
1 mark
1 mark
5
6
6
6
a respiration
b in all cells
c at all times
d glucose, carbon dioxide
1 mark
1 mark
1 mark
2 marks – 1 mark for each substance
7
Exploring Science for QCA
Teacher’s Guide 9
© Pearson Education Limited 2003
53
9Ca/1
Measuring
photosynthesis 1
Name
Class
You are going to try to find out how light affects the amount of photosynthesis.
Prediction
9
C
a
Read the instructions and then complete the sentence below.
I think the gas will collect fastest when the light is
(further away from the beaker/closest to the beaker).
P
Apparatus
●
●
●
Elodea pondweed
Large beaker
Pondwater
●
●
●
Glass funnel
Marker pen
Ruler
●
●
●
Lamp
Narrow bung
Stopclock
Method
1 Measure 1 cm from the end of the funnel and make a mark.
2 Set up the apparatus but do not put the bung in yet. Make sure the water
level is above the top of the funnel.
3 Place the lamp 10 cm away
from the beaker. Wait for two
minutes and then put in the
bung and start the stopclock.
bung
mark, 1 cm from the end
bubble of gas
4 Stop the stopclock when the gas
bubbles have filled the end of the
funnel down to your mark. Write
down how long this took in seconds.
water
funnel
5 Repeat steps 2 and 3 at various
distances between the lamp and
the beaker. Write down which distances you choose.
pondweed
Recording your results
Fill in this table with your results.
Distance between lamp and beaker (cm)
Time it took for end of funnel to fill with gas (s)
Page 1 of 2
Exploring Science for QCA
Copymaster File 9
102
© Pearson Education Limited 2002
9Ca/1
Measuring photosynthesis 1
(continued)
Considering your results/conclusions
What gas collected in the
syringe?
What was the relationship
between the distance of
the lamp (to the beaker)
and the amount of time
it took to fill the end of
the funnel?
The closer the lamp was to
the beaker,
Time it took for end of funnel to fill with gas (s)
Draw a line graph to show
your results.
9
C
a
Distance between lamp and beaker (cm)
Evaluation
There is a problem with this experiment. The lamp will give out heat which may heat
up the water and give you a false result.
How do you think having hotter water affects the results?
Why do you think this?
Try to think of a way of stopping the lamp heating up the water.
S
planning, observing, considering, evaluating
Exploring Science for QCA
Copymaster File 9
103
Page 2 of 2
© Pearson Education Limited 2002
9Ca/2
Measuring
photosynthesis 2
You need to try to find out how different variables (or factors) affect the amount of
photosynthesis in some pondweed.
Planning
1 Variables: what could you change that might affect how fast photosynthesis occurs?
●
9
C
a
●
●
The amount of light (light intensity) can be altered using a lamp.
Extra carbon dioxide can be put into the water by adding sodium
hydrogencarbonate.
Water baths can be set to different temperatures.
2 Choose one or two variables to test.
● How will you change them? How many times will you change them?
● What will you measure? Can you find a way of measuring how much gas is
produced by the pondweed?
● How long will you run the experiment for?
● What apparatus will you need and how will you set it up?
3 Fair test: you should only change one variable at a time. Write down all the
variables you will keep the same.
4 Prediction: write down what you think will happen. Use your scientific knowledge
to explain why you think this will happen. You will need to know about
photosynthesis.
5 How will you make this a safe investigation?
6 Show your plan to your teacher before you begin.
S
planning
Exploring Science for QCA
Copymaster File 9
104
© Pearson Education Limited 2002
9Ca/3
Leaves and
photosynthesis
Is light needed for photosynthesis? – Instruction Sheet
P
Apparatus
●
●
●
●
●
●
Leaves for testing – one that has been in the light and one that has been in
the dark
● Pipette
● Scissors
Iodine solution
● Ethanol
● Tripod
Bunsen burner
● Gauze
● Boiling tube
Large beaker
● Test tube holder
● Eye protection
Heatproof mat
● Petri dish
Forceps
Method
1 Take two leaves, one which has been in the light and one which has been in
the dark. Cut the end off the one that has been in the dark, so you can
remember which is which.
beaker
2 Place both leaves in a beaker of boiling
water for one minute.
water
leaves
gauze
3 Turn off the Bunsen burner. Wait until you
are told to continue.
4 Half fill a boiling tube with ethanol. Place
the two leaves in it using forceps. Place
the test tube in the beaker of hot water
and leave it for five minutes.
5 Take the leaves out of the test tube and
wash them with tap water.
tripod
Bunsen burner
test tube
of ethanol
hot water
leaves
beaker
gauze
tripod
6 Place the leaves on a Petri dish and add 5
drops of iodine solution to each leaf. If a
blue-black colour appears, then there is
starch in the leaf. Starch is only made in a
leaf when photosynthesis has happened.
Exploring Science for QCA
Copymaster File 9
105
• Ethanol catches fire very
easily. Do not put it
anywhere near a lighted
Bunsen burner.
• Take care with the Bunsen
burner, the beaker and the
water. They get very hot.
• Take care when boiling
water. Wear eye protection.
© Pearson Education Limited 2002
9
C
a
9Ca/4
Leaves for
photosynthesis 1
Name
Class
Is light needed for photosynthesis?
9
C
a
You will need the instruction sheet 9Ca/3 Leaves and photosynthesis.
Prediction
Tick the box next to the sentence that says what you think will happen.
Both leaves will go blue-black because both leaves have been photosynthesising.
Only the leaf that had been in the dark will go blue-black because photosynthesis
happens in the dark.
Only the leaf that had been in the light will go blue-black because photosynthesis
happens in the light.
Recording your results
Describe in your own words what happened.
Considering your results/conclusion
What substance goes blue-black when iodine is added to it?
What process makes this substance?
What colour did the leaf that had been in the dark go when iodine solution was
added?
What colour did the leaf that had been in the light go when iodine solution was
added?
Which of these sentences is true? Tick the right one.
Starch is made in leaves
in the light.
Starch is made in leaves
in the dark.
Starch is made in leaves
happens in the light.
Starch is made in leaves
happens in the dark.
S
that are photosynthesising. Photosynthesis only happens
that are photosynthesising. Photosynthesis only happens
that are not photosynthesising. Photosynthesis only
that are not photosynthesising. Photosynthesis only
knowledge, observing, considering
Exploring Science for QCA
Copymaster File 9
106
© Pearson Education Limited 2002
9Ca/5
Leaves for
photosynthesis 2
Is light needed for photosynthesis? Is chlorophyll needed for
photosynthesis?
You will need the instruction sheet 9Ca/3 Leaves and photosynthesis.
Prediction
1 Which leaf do you think will have starch in it? Explain why you think this.
Recording your results
2 Write down what happened. What colours did each leaf go when iodine solution
was added? Did all of the parts of the leaves change colour?
Considering your results/conclusions
3 If you add iodine solution and a blue-black colour appears, what substance
is present?
4 What process produces this substance?
5 Which parts of which leaf do you think had been photosynthesising?
Why do you think this?
6 Write down whether you think light is needed for photosynthesis and why you
think this.
7 If you have used a variegated leaf write down whether you think chlorophyll is
needed for photosynthesis and why you think this.
S
knowledge, observing, considering
Exploring Science for QCA
Copymaster File 9
107
© Pearson Education Limited 2002
9
C
a
9Ca/6
?
Respiration and
photosynthesis 1
1 Copy and complete these word equations.
a Photosynthesis:
(+ light energy) →
carbon dioxide +
+ glucose
b Aerobic respiration:
9
C
a
oxygen +
→
+ water (+
Amount of
carbon dioxide
2 Scientists can find out about
photosynthesis by measuring the
concentration of different gases
near plants. This graph shows the
concentration of carbon dioxide in
the air around an oak tree during a
day in May.
)
a Which process in a plant uses up
carbon dioxide?
0 2 4 6 8 10 12 14 16 18 20 22 24
noon
Time of day (hours)
b When do you think carbon dioxide
was being used up by the tree?
c At which times of the day do you think that the light was brightest?
Explain your answer.
d What does this tell you about the process that uses up carbon dioxide?
3 It is known that photosynthesis
gets faster if there is more light.
It is also known that
photosynthesis gets faster if
there is more carbon dioxide.
This experiment was set up to
see if this was also true for
plants that grow under water.
bubbles of gas
pondweed
a What gas did the bubbles contain?
Write down whether each of the following changes would make the number
of bubbles go up or down. Explain your reasoning.
b The light bulb was moved further away.
c Why do you think this?
d Extra carbon dioxide was dissolved in the water.
e Why do you think this?
S
knowledge
Exploring Science for QCA
Copymaster File 9
108
© Pearson Education Limited 2002
Respiration and
photosynthesis 2
9Ca/7
Joseph Priestley (1733–1804) did some experiments similar to these to show that air
was changed by plants and animals. Some bell jars are set up with plants inside. After
a week the air from the bell jars is used to see if a candle will burn for more or less
time than in a bell jar of normal air.
A
B
C
D
E
soda lime
This bell jar was placed
under a lamp for a week.
?
This bell jar was placed
under a lamp for a week.
This bell jar was placed
under a lamp for a week.
This bell jar was placed in
the dark for a week.
This bell jar was placed
under a lamp for a week.
1 For each bell jar (A–E) write down whether a lighted candle would burn for
more or less time than in a bell jar of normal air. Explain your reasoning in
each case.
2 The air inside one of the bell jars allows a candle to burn for longer than the
others. Which one? Explain your reasoning.
3 A leaf was taken from each plant, boiled with ethanol and tested with
iodine solution.
a What is being tested for?
Scientists can find out about photosynthesis
by measuring the concentration of different
gases near plants. This graph shows the
concentration of carbon dioxide in the air
around an oak tree during a day in May.
Amount of
carbon dioxide
b Describe what you would see when iodine solution was added to each
leaf. In each case explain why you think this would happen.
0 2 4 6 8 10 12 14 16 18 20 22 24
noon
Time of day (hours)
?
4 a Which process in a plant uses up carbon dioxide?
b Write a word equation for this process.
c Explain why the concentration of carbon dioxide varies as shown in the
graph.
d Make a copy of the graph, and add another line to show how you think
the concentration of oxygen in the air around the tree would change over
the same time. Explain the shape of your line.
S
knowledge
Exploring Science for QCA
Copymaster File 9
109
© Pearson Education Limited 2002
9
C
a
9Ca/8
Biological symbol
equations
Every chemical can be represented by a chemical formula which uses symbols and
numbers. The symbols show the different atoms and the numbers show how many
atoms there are. For example, water has two hydrogen atoms and one oxygen atom
and so its formula is H2O. These formulae can be used to write symbol equations.
The reaction between hydrogen and oxygen to make water can be shown like this:
H2 + O2 → H2O
9
C
a
We need to have these as H2 and O2
because they exist as molecules of two
atoms joined to each other.
However, the symbol equation needs to have the same number of each type of atom
on each side. At the moment there is only one oxygen atom on the right but two on
the left. We add numbers at the start of each chemical formula to balance the number
of atoms on each side of the equation.
2H2 + O2 → 2H2O
This is now a balanced symbol equation which shows that two molecules of
hydrogen react with one molecule of oxygen to form two molecules of water.
?
1 a Write down the formula for carbon dioxide.
b How many carbon atoms are there in a molecule of carbon dioxide?
c How many oxygen atoms are there?
d How many oxygen atoms are there in a molecule of water?
2 a Write down the word equation for photosynthesis (leave out the
‘energy’ bit).
b The formula for glucose is C6H12O6. Write down a balanced symbol
equation for photosynthesis. (Hint: Don’t put a number in front of the
glucose formula.)
3 The formula for starch is (C6H12O6)n, where ‘n’ means a large number. The
formula in the brackets tells you what sort of molecules there are a large
number of.
a What molecules are there a large number of in starch?
b Write down a balanced symbol equation for how starch is made.
4 Starch is usually broken down again into small molecules which are used to
release energy in cells.
a What process releases energy in cells?
b Write down its word equation (leave out the ‘energy’ bit).
c Write down its balanced symbol equation.
S
literacy, knowledge
Exploring Science for QCA
Copymaster File 9
110
© Pearson Education Limited 2002
Gas exchange in an
oak tree
9Ca/9
30
25
20
9
C
a
15
10
5
0
18:00
17:00
16:00
15:00
14:00
13:00
12:00
11:00
10:00
09:00
08:00
07:00
06:00
05:00
04:00
03:00
02:00
–10
01:00
–5
00:00
Amount of carbon dioxide diffusing
into the oak tree (cm3/m2/min)
An experiment was done to measure the amount of carbon dioxide diffusing into an
oak tree on a partially cloudy day in May. The experiment was done over 18 hours
and the results are shown in the graph below.
Time of day
?
1 The units for the amount of carbon dioxide that diffuses into the leaves is
given as cm3/m2/min – that is cm3 of carbon dioxide per m2 of leaf area per
minute. How much carbon dioxide was diffusing into the plant at:
a 14:00 hrs
b 09:00 hrs?
2 a The line is below 0 cm3/m2/min for the first part of the day. Explain what
this tells you.
b What process causes this to happen?
c What time do you think dawn was? Explain your answer.
3 a The time at which there is no overall diffusion of carbon dioxide into or
out of the tree is called the compensation point. At what time did the
compensation point occur?
4 For each part of this question, explain your answer. How would the time of
the compensation point change if:
a the skies were clear
b it was partially cloudy but colder
c it was the middle of winter? (Be careful!)
5 a What was the maximum rate of diffusion of carbon dioxide into the leaf?
b The whole tree had leaves with a total surface area of 50 m2. How much
carbon dioxide would have diffused into the tree in 12 hours if the diffusion
stayed at its maximum rate? Show your working. Give your answer in cm3.
c There are 1000 cm3 in 1 litre. Write down the answer to part b in litres.
d One litre of carbon dioxide has a mass of 1.8 g. Write down your answer to
part c in kilograms of carbon dioxide.
6 Sketch a graph to show what you would expect to find if the amount of
diffusion of oxygen into the leaves had been measured instead.
S
knowledge, considering, numeracy
Exploring Science for QCA
Copymaster File 9
111
© Pearson Education Limited 2002
Leafy matters 1
9Cb/1
Name
?
Class
1 This diagram shows part of a leaf.
Fill in the labels on the diagram using words from the box.
air space
cuticle
guard cell
palisade cell
9
C
b
spongy cell
stoma
2 Fill in the gaps in these sentences using words from the box. You may need
each word once, more than once, or not at all.
carbon dioxide
light
losing
cells
night
chloroplasts
oxygen
small
heat
holes
stomata
much water. The palisade cells have lots of
absorb
a
waterproof
layer that stops the leaf
The cuticle is a
large
too
to
energy to make photosynthesis happen. Leaves have
surface area so they can absorb a lot of
Cells in the leaf need to absorb
into the leaf through
Guard
energy.
from the air. Air gets
in the bottom surface called
can close the stomata at
.
to stop the leaf
water.
3 Some of the glucose made in photosynthesis is used to make new materials for
the plant. Match up the materials with their uses.
S
Amino acids
A store of energy in some seeds and special organs like
potatoes.
Cellulose
Energy stores found in some nuts.
Fats
Used to make proteins.
Oils
Used to make cell walls.
Starch
Used in cell surface membranes.
knowledge, literacy
Exploring Science for QCA
Copymaster File 9
112
© Pearson Education Limited 2002
Leafy matters 2
9Cb/2
?
1. The drawing shows a slice through a leaf.
D
G
C
9
C
b
A
P
E
B
F
Q
a What are the names of the parts labelled A–G? Use these words to help you:
air space, chloroplast, cuticle, guard cell, palisade cell, spongy cell, stoma.
b Water vapour is lost from leaves. Arrow P shows water vapour leaving the
cells. What is the name of this process?
c Arrow Q shows the water vapour escaping from the leaf. What is the name
of this process?
2 a In which cells does most photosynthesis happen?
b How are these cells adapted to carry out photosynthesis?
c Where are these cells located in a leaf?
d Why do you think they are in this position?
3 Suggest a reason for each of these observations:
a Leaves have a large surface area.
b Leaves are thin.
c Leaves often grow in such a way that they do not shade one another.
d Stomata are shut at night.
4 a Name three types of substance that a plant makes using glucose.
b What is each type of substance used for?
S
literacy, knowledge
Exploring Science for QCA
Copymaster File 9
113
© Pearson Education Limited 2002
9Cb/3
Discovering
photosynthesis
In the 17th century it was believed that everything was made up of four elements –
earth, fire, water and air. Plants were believed to be made from fire and earth. JeanBaptiste van Helmont (1579–1644) did an experiment to show that this was wrong.
9
C
b
small willow tree
(mass = 2.27 kg)
willow tree
(mass = 76.74 kg)
5 years
watered regularly
mass of pot + dry soil
= 90.72 kg
mass of pot + dry soil
= 90.66 kg
Van Helmont said that his experiment showed that a plant could not be made from
earth because the mass of the soil decreased only a little bit but the mass of the willow
tree increased a lot. He said that the extra mass of the tree must be made from water.
In 1771, Joseph Priestley did an experiment which showed that plants produced a gas in
which a candle would burn. He called this ‘dephlogisticated air’ (dee-floj-jiss-tick-ay-ted).
one week later
→
Priestley said that after a while the candle had
produced so much ‘fixed air’ that it went out.
The candle could now burn again. Priestley said
this was because the plant had changed the ‘fixed
air’ into ‘dephlogisticated’ air during the week
In 1754, Charles Bonnet had shown that bubbles were produced by leaves placed
underwater. He said that this was due to dissolved air in the water sticking to the
leaves. However, in 1779, Jan Ingenhousz showed that leaves placed underwater
produced bubbles of ‘dephlogisticated air’ but only when the Sun was shining. He also
showed that only the green parts of plants would do this.
Later in 1782, Jean Senebier showed that ‘fixed air’ contained carbon dioxide and that it
was used up by the plant. During this time the idea that mass was conserved in reactions
was put forward. In 1804, Theodore de Saussure found that the mass of carbon dioxide
used up by a plant was not enough to account for the increase in mass of the plant.
Since the only other thing needed to keep the plant alive was water, he suggested that
both carbon dioxide and water were changed by the plant into new material.
Page 1 of 2
Exploring Science for QCA
Copymaster File 9
114
© Pearson Education Limited 2002
9Cb/3
?
Discovering photosynthesis
(continued)
1 a Write down the word equation for photosynthesis.
b Which substances are the reactants?
c Which scientist showed that light was needed for photosynthesis to happen?
d What observation led him to develop this theory?
2 a What is the modern word for the gas produced by the candle to make
‘fixed air’?
b What is the modern word for the gas produced by the plant to make
‘dephlogisticated air’?
3 a Suggest how Ingenhousz may have collected a sample of ‘dephlogisticated
air’.
b How do you think he showed that this was ‘dephlogisticated’ and not
‘fixed’ air?
4 a Do you think van Helmont was successful in what he set out to prove?
Explain your answer.
b Explain why van Helmont’s conclusion was only half right.
c Van Helmont’s tree had a mass of 76.74 kg after five years. Why do you
think that the total mass of material produced by the plant was actually
greater than this?
S
literacy, knowledge
Page 2 of 2
Exploring Science for QCA
Copymaster File 9
115
© Pearson Education Limited 2002
9
C
b
9Cb/4
Transpiration
The loss of water by a plant is called transpiration. There are two processes involved
in this. First, there is evaporation of water from the surfaces of the cells into the air
spaces in a leaf. Second, the water vapour diffuses out of the leaf.
An experiment was set up to investigate transpiration. The same amount of soil was
put into two identical pots and a plant was put into each. One plant had all its leaves
removed. Both were given the same amount of water at the start of the experiment.
9
C
b
clear, colourless
plastic bags
pots containing
damp soil
pot 1
pot 2
The pots were left outside and the masses measured at the end of each day for one week.
Day
Weather
0
1
2
3
4
5
6
7
Cloudy
Sunny
Cloudy
Cloudy
Wet
Sunny &
Sunny
Sunny
windy
Mass of pot 1 (g)
48
41
39
37
37
28
21
18
Mass of pot 2 (g)
41
41
40.5
40.5
40.5
39.5
39
38.5
?
1 Why were the pots covered in plastic bags?
2 What was being lost to make the plants lose mass?
3 What percentage of the original mass of pot 1 was left after one week?
4 Draw a line graph to show both these results. Plot both sets of results on the
same graph.
5 On which day did pot 1 lose most mass?
6 Explain why pot 1 lost more mass than pot 2.
7 Suggest an experiment you could do to find out whether there are more
stomata on the lower surface of a leaf than the upper surface. (Hint: Vaseline
will block stomata; or cobalt chloride paper could be used.)
8 a What general conclusion can you make about the amount of mass lost and
the weather?
b Explain how the weather affects the loss of water by transpiration. Use the
words ‘evaporation’ and ‘diffusion’ in your answer.
9 Look at the leaves on the plant in pot 1. They are arranged so that they do
not overlap each other. This arrangement is called a leaf mosaic. Suggest
what the advantage of this arrangement is.
S
knowledge, presenting, considering
Exploring Science for QCA
Copymaster File 9
116
© Pearson Education Limited 2002
9Cc/1
Adaptations for
photosynthesis
Name
Class
The organs of plants are shaped so that they can carry out their jobs well. They are
said to be adapted to their jobs (or functions).
Water is needed to fill up the cells and help a plant stand up straight. If it does not get
enough water, it wilts. Water is also needed for photosynthesis. The water is taken in
by the roots which are spread through the soil. The many branches of roots also mean
that they hold the plant firmly in the ground. The stem helps to support the leaves
and contains many hollow tubes to carry the water to the leaves. Leaves have small
holes called stomata and gases move in and out of the leaf through these (e.g. carbon
dioxide). Light is also needed for photosynthesis and so most leaves have a large
surface area to collect lots of light.
1 Name two uses of water in a plant.
a
b
2 Name two jobs that roots do.
a
b
3 Name two jobs that stems do.
a
b
4 List the three plant organs named in the passage.
a
b
c
5 In the passage, underline the phrases which are about how an organ
is adapted.
6 In the passage, circle the names of the chemical substances needed
for photosynthesis.
7 Plants use water for photosynthesis. They also lose quite a lot of it.
a Where do you think this water loss happens?
b Why do you think this?
S
literacy, knowledge
Exploring Science for QCA
Copymaster File 9
117
© Pearson Education Limited 2002
9
C
c
9Cc/2
?
Plants and water
1 Water and mineral salts
are taken in through a
plant’s roots. The drawing
shows part of a root.
a What is a cell like the
one labelled ‘X’ called?
9
C
c
b What is its function?
c How is it adapted to
its function?
xylem tube
X
d What is the function of xylem tubes?
2 Which of these processes happens in roots?
photosynthesis
combustion
respiration
neutralisation
3 Explain why the roots of plants usually look white, rather than green.
4 Phloem tubes carry sugar and other substances around plants. Explain why
roots have phloem tubes as well as xylem tubes.
5 Sam kept a plant in a pot in her bedroom. She watered the plant every day,
but it died. Suggest why the plant might have died.
6 Dipesh’s garden has some plants growing in flower beds, and some plants
growing in pots.
Dipesh’s family went away for two weeks in the summer, when the weather
was very hot and dry. When they got back they found that the plants in the
containers had died, but the ones in the flower bed were still growing.
Suggest why this might have happened.
S
knowledge
Exploring Science for QCA
Copymaster File 9
118
© Pearson Education Limited 2002
Carnivorous plants
9Cc/3
There are a few species of plant that trap and digest insects. These plants obtain all their
energy through photosynthesis, so they do not need the insects to provide energy. Many
species of carnivorous plants grow in habitats where the soil does not contain many of
the nutrients they need, and they use the insects they trap to provide nutrients.
Sundews are carnivorous plants that grow in bogs where nitrates are in short supply.
Their leaves are covered with little stalks with glands on the end. If an insect lands on
the leaf it is trapped by a sticky liquid produced by the glands. The little stalks then
gradually curl towards the centre of the leaf, and start to release digestive enzymes.
The diagram shows the results of an experiment to find out if sundews need insects to
supply nutrients.
sand
A
Watered with nutrient
solution including nitrates.
?
B
Watered with nutrient
solution including nitrates.
C
Watered with nutrient
solution without nitrates.
D
Watered with nutrient
solution without nitrates.
1 Suggest why the sundew plants were grown in sand.
2 This table shows the results of the experiment. Copy the table, and fill in the
right-hand columns by putting ticks or crosses. One row has been done for you.
Plant
Mass increase (%)
A
100
B
65
C
145
D
50
Nitrates available via roots?
Nitrates available via leaves?
✓
✗
3 Will sundews grow without a supply of nitrates? Explain your reasoning.
4 Can sundews absorb nitrates through their roots? Explain your answer.
5 Do sundews absorb nitrates best through their roots or through their leaves?
Explain your answer.
6 Why do sundew plants need nitrates?
7 Owen wants to keep a sundew plant in his house, but he does not want
insects in his house. Explain why adding plant food to the soil will not help
the plant to grow as well as it should.
8 Describe an experiment that you could carry out to find out if sundew plants
get phosphates mainly through their roots or their leaves.
9 Find out how Venus flytraps and pitcher plants trap insects.
S
considering, research
Exploring Science for QCA
Copymaster File 9
119
© Pearson Education Limited 2002
9
C
c
9Cd/1
Saving the forests
In many places in South America and Asia, large areas of forest are being cut down to
sell the wood, or so that minerals can be extracted, or to clear land for farming.
Environmental organisations are very concerned about this, and try to get
governments and large companies to help keep the forests.
9
C
d
If a campaign to save the forests is to be successful, campaigners first need to find out
why different people want to cut the trees down, and then find ways to help those
people live or earn a living in a different way.
All these people have different ideas or reasons for clearing the forests, or for wanting
to save them.
?
1 For each person, decide if they want to cut down trees or want to stop
people doing it. Explain why they have these opinions.
2 For the people who want to cut down trees, suggest how they could live or
earn their living in a different way that did not involve cutting down trees.
A
Tropical hardwoods like mahogany and teak are
valuable because they are long lasting and look
good when they are made into furniture. Our
logging company employs many people who would
be out of work if we were not allowed to cut down
trees. We try to cut down only the trees we want
and leave the rest of the forest – this is called
selective logging.
B
We live in the forest. We hunt and fish, and gather
fruit and nuts for food and wood for fuel. Our
traditional way of life will be destroyed if the
forests disappear.
C
Tropical rainforests may contain up to 30 million
species of animals and plants. Many of these
plants could be useful as medicines, but if the
forests disappear we might never know! Many
species will become extinct.
D
It is all very well you rich countries saying we must
not cut down our forests, but we have very poor
people here who need the land to farm, and our
economy needs to make money by selling wood,
and we need the land for crops like sugar and
cocoa, or for mining. Many of your own companies
have cleared large areas of forest to convert to
grassland, just so you can have cheap beef!
Page 1 of 2
Exploring Science for QCA
Copymaster File 9
120
© Pearson Education Limited 2002
9Cd/1
Saving the forests (continued)
I have to grow food. I cut down a small area of the
forest and burn the wood, then grow food for me
and my family. After a few years the crops do not
grow as well any more, and I need to clear a new
patch of forest.
E
F
9
C
d
After a patch of forest has been farmed it can take
20 years or more before the trees grow back. There
are more people on the land now, so the land does
not usually get time to recover properly. There are
ways of growing trees in combination with crops
that would help to avoid this problem, but the poor
farmers would have to be taught how to use them.
Selective logging takes only the most valuable
trees, but damages a lot more of the forest. There
are different ways of managing the forest so that
not too much damage is done, but timber can still
be harvested.
G
H
Trees return a lot of water to the air – this
increases local rainfall and makes sure there is
plenty of water for the people living nearby. The
trees also stop rainfall running away too quickly. If
the trees are cut down, there may be more floods
and the soil could also be washed away.
The world needs metals and other minerals that
we mine from the forest areas. I know it causes
damage, but the trees will grow back!
I
J
We can try to use up less fossil fuels, but that
won’t help if there are no trees left! We will still
need lots of trees to use up the carbon dioxide that
people and animals make.
S
knowledge, literacy
Page 2 of 2
Exploring Science for QCA
Copymaster File 9
121
© Pearson Education Limited 2002
Plants and
photosynthesis
9Cd/2
Use the phrases and diagrams below to make a poster showing the important facts
about plants and photosynthesis. Add your own labels and drawings if you need to.
Your poster should include information on:
9
C
d
•
•
•
•
which substances plants use to produce biomass
what source of energy is needed for photosynthesis
what happens in leaves, and how they are adapted to their function
what happens in roots, and how they are adapted to their function.
S
revision
✄
Roots take in water and
mineral salts
from the soil.
Root hair cells have a
large surface area to help
them absorb water.
Carbon dioxide diffuses
into leaves through the
stomata.
Water and mineral salts pass
up through the stem of the plant
in xylem tubes.
Light is needed for photosynthesis.
Leaves have a large surface area.
Palisade cells have a lot of chloroplasts.
carbon dioxide + water (+ light energy) → glucose + oxygen
DO NOT MAKE A DOUBLE SIDED PHOTOCOPY OF THIS WORKSHEET
Exploring Science for QCA
Copymaster File 9
122
Page 1 of 2
© Pearson Education Limited 2002
9Cd/2
Plants and photosynthesis
(continued)
9
C
d
Page 2 of 2
Exploring Science for QCA
Copymaster File 9
123
© Pearson Education Limited 2002
Plants
true/false
revision
Copymaster File 9
124
© Pearson Education Limited 2002
revision
Exploring Science for QCA
S
Copymaster File 9
124
© Pearson Education Limited 2002
12 Plants are important in making carbon dioxide to
keep the atmosphere in balance.
12 Plants are important in making carbon dioxide to
keep the atmosphere in balance.
For each statement, write down whether it is true or
false. If it is false, write out a correct version.
Plants
true/false
1 New material in plants is called biomass.
2 Plants use soil and water to make new biomass, in a
process called respiration.
3 Sound energy is needed for photosynthesis to happen.
4 Photosynthesis produces glucose and carbon dioxide.
5 Photosynthesis happens mainly in the palisade cells
in the roots.
6 Palisade cells are adapted to their function by having
lots of chloroplasts.
7 Plants use glucose to make cellulose, fats, proteins
and starch.
8 Roots take in the water needed by the plant, and
also mineral salts.
9 Roots are adapted to take in water by having a small
surface area.
10 Water travels up the plant in tubes called xylem
tubes.
11 Plants need carbon dioxide to make glucose.
?
9Cd/3
1 New material in plants is called biomass.
2 Plants use soil and water to make new biomass, in a
process called respiration.
3 Sound energy is needed for photosynthesis to happen.
4 Photosynthesis produces glucose and carbon dioxide.
5 Photosynthesis happens mainly in the palisade cells
in the roots.
6 Palisade cells are adapted to their function by having
lots of chloroplasts.
7 Plants use glucose to make cellulose, fats, proteins
and starch.
8 Roots take in the water needed by the plant, and
also mineral salts.
9 Roots are adapted to take in water by having a small
surface area.
10 Water travels up the plant in tubes called xylem
tubes.
11 Plants need carbon dioxide to make glucose.
For each statement, write down whether it is true or
false. If it is false, write out a correct version.
Exploring Science for QCA
S
?
9Cd/3
9
C
d
9Cd/4
Amazon rainforest
This article about deforestation in the Amazon rainforest was published on the New
Scientist website in 2001.
Trees toppled
Amazonia,’ Mary Allegretti, Brazil’s secretary
of co-ordination for the Amazon, told Reuters.
12:30 16 May 01
Deforestation of the Brazilian Amazon during
2000 hit the highest levels since 1995, satellite
images have revealed.
Data from Brazil’s National Institute for
Space Research (INPE) show 0.56 per cent of
the rainforest was cut down in 2000. Over
12 250 square kilometres were logged,
compared with 10 660 in 1999.
‘The beginning of the new millennium
could not have been worse for the Amazon.
The figures are worrying if we look to the
future,’ says the World Wildlife Fund.
The rise was mostly down to increased
logging by small-scale farmers, says INPE. In
response, Brazil’s environment ministry
announced plans to introduce a logging
licensing system, which will allow only
holders of ‘environmental licences’ to cut
down trees.
‘At first we will concentrate our work in the
worst-affected areas, but the demand for
licences on rural properties will apply for all of
?
Put to the vote
Official figures had showed a gradual
reduction in logging since 1995, when 0.8 per
cent of the forest in Brazil was destroyed.
However, a government bill that would
allow Brazilian farmers to legally log larger
areas of the Amazon is due to be put to the
vote on 30 May. Environmentalists are
campaigning against any change to the
logging laws.
Most of the Amazon, which stretches over
an area larger than western Europe, is in
Brazil. The Amazon represents 40 per cent of
the world’s rainforest and is an important sink
for the greenhouse gas, carbon dioxide.
Related story: Amazon rainforest could
suffer huge damage from road building
(19/01/01).
Emma Young
1 How was the information about deforestation obtained?
2 a How much of the Brazilian Amazon rainforest was cut down in 2000?
b Is the amount cut down each year increasing or decreasing?
3 Who is doing most of the logging?
4 a How is the Environment Ministry in Brazil planning to control the logging?
b Will this reduce the area of rainforest cut down each year? Explain
your answer.
5 Why is it important to control logging in the Amazon rainforest?
6 If you lived in Brazil, would you want the government to allow logging or to
try to reduce the amount of logging? Write a letter to the Environment
Ministry to explain your opinion. You may need a copy of Worksheet 9Cd/1
to help you.
S
knowledge, literacy
Exploring Science for QCA
Copymaster File 9
125
© Pearson Education Limited 2002
9
C
d
9Cd/5
Plants kriss-kross
Name
?
Class
Answer the clues below and then use the answers to fill in the grid. There are
no clue numbers so you will need to find a way of getting all the answers to
fit in the grid properly. Use a pencil in case you make a mistake.
9
C
d
A green chemical needed to allow photosynthesis to happen.
A green disc found in palisade cells.
A plant does this if it does not get enough water.
A product of photosynthesis which is a gas.
A product of photosynthesis which is a solid.
A reactant in photosynthesis which is a liquid.
A substance which a plant can make as a store of energy.
An important mineral salt needed to make proteins in plants.
Holes in leaves surrounded by guard cells.
Hollow cell through which water travels.
Photosynthesis turns light energy into this sort of energy.
Plant organ that takes water from the ground.
Plant organ where photosynthesis happens.
Process in which molecules move from an area where there are a lot of them
to an area where there are fewer of them.
The mass of material that makes up a plant.
The source of energy for photosynthesis.
S
literacy, knowledge
Exploring Science for QCA
Copymaster File 9
126
© Pearson Education Limited 2002
Seasonal changes
Scientists and governments are
getting increasingly worried
about rising levels of carbon
dioxide in the atmosphere, and
the possibility that increased
carbon dioxide will lead to the
mean (average) temperature of
the Earth increasing – an effect
known as global warming.
60°N
60°S
Concentration of CO2
9Cd/6
Monitoring stations have been
set up all over the world to
record the concentrations of
different gases in the
Year 1
Year 2
atmosphere. The graph shows
how the concentration of
Seasonal changes in atmospheric CO2.
carbon dioxide in the atmosphere
changed over four years in the
northern and southern hemispheres.
?
9
C
d
Year 3
Year 4
1 Which natural processes produce carbon dioxide?
2 Which natural processes remove carbon dioxide from the air?
3 How are human activities adding to the amount of carbon dioxide in the air?
4 Look carefully at the line showing carbon dioxide concentrations in the
northern hemisphere.
a At which time of year do the high concentrations occur?
b What do you think causes the highs and lows in this line? (Hint: Think
about when most plant growth occurs.)
5 Look at the line for the southern hemisphere. Why are the highs and lows
on this line in different places to the ones for the northern hemisphere?
6 What overall trend do both lines show?
7 Sketch a graph showing how you would expect the concentration of oxygen
in the atmosphere to change over this four-year period. You should include
lines for the northern and southern hemispheres.
8 If you look at an atlas you will see that there is a lot more land in the northern
hemisphere than in the southern hemisphere, and the southern hemisphere
has a lot more ocean. Does most photosynthesis happen in land plants or in
water plants in the oceans? Explain how you arrived at your answer.
S
knowledge, numeracy
Exploring Science for QCA
Copymaster File 9
127
© Pearson Education Limited 2002