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Boardworks GCSE Additional Science: Biology Photosynthesis

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Presentation on theme: "Boardworks GCSE Additional Science: Biology Photosynthesis"— Presentation transcript:

1 Boardworks GCSE Additional Science: Biology Photosynthesis

2 Boardworks GCSE Additional Science: Biology Photosynthesis

3 What are plants used for?
Boardworks GCSE Additional Science: Biology Photosynthesis How many different uses of plants can you spot? Teacher notes This illustration contains several discussion points about the uses of plants and the importance of photosynthesis, including: sunshine: essential for photosynthesis man watering the plants: water is used by plants for photosynthesis basketball: traditionally made from the sap of the rubber plant basketball net: rope can be made from plant fibres, such as jut and hemp scoreboard: made from wood aspirin (given to the man rubbing his head): contains acetylsalicylic acid, which is derived from salicin, a compound found in willow bark barbeque: uses charcoal bricks, a wood product sausage (at the barbeque): made from animals that eat plants foxgloves (tall purple plants in background): contain digitalis, a compound used to treat heart problems tortilla chips: made from maize flour, a type of cereal popcorn: made by heating dried maize kernels sugar snaps: made from sugar cane banana: fruits are one type of glucose store made by plants paper packaging: originally made from papyrus, paper is now made from wood pulp roses (in background): these flowers are often given as presents. rabbits: plants provide food for all animals, directly or indirectly cotton clothing: made from cotton fibres synthetic clothes and plastic bottle: products made from oil and other fossil fuels originally come from ancient plants and animals.

4 Boardworks GCSE Additional Science: Biology Photosynthesis
Using plants Boardworks GCSE Additional Science: Biology Photosynthesis Photo credits: © 2007 Jupiterimage Corporation Teacher notes This activity provides illustrated information about the uses of plants. It could be used as a stimulus to start a wider discussion on the uses of plants, or to help emphasis the importance of photosynthesis in a wider context. More information about digitalis is available at

5 How do plants get the food they need?
Boardworks GCSE Additional Science: Biology Photosynthesis All living organisms need food to grow and survive. This is because food provides raw materials for growth and energy for chemical reactions. Plants are known as producers because they provide food for many other organisms. Without plants, other organisms would have no raw materials for growth or energy. Unlike animals, plants cannot move very much, so how do they get the food that they need?

6 Boardworks GCSE Additional Science: Biology Photosynthesis
Do plants eat soil? Boardworks GCSE Additional Science: Biology Photosynthesis It used to be thought that plants got their food from the soil. This was proved to be untrue by measuring the mass of the soil in a plant pot before and after growth. The soil did not decrease in mass, even though plant mass increased. Later experiments showed that plants actually make their own food! Plants are the only living organisms that can do this. This means that all other organisms rely on plants. What is the name of the process by which plants make food?

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8 What is photosynthesis?
Boardworks GCSE Additional Science: Biology Photosynthesis Plants make their own food by photosynthesis. This process is a chemical reaction that uses light energy. light energy The word photosynthesis comes from the Greek language: ‘photo’ means ‘light’ ‘synthesis’ means ‘putting together’ Photosynthesis just means ‘putting together with light’.

9 Boardworks GCSE Additional Science: Biology Photosynthesis
Teacher notes This five-stage interactive animation shows how photosynthesis occurs in leaves. At the end of the animation, you can view a summary of this process by clicking on “summary”. Suitable prompts could include: Start: What is so special about photosynthesis? Stage 1: Where in the plant does photosynthesis take place? Stage 2: Which material comes from the soil and which material comes from the air? Why does carbon dioxide enter the plant from underneath the leaf? Stage 3: What is the source of the light energy for photosynthesis? Stage 4: Where in the plant cell does photosynthesis take place? What is the name of the pigment that is needed for photosynthesis? Stage 5: What food is produced during photosynthesis? What gas is produced during photosynthesis?

10 Photosynthesis: summary
Boardworks GCSE Additional Science: Biology Photosynthesis How can the process of photosynthesis be summarized in one sentence? Photosynthesis is a chemical reaction that takes place in the chloroplasts of green plant cells, where light energy is used to convert carbon dioxide and water into glucose and oxygen. What is the word equation for this chemical reaction? light energy chlorophyll carbon dioxide + water oxygen glucose

11 Photosynthesis: word equation activity
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This drag and drop activity could be used as a plenary exercise to check students’ ability to identify the reactants, conditions and products of photosynthesis.

12 What is the symbol equation for photosynthesis?
Boardworks GCSE Additional Science: Biology Photosynthesis The reaction of photosynthesis can be represented by the following equation: light energy chlorophyll carbon dioxide + water oxygen glucose What is the symbol equation for this reaction? light energy 6 CO2 + 6 H2O C6H12O2 + 6 O2 chlorophyll Is this a balanced symbol equation? How would you balance the equation?

13 Word equation to symbol equation
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This drag and drop activity could be used to extend the work on the photosynthesis equation, by providing practise of changing the word equation into a balanced symbol equation. It is important to highlight that chlorophyll and light energy are still represented by words in the symbol equation.

14 Photosynthesis equation quiz
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This multiple-choice quiz of ten questions could be used as a plenary activity to check students’ understanding of photosynthesis. To answer the questions, students select the appropriate component of the photosynthesis word equation. Mini-whiteboards could be used to make this a whole class activity.

15 Does photosynthesis change the air?
Boardworks GCSE Additional Science: Biology Photosynthesis The evolution of photosynthesis, hundreds of millions of years ago, was one of the biggest changes to shape the Earth. Photosynthesis by plants caused major alterations to the atmosphere of Earth, turning it from a hot and hostile planet into one suitable for life. It lowered the levels of carbon dioxide in the atmosphere and raised the levels of oxygen, which is used by most organisms for respiration. Oxygen also lead to the formation of the ozone layer, which filters out harmful UV rays. Photo credit: U.S. Fishing and Wildlife Service. Image shows Californian forest. Teacher notes This slide could be used to emphasize the connection between photosynthesis and the atmosphere of Earth. The importance of oxygen, the waste product of photosynthesis, could be highlighted. See the Boardworks GCSE Science (Chemistry) ‘Earth’s Atmosphere’ presentation for more information on the evolution of the atmosphere.

16 Why are plants important to climate change?
Boardworks GCSE Additional Science: Biology Photosynthesis Carbon dioxide is a greenhouse gas. This means it traps heat from the Earth and stops it escaping into space, like a pane of glass in a greenhouse. Burning fossil fuels, increased travel and deforestation have caused atmospheric carbon dioxide levels to rise dangerously high. This is causing the Earth to overheat, melting the ice caps and endangering species. Teacher notes This slide could be used to emphasize the importance of plants and photosynthesis to balance the level of carbon dioxide in the atmosphere. See the Boardworks GCSE Science (Chemistry) ‘Climate Change’ presentation for more information on the carbon cycle, climate change and global warming. Photosynthesis converts carbon dioxide into storable sugars and oxygen. Planting more trees could help reduce the amount of carbon dioxide in the atmosphere.

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18 Boardworks GCSE Additional Science: Biology Photosynthesis
How is glucose used? Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This activity provides illustrated information about how glucose is used by a plant. It could be used to introduce the topic or for revision purposes.

19 How can you test for photosynthesis?
Boardworks GCSE Additional Science: Biology Photosynthesis The presence of starch in a leaf can be used to show that photosynthesis has taken place. Iodine is used to test for starch. It reacts with starch and changes colour from brown to blue-black. The starch test can be used to prove that photosynthesis needs light, carbon dioxide and chlorophyll to take place. How would you set up an experiment to test the conditions needed for photosynthesis? How would you make the experiment fair and reliable?

20 Testing leaves for starch
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This four-stage virtual experiment demonstrates how iodine can be used to test for starch. It could be used as a precursor to running the practical in the lab, or as a revision exercise. Suitable prompts include: Stage 1: Why is the leaf placed in boiling water? Stage 2: What does the warm alcohol do to the leaf? Stage 3: Why is the leaf placed in warm water? Stage 4: What colour change occurs if starch is present?

21 Is chlorophyll needed for photosynthesis?
Boardworks GCSE Additional Science: Biology Photosynthesis Chlorophyll cannot be removed from a plant without killing the plant. Instead, variegated leaves can be used to show chlorophyll is essential for photosynthesis. Variegated leaves have pale parts, which do not contain chlorophyll. The green parts of the leaf contain chlorophyll and are the control. Which areas will react with iodine? Only the green areas of the leaf react with the iodine and turn blue-black. Without chlorophyll, the pale areas have been unable to produce starch and do not turn blue-black.

22 Testing leaves for starch – activity
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This activity can be used as a plenary or revision exercise to test students’ understanding of the conditions required for photosynthesis. The activity consists of two parts: Students complete the final stage of the iodine test on five leaves Students identify the conditions of growth for each plant. It should be highlighted to students that before putting a plant in experiment conditions, the plant should be de-starched. This can be done by putting the plant in darkness for approximately two days. This means that starch present in the leaves has been produced during the experiment.

23 Boardworks GCSE Additional Science: Biology Photosynthesis

24 What is the rate of photosynthesis?
Boardworks GCSE Additional Science: Biology Photosynthesis Photosynthesis is a chemical reaction and so has a rate. Like many reactions, photosynthesis requires enzymes. Is the rate of photosynthesis always the same? Which factors do you think affect the rate of photosynthesis? light carbon dioxide temperature How do these factors affect the rate of photosynthesis?

25 How does light affect photosynthesis?
Boardworks GCSE Additional Science: Biology Photosynthesis Light energy has to be absorbed by chlorophyll for photosynthesis to take place. light energy chlorophyll carbon dioxide + water oxygen glucose The brighter the light, the more light energy there is, so will photosynthesis be faster or slower? More light energy means that photosynthesis will be faster. If light intensity is too high plant cells can be damaged. How is photosynthesis affected if this happens?

26 Investigating photosynthesis – apparatus
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This equipment preparation activity illustrates the apparatus need to test the rate of photosynthesis. It could be used as a precursor to running the practical in the lab, or as a revision exercise.

27 Investigation photosynthesis - experiment
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This virtual experiment illustrates how light intensity affects the rate of photosynthesis. It could be used as a precursor to running the practical in the lab, or as a revision exercise. When using this activity, it should be emphasized that more oxygen is being produced when the light intensity is increased. This is shown by the rate of production of gas bubbles.

28 Investigation photosynthesis – results
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This data handling activity investigates the affects of light and temperature on the rate of photosynthesis. Students are able to plot two graphs using experimental data and a line of best fit is automatically added to each graph. It could be used to compliment a practical in the lab, or as a revision exercise. While using the activity, it should be emphasized that two experiments were conducted, changing only one variable at a time.

29 Carbon dioxide and the rate of photosynthesis
Boardworks GCSE Additional Science: Biology Photosynthesis Carbon dioxide is one of the raw materials used by plants to make their food. light energy chlorophyll carbon dioxide + water oxygen glucose The concentration of carbon dioxide in the air is actually quite low (0.03%) . Why is the concentration of carbon dioxide in commercial greenhouses often raised to about 0.1%? More carbon dioxide means more photosynthesis, so plants make more food and grow more quickly.

30 Does temperature affect photosynthesis?
Boardworks GCSE Additional Science: Biology Photosynthesis Photosynthesis is controlled by enzymes, which usually work best at warmer temperatures. Does increasing the temperature always increase the rate of photosynthesis? If it gets too hot (above 40 °C), the enzymes needed for photosynthesis begin to break down and are destroyed or denatured. The rate of photosynthesis decreases or even stops completely. Photo credit (both images): © 2007 Jupiterimage Corporation Teacher notes See the ‘Enzymes’ presentation for more information about temperature and enzymes.

31 What is a limiting factor?
Boardworks GCSE Additional Science: Biology Photosynthesis What is the ideal combination of factors for the maximum rate of photosynthesis? enough light enough carbon dioxide ideal temperature (not too hot or cold). How does restricting one of these facts affect the rate? If one of the factors is restricted, the rate of photosynthesis will be below the maximum possible rate. The restricted factor controls how quickly photosynthesis occurs and so limits the rate. It is called the limiting factor.

32 Light intensity and photosynthesis
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This animated graph illustrates the affect of light intensity on the rate of photosynthesis. It should be emphasized that after a certain point, other limiting factors will control the rate and further increasing light intensity will have no effect.

33 Carbon dioxide and photosynthesis
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This animated graph illustrates the affect of carbon dioxide levels on the rate of photosynthesis. It should be emphasized that after a certain point, other limiting factors will control the rate and increasing carbon dioxide levels will have no effect. The similarities of the light intensity and carbon dioxide graphs could also be highlighted.

34 Temperature and photosynthesis
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This animated graph illustrates the affect of temperature on the rate of photosynthesis. It should highlighted that, unlike carbon dioxide and light intensity, increasing the temperature above 45 ºC will cause the rate to decrease or stop completely. Students should be aware that photosynthesis is controlled by temperature-sensitive enzymes. At both stages of the graph, temperature is the limiting factor. See the ‘Enzymes’ presentation for more information about temperature and enzymes.

35 Limiting factors – activity
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This labelling graphs activity could be used to check students’ understanding of factors that limit the rate of photosynthesis. It should be emphasized that each of the three factors could possibly limit photosynthesis.

36 Limiting factors in a greenhouse
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This simulation activity enables students to experiment with the conditions required for optimum plant growth. It could be used as a plenary activity to check students’ understanding of the factors that control photosynthesis, or as a revision exercise.

37 Boardworks GCSE Additional Science: Biology Photosynthesis

38 How do leaves maximise photosynthesis?
Boardworks GCSE Additional Science: Biology Photosynthesis Leaves are the most efficient solar panels on Earth! What does this mean? Like solar panels, leaves convert energy from the Sun into usable chemical energy. Although leaves come in a variety of shapes and sizes, they share certain features that enable the plant to maximize photosynthesis.

39 How are leaves adapted for photosynthesis?
Boardworks GCSE Additional Science: Biology Photosynthesis To increase photosynthesis, leaves have certain key features: thin – this allows gases to reach cells easily wide and flat – this create a large surface area to absorb as much light as possible veins – these carry water to the cells and carry glucose away and also support leaves stomata – these are pores on the underside of leaves through which gases move in and out.

40 Structure of a leaf activity
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This matching activity could be used as a plenary or revision exercise on the adaptations of leaves for photosynthesis. Students could be asked to complete the question in their books and the activity could be concluded by the completion on the IWB.

41 Take a look inside a leaf
Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This animated zoom activity allows students to investigate how leaves are adapted to photosynthesis on a cellular level. Students could be asked to draw a similar labelled diagram in their books.

42 How do gases enter and leave plants?
Boardworks GCSE Additional Science: Biology Photosynthesis On the underside of leaves are small holes, or pores, called stomata. A single hole is called a stoma. Each stoma is surrounded by two guard cells. When guard cells gain water, they curve outwards. This opens the stoma, allowing gases in and out. Losing water causes the guard cells to come closer together, closing the stoma. This stops the movement of gases, but also prevents water loss.

43 Boardworks GCSE Additional Science: Biology Photosynthesis
Leaf adaptations Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This activity provides illustrated information about how plants are adapted to specific environments. It could used to stimulate discussion about what plants need to survive and how they are adapted to balance these needs.

44 Boardworks GCSE Additional Science: Biology Photosynthesis

45 Boardworks GCSE Additional Science: Biology Photosynthesis
Glossary (1/2) Boardworks GCSE Additional Science: Biology Photosynthesis cellulose – An insoluble carbohydrate made from glucose. It is used to make cell walls. chlorophyll – The green pigment inside chloroplasts that is needed for photosynthesis to take place. chloroplast – The plant cell structure where photosynthesis occurs. cuticle – A waxy layer on the surface of the leaf that prevents water loss. epidermis – A protective outer layer of cells found on the top and underside of leaves. This layer is clear to allow photosynthesis. guard cells – A pair of cells that control the opening and closing of a stoma (single hole).

46 Boardworks GCSE Additional Science: Biology Photosynthesis
Glossary (2/2) Boardworks GCSE Additional Science: Biology Photosynthesis palisade – A layer of cells in the leaves, which contain lots of chloroplasts. It is the main site of photosynthesis. photosynthesis – The process by which plants use carbon dioxide and water to make glucose and oxygen in the presence of light and chlorophyll. spongy layer – A layer of cells that contains large spaces between cells. This allows the diffusion of gases between the stomata and palisade layer. stoma (singular) – A single hole on the lower surface of the leaf that allows gases in and out. stomata (plural) – Small holes in the lower surface of leaves that allow gases in and out. variegated – A leaf containing areas without chlorophyll.

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Anagrams Boardworks GCSE Additional Science: Biology Photosynthesis

48 Boardworks GCSE Additional Science: Biology Photosynthesis
Multiple choice quiz Boardworks GCSE Additional Science: Biology Photosynthesis Teacher notes This multiple–choice quiz could be used as a plenary activity to assess students’ understanding of photosynthesis. The question can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their book and the activity could be concluded by the completion on the IWB.


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