MODULE mod7A mod7B mod7C mod7D mod7E mod7F mod7G mod7H mod7I mod7J mod7K mod7L mod8A mod8B mod8C mod8D mod8E mod8F mod8G mod8H mod8I mod8J mod8K mod8L mod9A mod9B mod9C mod9D mod9E mod9F mod9G mod9H mod9I mod9J mod9K mod9L 9ca1
9Ca1 Measuring photosynthesis 1
Name _____________________________ Class ____________
You are going to try to find out how light affects the amount of photosynthesis.
Prediction
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).
Apparatus
- Elodea pondweed - Glass funnel - Lamp
- Large beaker - Marker pen - Narrow bung
- Pondwater - Ruler - 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.
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.
5 Repeat steps 2 and 3 at various distances between the lamp and the beaker. Write down which distances you choose.
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)
Considering your results/conclusions
Draw a line graph to show your results.
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, _____________________
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. __________________________
[ planning, observing, considering, evaluating ]
9Ca2 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?
- 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.
[ planning ]
9Ca3 Leaves and photosynthesis
Is light needed for photosynthesis? - Instruction Sheet
- Leaves for testing - one that has been in the light and one that has been in the dark
- Iodine solution - Pipette - Scissors
- Bunsen burner - Ethanol - Tripod
- Large beaker - Gauze - Boiling tube
- Heatproof mat - Test tube holder - Eye protection
- Forceps - Petri dish
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.
2 Place both leaves in a beaker of boiling water for one minute.
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.
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.
- 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.
9Ca4 Leaves for photosynthesis 1
Is light needed for photosynthesis?
You will need the instruction sheet 9Ca/3 Leaves and photosynthesis.
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.
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 that are photosynthesising. Photosynthesis only happens in the light.
Starch is made in leaves that are photosynthesising. Photosynthesis only happens in the dark.
Starch is made in leaves that are not photosynthesising. Photosynthesis only happens in the light.
Starch is made in leaves that are not photosynthesising. Photosynthesis only happens in the dark.
[ knowledge, observing, considering ]
9Ca5 Leaves for photosynthesis 2
Is light needed for photosynthesis? Is chlorophyll needed for photosynthesis?
1 Which leaf do you think will have starch in it? Explain why you think this.
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?
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.
9Ca6 Respiration and photosynthesis 1
1 Copy and complete these word equations.
a Photosynthesis:
carbon dioxide + _____________ (+ light energy) → _____________ + glucose
b Aerobic respiration:
oxygen + _____________ → ____________ ____________ + water (+ ___________ )
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?
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.
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?
[ knowledge ]
9Ca7 Respiration and photosynthesis 2
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
This bell jar was placed under a lamp for a week.
This bell jar was placed in the dark 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?
b Describe what you would see when iodine solution was added to each leaf. In each case explain why you think this would happen.
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.
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.
9Ca8 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
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.
[ literacy, knowledge ]
9Ca9 Gas exchange in an oak tree
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.
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 0cm3/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.
[ knowledge, considering, numeracy ]
9Cb1 Leafy matters 1
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
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 cells chloroplasts heat holes large
light losing night oxygen small stomata waterproof
The cuticle is a _______________ layer that stops the leaf _______________too much
water. The palisade cells have lots of _______________ to absorb _______________
energy to make photosynthesis happen. Leaves have a _______________ surface area so
they can absorb a lot of _______________ energy. Cells in the leaf need to absorb
_______________ _______________ from the air. Air gets into the leaf through
_______________ in the bottom surface called _______________ . Guard
_________________ 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.
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 ]
9Cb2 Leafy matters 2
1 The drawing shows a slice through a leaf.
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?
9Cb3 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. Jean-Baptiste van Helmont (1579-1644) did an experiment to show that this was wrong.
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).
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.
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?
9Cb4 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.
The pots were left outside and the masses measured at the end of each day for one week.
Day
0
1
2
3
4
5
6
7
Weather
Cloudy
Sunny
Wet
Sunny & windy
Mass of pot 1 (g)
48
41
39
37
28
21
18
Mass of pot 2 (g)
40.5
39.5
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.
[ knowledge, presenting, considering ]
9Cc1 Adaptations for photosynthesis
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.
3 Name two jobs that stems do.
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? __________________________________________________
______________________________________________________________________
9Cc2 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?
b What is its function?
c How is it adapted to its function?
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.
9Cc3 Carnivorous plants
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.
Watered with nutrient solution including nitrates.
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 (%)
Nitrates available via roots?
Nitrates available via leaves?
100
65
ü
û
145
50
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.
[ considering, research ]
9Cd1 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.
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.
9Cd2 Plants and photosynthesis
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:
- 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.
[ 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
9Cd3 Plants true/false
For each statement, write down whether it is true or false. If it is false, write out a correct version.
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.
12 Plants are important in making carbon dioxide to keep the atmosphere in balance.
9Cd4 Amazon rainforest
This article about deforestation in the Amazon rainforest was published on the New Scientist website in 2001.
Trees toppled
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 12250 square kilometres were logged, compared with 10660 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 Amazonia,' Mary Allegretti, Brazil's secretary of co-ordination for the Amazon, told Reuters.
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.
9Cd5 Plants kriss-kross
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.
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. _____________________________________________
9Cd6 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.
Monitoring stations have been set up all over the world to record the concentrations of different gases in the atmosphere. The graph shows how the concentration of carbon dioxide in the atmosphere changed over four years in the northern and southern hemispheres.
Seasonal changes in atmospheric CO2.
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.
[ knowledge, numeracy ]