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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