Cambridge IGCSE Biology Teacher's Resource (third edition)

This Teacher’s Resource contains a range of materials designed to support teaching of the syllabus. Its content has been revised and rearranged, ensuring that it is up to date and comprehensive in its coverage, with new material covered. A Coursebook and Workbook are also available.

The Teacher’s Resource contains: • editable teaching notes for each chapter, including lesson plans, common misconceptions and homework ideas • a collection of editable practical activities, with accompanying teacher’s/technician’s guidance notes • editable Worksheets and answers organised by chapter • answers to end-of-chapter questions from the Coursebook • answers and workings to the exercises from the Workbook • model exam papers and mark schemes • animations.

Other components of IGCSE Biology, Third edition: ISBN 978-1-107-61479-6 Coursebook Workbook ISBN 978-1-107-61493-2

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Mary Jones and Geoff Jones

Cambridge IGCSE®

Biology Teacher’s Resource

Third edition

Jones and Jones

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Biology Teacher’s Resource

9781107614963 Cambridge IGCSE Biology Teacher’s Resource Mary Jones and Geoff Jones. C M Y K

Cambridge IGCSE Biology, Third edition matches the requirements of the latest Cambridge IGCSE Biology syllabus (0610). It is endorsed by Cambridge International Examinations for use with their examination.

Cambridge IGCSE

Cambridge IGCSE Biology, Third edition Teacher’s Resource Mary Jones and Geoff Jones

ISBN 978-1-107-61496-3

9 781107 614963

9781107614963cvr.indd 20

Original material © Cambridge University Press 2014

12/09/2013 16:06

Teaching ideas These teaching notes are intended to provide outline ideas for ways in which you might cover the IGCSE Biology syllabus with your students. They do not provide a complete scheme of work, nor lesson plans. They are simply suggestions, some of which you might like to incorporate into your lessons.

It is most important to remember that biology is not just a body of knowledge. Biology is a science, and students should be made constantly aware that research is ongoing and continues to surprise us with new findings, some of which contradict what we thought we already knew. They need to become familiar with scientific method. They should be asked to make careful observations and record them, to display, analyse and interpret results, to evaluate the reliability of results and to plan and evaluate their own experiments. The activities in the Coursebook, exercises in the Workbook and the worksheets supplied as part of this Teacher’s Resource provide many opportunities for developing these skills, and you will probably also like to add some of your own.

The notes for each chapter begin with a table suggesting a possible way of breaking up the material to be covered into a number of topics. The number of lessons you might spend on each topic is given as a range, because it will depend very much on what students have done before, and also on how much time you decide to spend on providing students with opportunities to develop skills such as data-handling or planning experiments. For each topic, relevant resources in the Coursebook, Workbook and worksheets are listed.

Outline descriptions of what might be included in lessons covering each topic are then given. These are no more than suggestions, and they are not comprehensive. You may like to use all of them, some of them or none of them. Most indicate ways in which students can become actively involved in their learning, rather than passively absorbing information.

There is also a list of some of the most common misunderstandings and misconceptions that are regularly seen in students’ answers, and some suggestions for tasks that could be set for homework.

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Introduction: Teaching ideas

1

Teaching ideas Chapter 1

Classification

Syllabus sections covered: 1.1 to 1.4

Teaching resources Syllabus section

Topic

40-minute periods

Resources in Coursebook

1.1

Characteristics of living things

1

EOCQ 1

1.2

Concept and use of a classification system

1

Question 1.1

The kingdoms of living organisms

2 to 4

1.3 (part)

Resources in Workbook

Resources on this CD-ROM Worksheet 1.1 Characteristics of living organisms

EOCQ 2

Viruses

Activity 1.1 Making biological drawings Questions 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 EOCQ 3

1.3 (part)

Classifying animals; Classifying plants; magnification

2 to 4

Activity 1.2 Calculating magnification

Exercise 1.1 Observing and drawing organisms

Worksheet 1.2 Characteristics of vertebrates

Exercise 1.2 Using keys

Worksheet 1.3 Writing a key

EOCQs 5, 6 1.4

Keys

1 to 2

Question with Fig. 1.20 EOCQ 4

Topic 1

Characteristics of living things

Coursebook section 1.1 Teaching ideas Many students are likely to already have some knowledge of the characteristics of living organisms. It is a good idea to try to draw these out from them, rather than simply telling them what the characteristics are. Some examples of ways you might do this are outlined below. ◆

Hold a living plant, an animal (or yourself) and a non-living object (for example, a kettle) where all students can see them. Ask students to suggest characteristics that the animal and the plant share, but which the non-living object does not have. Build up a list on the board.

Original material © Cambridge University Press 2014

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Chapter 1: Teaching ideas

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◆

Alternatively, settle students into groups, and ask the groups to suggest a list of seven characteristics of all living organisms. Then ask one member of each group to feed back their ideas to the rest of the class. ◆ Make several sets of cards, each with a process written on it. Include the seven characteristics of living organisms, and also some others that could be mistaken by students – for example, ‘possessing a blood system’, ‘having a brain’. Hand out a set of cards to each group, and ask students to sort them into characteristics that all living organisms share, and those that are possessed by only some living organisms. It may be best not to worry too much about defining each term in the list at this stage, as students are more likely to retain this knowledge when they cover each process in more detail. However, if you would like to deal with this in this lesson, you could have a second set of cards with definitions of each process, and ask the groups to match each process card with a definition card. ◆ Challenge students to explain why a moving car is not a living organism, even though it needs nutrients (fuel), releases energy through chemical reactions (between oxygen and fuel), can respond to stimuli (for example, the driver’s foot on the brake pedal) and can move. ◆ Ask students if they think there is life on other planets. If so, would it have to show all of the characteristics of life here on Earth? ◆ End the lesson with a quick spelling quiz. Read out each of the seven characteristics, plus the other new terms introduced, and give a short time (say 15 seconds) to write each one down. This is probably best done in small groups, where the better spellers can work with weaker ones.

Common misunderstandings and misconceptions ◆ ◆

Students often think only of animals when listing characteristics of living organisms.

They may think that plants cannot move. Explain the difference between movement and locomotion. If possible, show them an example of movement in a plant. ◆ Excretion may be confused with egestion. Students may think that plants do not excrete. Remind them that they get rid of oxygen from their leaves when they are photosynthesising. Old leaves, containing excretory substances, may be dropped from a plant. They will look at this difference again when they study the digestive system and the kidneys. ◆ Respiration may be confused with breathing or gas exchange. ◆ Any one living organism does not have to carry out all the processes all the time. So, for example, the students are not reproducing at this moment, but humans as a species have the capacity to reproduce.

Homework ideas ◆ ◆

Worksheet 1.1 Characteristics of living organisms Think of a mnemonic for the seven characteristics of living things. Bring to the next lesson, when the class votes for the best one, which then goes up on the wall. ◆ Explain why a car is not a living organism. ◆ Make a set of revision flash cards with a characteristic of living things on one side and the definition on the other. ◆ Design a living organism that lives on another planet, but which shows all the characteristics of living things. ◆ Research different ways in which plants can move. ◆ End-of-chapter question 1 Original material © Cambridge University Press 2014 © Cambridge University Press 2014

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Topic 2

Concept and use of a classification system

Coursebook section 1.2 Teaching ideas ◆

Sit students in groups and give each group a set of objects (you will probably get more out of this exercise if each group has a similar set), which could be grouped in different ways — for example, seeds and beads of different colours and shapes. Ask each group to choose a way of classifying them (by colour, shape, living or non-living, and so on).

Use leading questions to encourage discussion: What features did they use for their classification? Why is it helpful to classify things? Which method of classifying these objects do they think is the most useful? (The answers should bring out the point that the way you classify objects depends on why you are classifying them. You might classify objects in a different way if you intend to make jewellery with them than if you intend to eat them, for example.) Lead the discussion towards reasons why biologists classify living organisms. ◆ Show students two organisms or pictures of two organisms, that have the same common name but that are clearly not the same. Alternatively, or as well, show them an organism that has different names in different places or countries. Examples should be taken from the local environment if at all possible. Discuss with the students why it might matter if people misunderstand each other when discussing a particular kind of animal or plant, and lead them towards the idea of having one name for each species that is used all over the world. ◆ Explain the binomial system of naming organisms, using Figure 1.3, or your own local examples of organisms, to illustrate this. ◆ For students studying the Supplement, you might like to discuss the use of DNA in classification here. Alternatively, you could leave this until you have covered the structure of DNA in Chapter 4, when it will be much easier for students to understand. ◆ Do question 1.1 as a class exercise.

Common misunderstandings and misconceptions ◆

You will often see Latin names written incorrectly in the media – for example, without the use of a capital letter for the generic name, and students may not realise that this is wrong.

Homework ideas ◆

End-of-chapter question 1.2

Topic 3 The kingdoms of living organisms: viruses Coursebook sections 1.3 and 1.4 Teaching ideas Note that Core students need only know about the animal and plant kingdoms. You might be able to cover this quite quickly, and move on to the next topic in the same lesson. ◆

Show students at least one example of each of the five kingdoms: an animal (including themselves, and some animals other than mammals), a plant (including a non-flowering plant, such as a moss), a fungus (perhaps a mushroom and a mould), and photographs of bacteria.

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◆

Use this as an opportunity to ask students to recall the characteristics of living organisms, shared by all of these organisms. ◆ Use Coursebook pages 6 to 8 and your examples to discuss the characteristic features of each kingdom. ◆ For Supplement students, you could also cover viruses in this lesson, using the information on page 9. It is difficult for students to appreciate, so early in their course, why viruses are not normally classified as living organisms (and certainly do not belong to any of the five kingdoms), but this can be dealt with as a discussion.

Common misunderstandings and misconceptions ◆

Students often use the word ‘animal’ to mean ‘mammal’.

Homework ideas ◆

End-of-chapter question 3

Topic 4

Classifying animals and plants: magnification

Coursebook sections 1.5, 1.6.

Teaching ideas ◆

Set out a ‘circus’ of specimens and photographs representing each of the groups of vertebrates, as described on Coursebook pages 9 and 10. Hand out Worksheet 1.2 and ask students to complete this. Bring the class together, and discuss the features that can be used to classify vertebrates into these classes. ◆ A similar approach could be taken to deal with the classification of arthropods. It would also be good to take students outside to look for arthropods – it is usually very easy to find examples of ‘small animals with legs’ such as spiders, insects and millipedes. ◆ Ask students to make a large, labelled drawing of one or more of the animals used in the circus, or that they have found. Activity 1.1 in the Coursebook could be used here, and/ or Workbook exercise 1.1, where the self-assessment sheet could be used to help students focus on what is required from a biological drawing. Use their drawings to explain the concept of magnification. Activity 1.2 could also be done. Note that magnification will be revisited in Chapter 3. ◆ Classification of plants could be dealt with in a similar way to vertebrates and arthropods.

Note that only ferns and flowering plants are required; flowering plants can then be identified as monocots or dicots. You should try to provide living examples for students to see and handle, or – even better – take them outside to find the plants growing.

Common misunderstandings and misconceptions ◆

It is very common for students to confuse the characteristic features of one class of arthropods (e.g. insects) with the characteristic features of arthropods in general.

Homework ideas ◆ ◆

Activity 1.2 Calculating magnification End-of-chapter-questions 5 and 6

Original material © Cambridge University Press 2014 © Cambridge University Press 2014

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Topic 5

Keys

Coursebook section 1.7 Teaching ideas ◆

Students normally find using a dichotomous key very easy. Show them how to use the key on page 15 in the Coursebook. Then provide a key that you have written yourself to enable the identification of different kinds of trees that grow in your school grounds. Ideally, allow the students to go outside to identify selected trees; otherwise, bring small branches or individual leaves into the classroom. (For future lessons, you may be able to use keys that your students have written in previous years.) ◆ Students could then be asked to construct their own keys. Worksheet 1.3 provides material for this, and so do Figure 1.23 and end-of-chapter question 4. It would also be an excellent idea to ask students to construct keys to identify a small range of animals or plants that can be found in the school grounds.

Common misunderstandings and misconceptions ◆

Students may try to use a key by looking at all the organisms at once and trying to match them against descriptions, rather than looking at just one organism and working systematically through the key to identify it. ◆ When writing keys, they may use terms such as ‘long’ or ‘dark’, which are subjective and therefore not useable by a person looking at just one type of organism. All descriptions should be objective, as explained on Coursebook page 16.

Homework ideas ◆ ◆ ◆ ◆ ◆

Workbook exercise 1.2 Using keys Worksheet 1.3 Writing a key Question in the caption of Figure 1.23 in the Coursebook End-of-chapter question 4 Construct a key to identify the leaves of five trees that grow in the school grounds

Original material © Cambridge University Press 2014 © Cambridge University Press 2014

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Teaching ideas Chapter 2

Cells

Syllabus sections covered: 2.1, 2.2, 2.3

Teaching resources Syllabus section

Topic

40-minute periods

Resources in Coursebook

Using a microscope

2

Activity 2.1 Using a microscope

Resources in Workbook

Worksheet 2.1 The parts of a microscope

Questions 2.1, 2.2 2.1

Cell structure and organisation

3–6

Activity 2.2 Looking at animal cells

Exercise 2.1 Animal and plant cells

EOCQs 3, 4

Exercise 2.2 Drawing cells and calculating magnification

Questions 2.3 to 2.19 Activity 2.3 Looking at plant cells 2.2

Cells and organisms

1

Topic 1

Using a microscope

Resources on this CD-ROM

Worksheet 2.2 Cell structure Worksheet 2.3 Magnification calculations

Exercise 2.3 Organelles

EOCQs 1, 2, 5

Coursebook section 2.1 Teaching ideas ◆

Ascertain how familiar students are with using a microscope. If they are already competent in this skill, you can move straight on to the next topic. ◆ Show students the microscopes that you have in your laboratory, and demonstrate how to use one. You could use Worksheet 2.1 The parts of a microscope, to check they know the names of the different parts. ◆ Ask students to do Activity 2.1 Using a microscope. Students could then make temporary slides of drops of pond water, or moss leaves. If you have suitable equipment, you could project images from a microscope onto a screen.

Common misunderstandings and misconceptions ◆

There are no common misunderstandings associated with this topic.

Homework ideas ◆

Worksheet 2.1 The parts of a microscope Original material © Cambridge University Press 2014

© Cambridge University Press 2014 IGCSE Biology

Chapter 2: Teaching ideas

1

Topic 2

Cell structure and organisation

Coursebook section 2.1 Teaching ideas ◆

Ascertain how familiar students are with the structure of animal and plant cells. If they already have good knowledge of them you may be able to move quickly through this topic. ◆ Project a large image of some cells onto a screen. Ask students what they are. Ask them to try to identify the different parts. Ask them how big they think cells really are. Tell them that a large cell may be about 0.1 mm long, and ask them to look at a ruler and imagine 10 cells side by side between two of the millimetre marks. ◆ Revise the concept of magnification. Coursebook questions 2.3 to 2.5 could be done as a class discussion, or as group work. ◆ Students could make model cells, using a plastic bag (cell membrane), water or jelly (cytoplasm) and a small rubber ball (nucleus). Put the whole thing inside a cardboard box to represent the cell wall of a plant cell. Challenge students to suggest how they could add chloroplasts and vacuole to the plant cell model. ◆ Discuss and explain the structure of animal cells. Students could carry out Activity 2.2 Looking at animal cells. They could exchange their drawings with one another, and mark them using the self-assessment check list for drawing (on the student CD-ROM). Discuss any difficulties that students had with this activity, and how they solved them. ◆ Use a similar approach to deal with the structure of plant cells. You could perhaps begin by drawing a rectangle on the board, and asking pupils to come to the front and complete the diagram to show the structures in a plant cell. Activity 2.3 Looking at plant cells, could be carried out. (You will need to demonstrate how to obtain and mount the piece of onion epidermis.) ◆ Students should now have enough information to be able to construct their own comparison of features found in animal cells and plant cells. This could possibly be done as a class or group activity. ◆ Coursebook questions 2.6 to 2.19 can now be answered.

Common misunderstandings and misconceptions ◆

Students frequently confuse cell membrane and cell wall.

Homework ideas ◆ ◆ ◆ ◆ ◆

Worksheet 2.2 Cell structure Worksheet 2.3 Magnification calculations Workbook exercise 2.1 Animal and plant cells Workbook exercise 2.2 Drawing cells and calculating magnification Workbook exercise 2.3 Organelles

Topic 3

Cells and organisms

Coursebook section 2.2

Original material © Cambridge University Press 2014 © Cambridge University Press 2014

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Teaching ideas ◆

Discuss the idea that there are many different kinds of cell in an organism such as an animal or plant. (It is suggested that you wait to cover the detailed structure of the cells listed in Section 2.2 in the syllabus until you reach the topics where the functions of these specialised cells are covered.) Introduce the ideas of tissues, organs and organ systems.

Ensure that students know they need to learn these definitions.

Common misunderstandings and misconceptions ◆

Students with Spanish as their first language often seem to use the term ‘organism’ to mean ‘body’ (for example, ‘It is bad for your organism to eat too much fat’), which is incorrect.

Homework ideas ◆

End-of-chapter questions 1, 2 and 5

Original material © Cambridge University Press 2014 © Cambridge University Press 2014

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Teaching ideas Chapter 3

Movement in and out of cells

Syllabus sections covered: 3.1, 3.2, 3.3

Teaching resources Syllabus section

Topic

40-minute periods

Resources in Coursebook

Resources in Workbook

3.1

Diffusion

2 to 3

Questions 3.1 to 3.3

Exercise 3.1 Diffusion experiment

Activity 3.1 Demonstrating diffusion in a solution

Resources on this CD-ROM

Activity 3.2 Investigating factors that affect the rate of diffusion Activity 3.3 Diffusion of substances through a membrane EOCQ 4 3.2

Osmosis

3 to 6

Questions 3.4 to 3.15 EOCQs 1, 2, 3 Activity 3.4 Investigate and describe the effects on plant tissue of immersion in different solutions

Exercise 3.2 How plants take up water

Worksheet 3.1 Drying mangoes

Exercise 3.3 Osmosis and potatoes

Activity 3.5 Measuring the rate of osmosis Activity 3.6 Osmosis and potato strips 3.3

Active transport

Topic 1

Diffusion

1 to 2

EOCQ 4

Exercise 3.4 Diffusion and active transport

Worksheet 3.2 Diffusion, osmosis and active transport

Coursebook section 3.1

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

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Teaching ideas ◆

It is worth checking students’ understanding of particle theory, which they may have covered in earlier science lessons. Before they can understand diffusion or osmosis, they must understand: – the concept of particles moving randomly – the terms ‘molecule’, ‘atom’ and ‘ion’ – that a solution contains particles of a solute dispersed in a solvent.

If you are concerned about any of this, you could try setting students a short verbal or written test (for example, 10 multiple-choice questions), so that you can discover early on if you need to spend time on these concepts. ◆ Activity 3.1 Demonstrating diffusion in a solution, could provide a good starting point.

You could set this up as a demonstration (involving students in setting up the apparatus if possible) near the beginning of the lesson, and return to it at the end. Alternatively, students could do Activity 3.1 themselves, in small groups. If possible, leave the apparatus until next lesson before recording results. ◆ If you can take your class into a space where they can move around freely – a hall, playground or sports field, for example – they can act as though they were gas particles.

Ask them to stand in one spot in one small part of the room, approximately equally spaced from each other and not touching (that is, like the particles in a gas). Each student then moves in a randomly chosen direction in a straight line. They only change course when they hit a wall of their ‘container’, or another particle, in which case they bounce off and travel in a straight line in a different direction. After a short while, stop the students, asking them to stand still and tell you what has happened – they should have spread into all the available space and be approximately evenly distributed. You could repeat the exercise as though they were particles in a liquid – in this case, they should hold out their hands and always be lightly touching another ‘particle’ as they move. ◆ Ask students to make suggestions of instances where diffusion is important to living organisms. There are several mentioned on page 29 in the Coursebook. ◆ Activity 3.2 is a planning exercise. Demonstrate the technique of using agar jelly and an alkali to measure diffusion. If your class has had no experience of planning experiments before, you should do this as a class exercise, discussing with them what they need to think about as they plan. It is recommended that you use the terms independent variable and dependent variable, and consider all of the variables that should be kept constant. If the class already has experience of planning their own experiments, this could be done as group work, with different groups investigating different independent variables. ◆ Activity 3.3 is well worth carrying out. It introduces the idea of diffusion through microscopic holes in a membrane, which can be built on when you move on to discuss osmosis. ◆ Show students some Visking tubing, and explain that it has molecule-sized holes in it, much too small for them to see. Show them how to moisten and open the tubing.

They can then set up the apparatus for themselves. They should begin to get results quite swiftly. They may be able to begin writing up their experiment while they are waiting for their final results. When everyone has results, lead a discussion about them: What did they see? What does this mean? How did the iodine get into the starch solution?

Why didn’t the starch get into the iodine solution? What do they think the water molecules were doing? This is an opportunity to emphasise that each ‘particle’ is moving on its own; they should be thinking about iodine particles and water particles, not ‘iodine solution’, when considering what is moving Original material © Cambridge University Press 2014 © Cambridge University Press 2014

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◆

If you plan to set Workbook exercise 3.1 Diffusion experiment, as homework, you may like to show students a Petri dish containing agar jelly, make some holes in the jelly and add some coloured solution to it. Depending on the students’ previous experience, you may also need to discuss how to calculate means. This is also a good opportunity to think about what is meant by a hypothesis, and how an experiment can be set up to test one.

They will also need to think about variables. They do not need to know the terms ‘dependent variable’ (what they measure) and ‘independent variable’ (the parameter that they change, in this case the temperature) but you may find it helpful to use these terms.

Check what is done in chemistry and physics lessons. Students will also need to think about sources of experimental error, and not confuse these with ‘mistakes’. In this case, the main source of error is likely to be in deciding exactly where the ‘edge’ of the colour is in the agar, so that it is difficult to measure it. It is also likely that the coloured areas will not be absolutely circular. ‘Mistakes’ should not be included as sources of error – these could include not measuring the temperature properly or not adding the same volume of liquid to each hole.

Common misunderstandings and misconceptions ◆

It is very common for students to think that the movement of particles in diffusion is somehow purposeful – that the particles try to move so that they end up evenly spaced.

Students may also think that cells somehow make substances diffuse. This misconception may become apparent through statements such as ‘The cell diffuses oxygen into itself ’. ◆ Students who do not have a clear grasp of particle theory may confuse diffusion with mass flow (although they will not know this term). It is very important that they think of diffusion in terms of individual particles each moving randomly.

Homework ideas ◆ ◆

Coursebook questions 3.1 to 3.3 Workbook exercise 3.1 Diffusion experiment

Topic 2

Osmosis

Coursebook section 3.2 Teaching ideas ◆

This lesson introduces osmosis. The crucial factor is to develop this from the students’ work on diffusion, because osmosis is simply a particular example of diffusion, not something totally different. There is also considerable opportunity here to help students to develop various skills, including taking measurements and recording results (make sure that all the values in the results table are recorded to the same number of decimal places), drawing a line graph, processing the results (calculating mean rate of movement), making predictions and planning an experiment. If all this is new to the students, you may need an extra lesson to cover it. ◆ Set up the apparatus shown in Activity 3.5 Measuring the rate of osmosis (but do not attempt to actually do the activity yet – this is simply a demonstration of osmosis at this stage). Many students will be able to use their understanding of what happened in Activity 3.2 to explain what they see happening here. If you allow them to work out for themselves what is happening, they will end up with a much firmer grasp of osmosis than

Original material © Cambridge University Press 2014 © Cambridge University Press 2014

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if they are simply presented with a description of it. Ensure that they understand that water molecules are moving in both directions through the membrane, not all from the water into the concentrated sugar solution. ◆ Through discussion, build up the formal definition of osmosis. Ensure that students do not become confused between the idea of a concentrated solution – that is, one in which there is a lot of solute – and a solution where there is a high concentration of water molecules – that is, a dilute solution. You may like to avoid this by using the term water potential (see below) instead. Note that the correct term to use for the membrane is ‘partially permeable’, not ‘selectively permeable’. ◆ If your students are studying the Supplement, this is a good time to introduce the idea of water potential. This should be dealt with very, very simply. Students only need to know that a solution with a lot of water in it has a high water potential, and that one with less water and more solute has a lower water potential. Most students have no difficulty with this concept. From their understanding of diffusion, they should be able to predict that there will be net diffusion of water molecules from the solution with a higher water potential to the solution with a lower water potential. ◆ Once you are happy that the class has a good basic understanding of osmosis, you can begin to look at how it affects living cells. Draw an animal cell on the board, and ask students to tell you where there is a partially permeable membrane. Then draw a piece of Visking tubing containing sugar solution. Draw a beaker around the cell and another around the Visking tubing, and draw water in each beaker. Ask students what is inside the cell, and draw out the idea that it is a fairly concentrated solution (there are many solutes, such as proteins, for example). Now ask them to tell you what will happen to the Visking tubing, and then what will happen to the cell. Most groups of students will be able to predict that water will move into the cell and into the Visking tubing by osmosis. ◆ Now replace the drawing of the Visking tubing with a drawing of a plant cell. Explain that water and solutes can all move freely through the cell wall – it is fully permeable. Again, students should be able to predict that water will move into the cell. Discuss the fact that the animal cell may burst and the plant cell will not, because of the strength of the cell wall. ◆ Work through a similar train of thought with the cells placed in a solution more concentrated than the cytoplasm. Students will almost certainly not be able to predict that the cell contents pull away from the cell wall in the plant cell, but if you tell them it happens they should be able to explain why. (Note that, in many types of cell, the membrane remains fixed to the wall at some points. It is when these points do eventually tear away that the cell is irreversibly damaged.) ◆ Activities 3.4, 3.5 and 3.6 could each be carried out.

Common misunderstandings and misconceptions ◆

The definition of osmosis frequently causes confusion between a ‘concentrated solution’ and a ‘high concentration of water molecules’. This can result in weaker students saying that ‘osmosis is the opposite of diffusion’. ◆ As for diffusion, confusion arises if students are not able to visualise the water molecules and solute molecules as separate entities. ◆ Students often confuse the cell wall and cell membrane. ◆ Students may say that plant cells do not burst when placed in pure water because the cell wall prevents the water from going in.

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Homework ideas ◆ ◆ ◆

Coursebook questions 3.4 to 3.15 End-of-chapter questions 1, 2 and 3 Workbook exercise 3.2 How plants take up water ◆ Workbook exercise 3.3 Osmosis and potatoes ◆ Worksheet 3.1 Drying mangoes

Topic 3 Active transport Coursebook section 3.3 Teaching ideas ◆

Discuss the ideas on page 35 in the Coursebook. Build up the formal definition with the class. ◆ Ask students to do Workbook exercise 3.4 Diffusion and active transport. It may be useful for them to work in groups, so they can discuss their ideas within the group. When all have finished, ask one person in a group to tell you their suggested answers to a question, gradually working your way through all of them.

Common misunderstandings and misconceptions ◆

More able students will be able to understand this concept, but it does require the ability to visualise very small particles, and to appreciate how energy is required to move particles against their concentration gradient.

Homework ideas ◆ ◆ ◆

End-of-chapter question 5 Workbook exercise 3.4 Diffusion and active transport Worksheet 3.2 Diffusion, osmosis and active transport

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Teaching ideas Chapter 4 The chemicals of life Syllabus section covered: 4

Teaching resources Syllabus section

Topic

40-minute periods

Resources in Coursebook

Resources in Workbook

Resources on this CD-ROM

4

Water

2 to 4

Questions 4.1 to 4.6

Exercise 4.1 Carbohydrates

Worksheet 4.1 Carbohydrates

EOCQs 1, 3

Carbohydrates

Activity 4.1 Testing foods for sugars Activity 4.2 Testing foods for starch 4

Fats

2 to 3

Questions 4.7 to 4.9

Worksheet 4.2 Using lipids (fats and oils)

Activity 4.3 Testing foods for fats 4

Proteins

2 to 5

Questions 4.10 to 4.14 EOCQs 2, 4 Activity 4.4 Testing foods for protein

4

DNA

1 to 2

EOCQ 5

Exercise 4.2 Proteins

Worksheet 4.3 Body composition

Exercise 4.3 Testing a hypothesis Exercise 4.4 DNA

Topic 1 Water; Carbohydrates Coursebook sections 4.1 and 4.2 Teaching ideas ◆

Ask students for suggestions about how much of their body consists of water. (It is a little below 70%.) Ask them why we need water. You are likely to get the answer ‘so we don’t get dehydrated’, so you will need to move the thinking on by asking what happens when we get dehydrated, which can then lead towards ideas about what water actually does in the body.

This may be a good time to introduce the term ‘metabolism’. ◆ Show students a plate of different foods and ask them which ones contain carbohydrates. This can lead into a discussion of what carbohydrates are. You could use popper beads to illustrate how sugar molecules link together to form disaccharides and polysaccharides. Show them how sugar dissolves in water but starch does not. (The starch that is often used in biology experiments may be ‘soluble’ starch, but still does not easily dissolve in cold water.) Students will probably be able to tell you that carbohydrates are energy foods. You could show them Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 4: Teaching ideas

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video clips or photographs (there are plenty on the Internet) of athletes in a long-distance race, or tennis players, drinking fluids containing carbohydrates, and ask them why they do this. ◆ Do Activity 4.1 Testing foods for sugars, and Activity 4.2 Testing foods for starch.

Depending on the previous experience of the class, and their confidence in a practical situation, you could run these two activities together, so that they test each of the foods for both reducing sugars and for starch. This is a good opportunity to develop the skills of careful observation and recording of results. Ensure that they do not write ‘no change’ in the ‘colour’ column, but state the colour that they see.

Common misunderstandings and misconceptions ◆

This is usually a straightforward topic, with no difficult concepts – so long as students are able to use the term ‘molecule’ with confidence.

Homework ideas ◆ ◆ ◆ ◆

Workbook exercise 4.1 Carbohydrates Coursebook questions 4.1 to 4.6 Worksheet 4.1 Carbohydrates End-of-chapter questions 1, 3

Topic 2

Fats

Coursebook section 4.3 Teaching ideas ◆

For continuity from the previous lesson, you could show students the same plate of foods and now ask which ones contain fats. ◆ Discuss the need for fats in living organisms. Tell students that fats contain twice as much energy per gram as carbohydrates. You could discuss the relatively high fat content of the diet of Inuit people, or others who live in cold climates, and perhaps also investigate the diets of people carrying out strenuous activities in polar regions, such as polar explorers.

Ensure that students also think about the uses of fats in plants; you could show them bottles of various cooking oils (groundnut, olive, corn and so on) and draw out the idea that these all come from plant seeds, and why seeds often contain oils. (Oils are fats that are liquid at room temperature.) ◆ Do Activity 4.3 Testing foods for fats. You may prefer to do this as a demonstration, as it works best with absolute ethanol rather than a solution of it, but in that case do try to involve the students in the tests and ensure that they each write down the results.

Common misunderstandings and misconceptions ◆

Many students will think that ‘fats are bad for you’, so it is important to emphasise their positive roles in the body as well as mentioning why too much high-fat food in the diet may be bad for health. This latter point is dealt with more fully later in the course.

Homework ideas ◆

Produce a poster defending the reputation of fats – that is, emphasising why we need them in the diet. ◆ Coursebook questions 4.7 to 4.9 ◆ Worksheet 4.2 Using lipids (fats and oils) Original material © Cambridge University Press 2014 © Cambridge University Press 2014

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Topic 3

Proteins

Coursebook section 4.4 Teaching ideas ◆

As for carbohydrates and fats, students should be able to tell you examples of foods that contain protein. Students will probably be able to tell you that proteins are needed for ‘growth and repair’, but they should now be introduced to some particular examples of proteins – for example, haemoglobin, enzymes, antibodies or insulin. ◆ Do Activity 4.4 Testing foods for protein. It is a good idea to set up a tube showing the colour obtained when there is no protein present, and another showing the purple colour, for reference. ◆ Workbook exercise 4.3 Testing a hypothesis, could be done as a class exercise. Students could then carry out their plans.

Common misunderstandings and misconceptions ◆

There are usually no difficulties with this topic.

Homework ideas ◆ ◆ ◆ ◆ ◆

Workbook exercise 4.2 Proteins Workbook exercise 4.3 Testing a hypothesis Worksheet 4.3 Body composition Coursebook questions 4.10 to 4.14 End-of-chapter questions 2, 4

Topic 4

DNA

Coursebook section 4.5 Teaching ideas ◆

If at all possible, show learners a model of part of a DNA molecule. They do not need to know the detailed structure, but should understand that each strand is made up of a series of bases, and that complementary bases pair up with each other. ◆ End-of-chapter question 5 is a good test of understanding of the structure of DNA. This could be discussed as a class or group exercise.

Common misunderstandings and misconceptions ◆

There are usually no difficulties with this topic, as long as no attempt is made to teach too much detail. The way in which DNA codes for the assembly of amino acids into proteins is dealt with in Chapter 18.

Homework ideas ◆

Workbook exercise 4.4 DNA

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Teaching ideas Chapter 5

Enzymes

Syllabus section covered: 5

Teaching resources Syllabus section

Topic

40-minute periods

Resources in Coursebook

5

Biological catalysts

1

Questions 5.1 to 5.6

5

Properties of enzymes

3 to 8

Activity 5.1 The effect of catalase on hydrogen peroxide

Exercise 5.1 Writing enzyme questions

Questions 5.7 to 5.9

Exercise 5.2 Lipase experiment

EOCQs 1, 2, 3, 4 Activity 5.2 Investigating the effect of pH on the activity of catalase Activity 5.3 Investigating the effect of temperature on the activity of amylase

Resources in Workbook

Resources on this CD-ROM Worksheet 5.1 Enzyme facts Worksheet 5.2 Catalase

Exercise 5.3 Finding the optimum pH for amylase Exercise 5.4 How enzymes work

Activity 5.4 Investigating the effect of temperature on the activity of catalase

Topic 1

Biological catalysts

Coursebook section 5.1 Teaching ideas Note that this chapter provides ideal opportunities for students to work intensively on building their practical skills. There are many practical activities in the Coursebook, and exercises in the Workbook and worksheets. The sequence suggested below is just one of many possibilities.

You may like to use all of the material provided or select just some of it, depending on the time available. ◆

Consider beginning almost straight away with Activity 5.1 The effect of catalase on hydrogen peroxide. Students always enjoy this, and you could use it to get their attention and interest for a discussion covering the properties of enzymes. It is a simple experiment Original material © Cambridge University Press 2014

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for students to do, making a good starting point for the more demanding practical activities coming up in the next few lessons. ◆ Following Activity 5.1, discuss what enzymes are and how they work. ◆ Students could make models of enzymes and substrates, making the substrate a complementary shape to the enzyme.

Common misunderstandings and misconceptions ◆

Students often appear to believe that enzymes are alive. This leads to statements like ‘high temperatures kill enzymes’. Try to deal with this misconception very early on.

Homework ideas ◆ ◆

Questions 5.1 to 5.6 Worksheet 5.1 Enzyme facts

Topic 2

Properties of enzymes

Coursebook section 5.2 Teaching ideas ◆

Activity 5.2 Investigating the effect of pH on the activity of catalase follows smoothly on from Activity 5.1, as it involves the same enzyme. However, the technique involved is very different and the level of difficulty for the students is much greater, involving more complex manipulation, measurement and the collection and display of quantitative results. At this relatively early point in the course, an outline results table is provided. The questions ask students to address the reliability of their data and to think about important sources of experimental error. They are likely to need help with this at this stage, especially in distinguishing between sources of experimental error and ‘mistakes’ they may have made.

This technique has several very significant sources of error, which should make it possible for most students to be able to recognise them. ◆ Students could do Activity 5.3 Investigating the effect of temperature on the activity of amylase. This gives them an opportunity to work with a different enzyme, and a different method of measuring the rate of activity. The extra step of having to test for the disappearance of the substrate using iodine solution is often confusing to students, who lose track of what is actually happening inside the test tubes. ◆ Set groups the task of planning the experiment in Activity 5.4 Investigating the effect of temperature on the activity of catalase. The task is made easier because they will be using an enzyme they have used before. They could measure the rate of reaction as in Activity 5.2 or they could measure the height of the froth produced after a set time. When they have put together their main ideas, ask someone from each group to report back to the class, and discuss the various plans. Encourage them to focus clearly on the variables they will change, keep the same and measure. They could use the self-assessment checklist for planning in the Workbook and also on the student CD-ROM. ◆ Workbook exercise 5.2 Lipase experiment, is another opportunity to develop planning skills; it could be done as a class or group exercise.

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Common misunderstandings and misconceptions ◆

As mentioned above, students frequently confuse experimental error and human mistakes.

The distinction will need reinforcing here, and again each time they discuss the results of their experiments in the future. ◆ Some students may think that a longer time (giving a larger number in their results table) represents a higher rate of reaction.

Homework ideas ◆ ◆ ◆ ◆ ◆ ◆

Coursebook questions 5.7 to 5.9 Workbook exercise 5.1 Writing enzyme questions Workbook exercise 5.2 Lipase experiment Workbook exercise 5.3 Finding the optimum pH for amylase Workbook exercise 5.4 How enzymes work Worksheet 5.2 Catalase

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Teaching ideas Chapter 6

Plant nutrition

Syllabus sections covered: 6.1, 6.2, 6.3

Teaching resources Syllabus section

Topic

40-minute periods

Resources in Coursebook

6.1

Types of nutrition; photosynthesis

1

Questions 6.1 to 6.3

6.2

Leaves

2 to 3

Questions 6.4 to 6.15 EOCQs 2, 4 Activity 6.1 Use a microscope to observe the cells that cover a leaf

6.1, 6.3

Products of photosynthesis

2 to 4

Resources in Workbook

Resources on this CD-ROM Worksheet 6.1 The photosynthesis equation

Exercise 6.1 How a palisade cell obtains its requirements

Worksheet 6.2 Leaves as food and shelter

Exercise 6.2 Sun and shade leaves

Questions 6.16 to 6.19 EOCQs 1, 3, 5, 6, 7 Activity 6.2 Testing a leaf for starch Activity 6.5 To show that oxygen is produced in photosynthesis

6.1

Factors affecting photosynthesis

2 to 6

Questions 6.20 to 6.22 EOCQ 8 Activity 6.3 To see if light is needed for photosynthesis Activity 6.4 To see if chlorophyll is needed for photosynthesis

Exercise 6.3 Limiting factors Exercise 6.4 Effect of increased carbon dioxide and temperature on tree growth

Activity 6.6 To see if carbon dioxide is needed for photosynthesis Activity 6.7 Photosynthesis in a pond weed Activity 6.8 Investigating the effect of light intensity on photosynthesis (continued)

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Syllabus section

40-minute periods

Topic

Resources in Coursebook

Resources in Workbook

Resources on this CD-ROM

Activity 6.9 Investigating the effect of carbon dioxide concentration on the rate of photosynthesis Activity 6.10 Investigating the effect of temperature on the rate of photosynthesis

Topic 1 Types of nutrition; photosynthesis Coursebook sections 6.1, 6.2 Teaching ideas This chapter, like Chapter 5, provides ideal opportunities for students to work intensively on building their practical skills. There are many practical activities in the Coursebook, and exercises in the Workbook and worksheets. ◆

Most students are likely to know something about photosynthesis, so you could ask them to tell you what plants use and what they make, and what the energy source is. You can then build up the word equation. It is good to have some plants visible, either in the room or outside – encourage students to look at them and to tell you why they are green. ◆ Students following the Supplement also need to know the balanced equation. You could use Worksheet 6.1 The photosynthesis equation, at this point.

Common misunderstandings and misconceptions ◆

Students often write that ‘photosynthesis is the way that plants respire’.

Homework ideas ◆ ◆

Coursebook questions 6.1 to 6.3 Worksheet 6.1 The photosynthesis equation

Topic 2

Leaves

Coursebook section 6.3 Teaching ideas ◆

Leaf structure is easy for students to study and understand. You could give students two very different leaves (e.g. from a monocot and dicot) and ask them to make drawings of them, calculate magnification, and produce a table comparing their structures. ◆ Activity 6.1 Use a microscope to observe the cells that cover a leaf, makes a good introduction to the internal, microscopic structure of a leaf – students learn that there are little holes in the lower epidermis, and can then find out where they lead to. ◆ Introduce diagrams or photographs of the internal structure of leaves. Scanning electronmicrographs, such as Figure 6.4 in the Coursebook, are a good starting point, as they show the structures in three dimensions, which may be easier for some students to relate to reality than diagrams such as Figure 6.3. Show students a whole leaf, cut or tear it in half and explain that they are looking at the very thin edge.

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◆

You could provide a sheet of paper with drawings of individual cells from each of the layers, which students can cut out and paste onto a sheet of paper to build up a ‘diagram’ of a transverse section through a leaf. ◆ Once the structure of the leaf has been covered, you can ask students to suggest how water, light and carbon dioxide get to a chloroplast inside a palisade cell (which is where most photosynthesis takes place). If you have a model showing leaf structure, this can be very helpful.

Common misunderstandings and misconceptions ◆

Students often do not appreciate what diagrams of a transverse section of a leaf represent, because they cannot imagine that something as thin as a leaf can contain so many layers of cells. ◆ Students often think that water enters leaves through the stomata. ◆ They may think that leaves (particularly the stomata) do something active to bring carbon dioxide into the leaf. ◆ Students say that chlorophyll ‘attracts’ sunlight, rather than absorbs energy from it. ◆ They tend to confuse chlorophyll with chloroplasts.

Homework ideas ◆ ◆ ◆ ◆ ◆

Coursebook questions 6.4 to 6.15 End-of-chapter questions 2, 4 Workbook exercise 6.1 How a palisade cell obtains its requirements Workbook exercise 6.2 Sun and shade leaves Worksheet 6.2 Leaves as food and shelter

Topic 3

Products of photosynthesis

Coursebook section 6.4, 6.5 Teaching ideas ◆

You could begin this topic by asking students what plants make in photosynthesis, working towards the idea that a leaf will contain starch. Ask them to tell you how to test for starch, and then drop some iodine solution onto the leaf. Ask the students why the leaf does not go blue-black. Use discussion to draw out the idea that the starch is inside the chloroplasts in the palisade cells, and that the iodine solution cannot get through the partially permeable cell membranes to reach it. This can lead to a demonstration of how to test a leaf for starch, as described in Activity 6.2 Testing a leaf for starch. ◆ Activity 6.5 To show that oxygen is produced in photosynthesis provides students with first-hand experience of the production of oxygen. Depending on the temperature and light intensity in the laboratory, you may be able to obtain results quite quickly, but may need to leave the collection of results until the next lesson. ◆ Alternatively, Activity 6.7 Photosynthesis in a pond weed involves the collection of quantitative results. ◆ A good follow-up to these practical activities could be the discussion of the other products of photosynthesis, which are covered in Section 6.4 in the Coursebook. This is also a good time to deal with the need for magnesium ions and nitrate ions.

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Common misunderstandings and misconceptions ◆

Students often do not appreciate what diagrams of a transverse section of a leaf represent, because they cannot imagine that something as thin as a leaf can contain so many layers of cells. ◆ Students often think that water enters leaves through the stomata. ◆ They may think that leaves (particularly stomata) do something active to bring carbon dioxide into the leaf. ◆ Students often say that chlorophyll ‘attracts’ sunlight, rather than absorbs energy from it. ◆ They tend to confuse chlorophyll with chloroplasts.

Homework ideas ◆ ◆

Coursebook questions 6.16 to 6.19 End-of-chapter questions 1, 3, 5, 6, 7

Topic 4

Factors affecting photosynthesis

Coursebook section 6.5, 6.6, 6.7 Teaching ideas ◆

There are numerous Activities that could be done at this point. Activity 6.3, To see if light is needed for photosynthesis, Activity 6.4, To see if chlorophyll is needed for photosynthesis could be done by students. Activity 6.6, To see if carbon dioxide is needed for photosynthesis, would be best done as a demonstration. ◆ Activity 6.8, Investigating the effect of light intensity on photosynthesis, is a planning exercise. This is an excellent task for helping students to develop their scientific enquiry skills. It is also a good introduction to the concept of limiting factors. ◆ Activity 6.9, Investigating the effect of carbon dioxide concentration on the rate of photosynthesis, also involves limiting factors. ◆ Activity 6.10, Investigating the effect of temperature on the rate of photosynthesis, is another planning exercise. ◆ The importance of photosynthesis to other living organisms can be discussed. This can be revisited later, when respiration is discussed. Alternatively, you might like to carry out the experiment described in Workbook exercise 11.2 The effect of animals and plants on the carbon dioxide concentration in water, at this point.

Common misunderstandings and misconceptions ◆

Students often have difficulty in understanding that, when a graph such as that in Figure 6.13 levels off, something other than the factor on the y-axis is limiting the rate of photosynthesis.

Homework ideas ◆ ◆ ◆ ◆

Coursebook questions 6.20 to 6.22 End-of-chapter question 8 Workbook exercise 6.3 Limiting factors Workbook exercise 6.4 Effect of increased carbon dioxide and temperature on tree growth

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Teaching ideas Chapter 7 Animal nutrition Syllabus sections covered: 7.1, 7.2, 7.3, 7.4, 7.5

Teaching resources Syllabus section

Topic

40-minute periods

Resources in Coursebook

Resources in Workbook

Resources on this CD-ROM

7.1

Diet

2 to 4

Questions 7.1 to 7.6

Exercise 7.1 Diet

Worksheet 7.1 Essential amino acids

Exercise 7.2 Functions of the digestive system

Worksheet 7.2 Checking your teeth

Exercise 7.3 Tooth decay data analysis

Worksheet 7.3 The structure of the digestive system

EOCQs 2, 5, 7 Activity 7.1 Testing foods for vitamin C 7.2, 7.3, 7.4, 7.5

Digestion, absorption and assimilation

3 to 7

Questions 7.7 to 7.10 Questions 7.11 to 7.14 EOCQ 6 Activity 7.2 Checking your teeth Questions 7.15 to 7.23 EOCQs 1, 3, 4

Exercise 7.5 Vitamin D absorption

Worksheet 7.4 Digestion vocabulary

Activity 7.3 A model of absorption 7.2

Cholera and diarrhoea

Topic 1

Diet

1

Questions 7.24 and 7.25

Exercise 7.4 Cholera patterns in Bangladesh

Coursebook section 7.1 Teaching ideas ◆

Use a quick quiz to find out what students already know about diet. There can sometimes be difficulties if they feel they ‘know it all already’. It is almost certain that their knowledge will not be sufficient for IGCSE level. If you give them a 10-mark multiple-choice test at the start of the lesson, and then again at the end, this is likely to show them that they have learnt something new during this lesson. ◆ If possible, use an interactive computer program that allows students to input the food they have eaten during the day and be provided with a breakdown of its energy content and nutrient content. They can compare results, and discuss bad and good points about each other’s diets. (This can be done using food tables – like the highly pared-down example on page 75 of the Coursebook – but this is very laborious and time-consuming, and students do not usually enjoy doing it.)

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◆

Take the opportunity to ask students to think back to what they learnt about proteins, fats and carbohydrates in Chapter 4 The chemicals of life. ◆ You could ask students to bring in some food labels and use some of these to discuss with the class the nutrient contents of various foods. ◆ Activity 7.1 Testing foods for vitamin C, could be carried out. Once students have experience of the test, they can then plan and carry out an investigation as suggested in the instructions.

Common misunderstandings and misconceptions ◆ ◆

Students may associate the term ‘diet’ with trying to lose weight.

They may think that fats are entirely bad and not appreciate that they are essential nutrients. ◆ It is very common for students to think that one nutrient can ‘contain’ another – for example, they may say that vitamins supply you with protein.

Homework ideas ◆ ◆ ◆

Coursebook questions 7.1 to 7.6 End-of-chapter questions 2, 5, 7 Make an illustrated leaflet about balanced diets (either one page in detail, or an outline plan for the whole leaflet) that could be placed in a doctor’s waiting room for patients to read. ◆ Worksheet 7.1 Essential amino acids ◆ Workbook exercise 7.1 Diet

Topic 2

Digestion, absorption and assimilation

Coursebook sections 7.2, 7.3, 7.4, 7.5 Teaching ideas This is, in reality, a large collection of topics. There are many different possible routes through, and which you choose will depend to a large extent to the previous experience and knowledge of your students. It is well worth using some kind of assessment to find out what they already know and understand before you begin these topics. It is very easy for them to ‘switch off ’ because they have covered it all before. If they have indeed covered much of this before, then it is important to try to ensure that everything you do has something new, fresh and challenging in it, to keep their interest. ◆

Digestion and the need for it is frequently completely misunderstood by students taking IGCSE examinations. A clear understanding of what digestion is, and why it is necessary, is fundamental to an understanding of the whole of the rest of this topic, so it is well worth taking time over. For example, you could use a cylindrical piece of modelling clay with a hole through its centre to show students how the digestive system is a tube that runs from one end of the body to the other, and that its contents are still in the ‘outside world’ and not actually inside the body. This is a difficult concept for many students but unless they understand it, digestion and absorption make no sense at all. You could also do something similar with a tube made from a piece of wire netting or other perforated material. Feed strings of popper beads inside the tube, and show how they need to be split apart into individual beads before they can get through the holes in the sides of the tube.

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◆

Follow this up with a discussion of how only small molecules can get through the wall of the alimentary canal and enter the body tissues. This can lead in to the ideas of mechanical and chemical digestion. Figure 7.10 looks very daunting, but you may like to work through this slowly with students, showing them how first mechanical digestion and then chemical digestion produce small molecules of nutrients that can get through the wall of the intestine. ◆ Teeth make a much easier topic for most students to deal with, and indeed many may already have covered this material in earlier years. Students usually enjoy looking at their own teeth, so you could begin the lesson with Worksheet 7.2 Checking your teeth.

However, this involves eating, so it may be better not to do this in a laboratory. ◆ You may have some human teeth that students can look at, alongside Figures 7.12 and 7.13. It is worth collecting some milk teeth and, if possible, sawing some of them in half so that their internal structure can be seen. Dental X-rays are another potential source of information, if you can obtain any. ◆ If available, use a three-dimensional model of the human body to show students the different regions of the alimentary canal and their positions in the body. ◆ You may like to dissect a small mammal to show the alimentary canal, liver and pancreas. ◆ Use Worksheet 7.3 The structure of the digestive system to help students to learn the positions and names of the organs in the digestive system. ◆ Use a piece of rubber tubing and a marble to illustrate how muscles squeezing inwards cause a bolus of food to move through the alimentary canal. ◆ A piece of velvet or pile carpet can give students a good picture of how the villi in the small intestine increase surface area. ◆ Activity 7.3 A model of absorption, could be carried out.

Common misunderstandings and misconceptions ◆

It is very common for students to have difficulty with the concepts of digestion and absorption. They fail to understand that molecules need to move from inside the alimentary canal, through its walls, and into the blood (or lymph) before they can considered to be truly inside the body. ◆ They may confuse ingestion with indigestion. ◆ It is very common for students to fail to understand that the alimentary canal is a closed tube which runs, uninterrupted, from mouth to anus. They may think that food goes through the pancreas and liver, or even directly to the kidneys. This misunderstanding can lead to students making statements about the kidneys ‘excreting liquids from the foods that we eat’. ◆ Some old textbooks describe enzymes being present in ‘intestinal juice’ in the small intestine, but this is not correct. The enzymes in the small intestine come either from pancreatic juice or from the cells covering the villi. ◆ Many textbooks imply that water is absorbed only in the colon. Most absorption of water takes place in the small intestine, with only a relatively small quantity being absorbed in the colon.

Homework ideas ◆ ◆ ◆ ◆

Coursebook questions 7.7 to 7.23 End-of-chapter questions 1, 3, 4, 6 Workbook exercise 7.2 Functions of the digestive system Workbook exercise 7.3 Tooth decay data analysis Original material © Cambridge University Press 2014

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◆ ◆ ◆ ◆

Workbook exercise 7.5 Vitamin D absorption Worksheet 7.2 Checking your teeth Worksheet 7.3 The structure of the digestive system Worksheet 7.4 Digestion vocabulary

Topic 3

Cholera and diarrhoea

Coursebook section 7.4 Teaching ideas ◆

You could begin this section with a news report about a recent outbreak or epidemic of cholera, and discuss with the students how it is caused by a bacterium, and the conditions in which the disease is most likely to spread. ◆ Work through Figure 7.25 with students, explaining how cholera causes diarrhoea. Links should be made with earlier work on osmosis.

Common misunderstandings and misconceptions ◆

There are no common problems with this topic.

Homework ideas ◆ ◆

Coursebook questions 7.24 and 7.25 Workbook exercise 7.4 Cholera patterns in Bangladesh

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Teaching ideas Chapter 8 Transport in plants Syllabus sections covered: 8.1, 8.2, 8.3, 8.4

Teaching resources Syllabus section 8.1

Topic Plant transport systems

40-minute periods

Resources in Coursebook

2

Activity 8.1 Identify the positions of xylem vessels in roots, stems and leaves

Resources in Workbook

Resources on this CD-ROM

Questions 8.1 to 8.5 EOCQ 4 8.2

Water uptake

2

Activity 8.2 To see which part of a stem transports water and solutes

Worksheet 8.1 The pathway of water movement through a plant

Questions 8.6 and 8.7 EOCQ 6 8.3

Transpiration

2 to 4

Activity 8.3 To see which surface of a leaf loses most water

Exercise 8.1 A transpiration experiment

Activity 8.4 To measure the rate of transpiration of a potted plant

Exercise 8.2 Tissues in a root

Worksheet 8.2 The mechanism of water movement through a plant

Activity 8.5 Using a potometer to comapre rates of transpiration under different conditions Questions 8.8 to 8.11 EOCQs 1, 3 8.4

Transport of manufactured food

2

EOCQs 2, 5

Exercise 8.3 Sources and sinks

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

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Topic 1

Plant transport systems

Coursebook section 8.1 Teaching ideas ◆

You could begin the lesson with Activity 8.1 Identify the positions of xylem vessels in roots, stems and leaves. ◆ Activity 8.2 To see which part of a stem transports water and solutes could also be carried out at this point. Students can relate what they see to the structures shown in Figure 8.7, and discuss the positions of xylem in the stem and in roots. Students will probably know the terms ‘xylem’, ‘phloem’ and ‘vascular bundle’ from their earlier work on leaves. ◆ If students are working at wooden desks, they will probably be able to see xylem vessels in section. ◆ Micrographs and Figures 8.6 and 8.7 can be used to identify the positions of phloem.

Common misunderstandings and misconceptions ◆

Students may find it difficult to visualise the three-dimensional arrangement of xylem vessels from looking at a transverse section, and may therefore not appreciate that continuous vessels run from the roots all the way up the stem and into the leaves.

Homework ideas ◆ ◆

Coursebook questions 8.1 to 8.5 End-of-chapter question 4

Topic 2 Water uptake Coursebook section 8.2 Teaching ideas ◆

Show students bean or other seedlings with root hairs – these are usually clearly visible if the seeds are germinated in damp filter paper. Ask them what they think the root hairs do and discuss the very large surface area they provide. ◆ Draw a diagram of a root hair cell on the board. Ask students to think back to what they know about osmosis and to suggest how water gets inside a root hair cell. ◆ Use Figure 8.10 in the Coursebook to discuss how water moves from the outside of a root to the centre and into the xylem vessels. Use Figure 8.11 to introduce the idea of the transpiration stream.

Common misunderstandings and misconceptions ◆

Students often do not realise that water has to move horizontally from the outside of the root into its centre, before it can enter a xylem vessel.

Homework ideas ◆ ◆ ◆

Coursebook questions 8.6 and 8.7 End-of-chapter question 6 Worksheet 8.1 The pathway of water movement through a plant

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Topic 3 Transpiration Coursebook section 8.3 Teaching ideas ◆

Transpiration is the driving force for the movement of water up a plant. This is a crucial point for students to understand. Transpiration reduces hydrostatic pressure at the top of xylem vessels, so that water flows up them from higher pressure regions at their base. Use Figure 8.11 to introduce the idea of the transpiration stream. ◆ Students could do Activity 8.3 To see which surface of a leaf loses most water. They will need to think back to what they know about the structure of leaves, and remember where the stomata are situated. ◆ Students could set up Activity 8.4 To measure the rate of transpiration of a potted plant.

This will need to be revisited at regular intervals over the next few days. ◆ Activity 8.5 involves a potometer, but if you do not have one, it is easy to do this experiment using a long glass tube, as described in the Notes.

Common misunderstandings and misconceptions ◆

It is extremely common for students to fail to understand what makes water move up a plant. They may have no idea at all, or they may think that it moves up by osmosis. ◆ Students often think that water is lost from leaves as a liquid, and fail to understand that it evaporates from wet cell walls and then diffuses out through the stomata. ◆ Students may think that a large proportion of the water taken up is used in photosynthesis.

In fact, only a tiny proportion is used for this; almost all of it is lost by transpiration through the leaves.

Homework ideas ◆ ◆ ◆ ◆ ◆

Coursebook questions 8.8 to 8.11 End-of-chapter questions 1 and 3 Workbook exercise 8.1 A transpiration experiment Workbook exercise 8.2 Tissues in a root Workheet 8.2 The mechanism of water movement through a plant

Topic 4 Transport of manufactured food Coursebook section 8.4 Teaching ideas ◆

Remind students of the positions of xylem and phloem in roots, stems and leaves, and ask them to tell you what is transported in phloem. ◆ Show students plants in various stages of growth – for example, a recently germinated seed, an adult growing plant with green leaves, a potato tuber beginning to sprout. Ask them to suggest where the main source of ‘food’ for the plant is made or stored. Introduce the word ‘source’. Then ask which parts of the plant need most ‘food’ – students should be able to suggest the regions that are growing. Introduce the word ‘sink’. ◆ Discuss the fact that materials can be transported both up and down the plant in phloem (and in different directions at different stages of growth), in contrast to xylem in which transport is always from roots to stem.

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Common misunderstandings and misconceptions ◆ ◆

Students often think that glucose, not sucrose, is transported in phloem.

They may not appreciate that the two transport systems in a plant (xylem and phloem) are separate from one another. ◆ They may find difficulty with the concept of different parts of a plant changing their roles from sources to sinks at different times of year. Even those who do begin to grasp this idea may make the mistake of saying that leaves send sucrose to roots ‘in the winter’ (because they appreciate that roots need nutrients then), rather than in the summer, in preparation for winter.

Homework ideas ◆ ◆

End-of-chapter questions 2 and 5 Workbook exercise 8.3 Sources and sinks

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Teaching ideas Chapter 9 Transport in animals Syllabus sections covered: 9.1, 9.2, 9.3, 9.4

Teaching resources Syllabus section

Topic

40-minute periods

Resources in Coursebook

Resources in Workbook

Resources on this CD-ROM

Exercise 9.3 Double and single circulatory systems

9.1

Circulatory systems

1

9.2

The heart

3 to 5

Activity 9.1 Dissecting a heart Questions 9.1 to 9.12 to 9.19 EOCQ 7 Activity 9.2 To find the effect of exercise on the rate of heart beat

Exercise 9.1 Risk of heart attack

Worksheet 9.1 Heart beat

Exercise 9.2 The heart in a fetus

Questions 9.13 to 9.19 EOCQ 6 9.3

Blood vessels

2

Questions 9.20 to 9.26

Worksheet 9.2 Blood vessels

EOCQs 1, 4 9.4

Blood

2

Questions 9.27 to 9.35 EOCQs 2, 3, 5

9.3, 9.4

Lymph and tissue fluid

1

Exercise 9.4 Changes in the blood system at high altitude

Questions 9.36 to 9.41

Worksheet 9.3 Blood, tissue fluid and lymph Worksheet 9.4 Comparing blood plasma, tissue fluid and lymph

Topic 1

Circulatory systems

Coursebook section 9.1 Teaching ideas ◆

Look at Figure 9.2 in the Coursebook with students, and discuss the pathway taken by the blood through the heart and to the lungs and the rest of the body. Discuss the meaning of the term ‘double circulation’. Compare this with the single circulation shown in Figure 9.3.

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Chapter 9: Teaching ideas

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Workbook exercise 9.3 Double and single circulatory systems is a good test of how well students have understood this concept.

Common misunderstandings and misconceptions ◆

Students often do not appreciate that the blood has to go all the way round the body in order to get from one side of the heart to the other.

Homework ideas ◆

Workbook exercise 9.3 Double and single circulatory systems

Topic 2 The heart Coursebook section 9.2 Teaching ideas ◆

If you and your students would enjoy it, a dissection of a heart would be very worthwhile at this point. You could do this as a demonstration, or provide sheep hearts for groups of students to dissect themselves, using Activity 9.1 Dissecting a heart. If this is not possible, use a three-dimensional model of a heart to demonstrate its structure. ◆ Students could listen to each other’s hearts, with a stethoscope if you have one, or with an ear placed to the chest of a friend. As a class, talk about what they can hear, and lead into a discussion of what happens during one heart beat, using Figure 9.11 in the Coursebook for reference. ◆ Students can do Activity 9.2 To find the effect of exercise on the rate of heart beat. ◆ Discuss the role of the coronary arteries in supplying oxygenated blood to the heart muscle. Ask students if they know what they should do to maintain a healthy heart. (Take care: some may have parents or other relatives who have died from a heart attack, so be sensitive.) Build up a list of ‘do’s and don’ts’.

Common misunderstandings and misconceptions ◆

Students often fail to appreciate the role of the heart muscle in contracting and therefore squeezing the blood in the heart, raising its pressure and pushing it out into the arteries. ◆ They may think that the two sides of the heart beat in succession, rather than in unison. ◆ It is very common for students to think that the valves in the heart open and close actively, rather than being pushed open or closed by the pressure of the blood. ◆ Students may not fully appreciate that heart muscle needs a constant supply of oxygen (brought by the coronary arteries) in order to respire, providing energy so that the muscle can contract. This is fundamental to a proper understanding of coronary heart disease.

Homework ideas ◆ ◆ ◆

Coursebook questions 9.1 to 9.19 End-of-chapter question 6 and 7 Workbook exercise 9.1 Risk of heart attack ◆ Workbook exercise 9.2 The heart in a fetus ◆ Worksheet 9.1 Heart beat

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Topic 3

Blood vessels

Coursebook section 9.3 Teaching ideas ◆

Show students micrographs of transverse sections of an artery and a vein. (You should be able to find suitable images on the Internet.) Ask them to tell you the differences they can see between them, and build up a comparison table on the board. Follow this with a discussion of the functions of arteries and veins. ◆ If students are studying the Supplement, ask them to suggest links between the structures and functions of arteries and veins. ◆ Discuss the structure and function of capillaries, emphasising their tiny size compared with arteries and veins. Show students micrographs of capillaries in tissues. ◆ Display a large image of a diagram such as that in Figure 9.17 or 9.18, and discuss the names of the vessels supplying the different organs. Using Figure 9.17, ask students to work out how blood could get from one point in the body to another – they can think of the circulatory system as being like a one-way traffic system in a town.

Common misunderstandings and misconceptions ◆

It is very common for students to think that arteries have to have thick walls because they are carrying oxygenated blood. They may think that oxygenated blood has a higher pressure than deoxygenated blood.

Homework ideas ◆ ◆ ◆

Coursebook questions 9.20 to 9.26 End-of-chapter questions 1, 2 and 4 Worksheet 9.2 Blood vessels

Topic 4

Blood

Coursebook section 9.4 Teaching ideas ◆

Ask students to look at blood vessels near the surface of the skin in their wrists or hands.

(These may not be visible in all students, depending on skin colour, so take care not to offend.) They should be able to see that the blood in the very thin-walled vessel looks blue. Tell them the vessels they are looking at are veins, and discuss why the blood looks blue, and why it looks red if they cut themselves (the haemoglobin quickly combines with oxygen in the air to become bright red oxyhaemoglobin). ◆ Show students slides or micrographs of blood films, and help them to pick out red cells, white cells, platelets and plasma. They may be surprised to find out that the only red part of blood is the red cells, and that plasma is straw-coloured. Note: it is now against health and safety regulations in most countries for students to observe their own fresh blood, or blood from another source. ◆ If suitable images can be found, ask students to make a list of the differences in appearance of red blood cells and white blood cells. ◆ Discuss the functions of red blood cells in oxygen transport, platelets in clotting, white cells in the immune response and plasma in the transport of dissolved substances and heat.

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Common misunderstandings and misconceptions ◆ ◆

It is very common for students to confuse red blood cells with haemoglobin.

Students may think that the large surface-area-to-volume ratio of red blood cells allows them to carry more oxygen. This is incorrect – a spherical cell would be able to carry more oxygen than a biconcave disc. The biconcave shape provides a large surface area to allow oxygen to diffuse into or out of the cell quickly. ◆ Students sometimes think that red blood cells transport glucose.

Homework ideas ◆ ◆ ◆

Coursebook questions 9.32 to 9.35 End-of-chapter question 5 Workbook exercise 9.4 Changes in the blood system at high altitude

Topic 5

Lymph and tissue fluid

Coursebook section 9.5 Teaching ideas ◆

Explain to students that capillaries have leaky walls, and discuss Figure 9.27 with them.

They will see the need for the leaked fluid to be returned to the blood system, and this can lead into a discussion of the lymphatic system. ◆ Show students photographs of a person who has oedema, and discuss how it is caused by a build up of tissue fluid that is not returned to the blood.

Common misunderstandings and misconceptions ◆

Students often find the concept of lymph difficult, as they cannot see lymphatic capillaries or lymph.

Homework ideas ◆ ◆ ◆ ◆

Coursebook questions 9.36 to 9.41 End-of-chapter question 2 Worksheet 9.3 Blood, tissue fluid and lymph Worksheet 9.4 Comparing blood plasma, tissue fluid and lymph

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IGCSE Biology

Chapter 9: Teaching ideas

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Teaching ideas Chapter 10

Pathogens and immunity

Syllabus section covered: 10

Teaching resources Syllabus section 10

Topic Pathogens; body defences

40-minute periods

Resources in Coursebook

Resources in Workbook

2

Questions 10.1 to 10.8

Exercise 10.1 Food poisoning in the USA

EOCQ 1

Resources on this CD-ROM

Exercise 10.2 Waste disposal in Australia 10

The immune system

3 to 5

Questions 10.9 to 10.11 EOCQs 2, 3, 4, 5

Exercise 10.3 Eradicating polio

Worksheet 10.1 The immune system Worksheet 10.2 Defence against disease

Topic 1

Pathogens: body defences

Coursebook sections 10.1, 10.2 Teaching ideas ◆

With the class, build up a list of about 20 diseases or illnesses on the board. Then ask students: which ones can be caught from someone else? Explain that these are called transmissible diseases, and that they are caused by microscopic organisms that can pass from one person to another. These organisms are called pathogens. You may also like to briefly explain the four main types of pathogen, which are listed in Table 10.1. ◆ Ask students to think of different ways in which pathogens might get inside the body.

Use their ideas to construct a simple classification of methods of entry, involving direct and indirect transmission. ◆ Now that students know how pathogens can get into the body, they can begin to think about how the body tries to prevent this from happening. Figure 10.5 summarises these methods. ◆ Good food hygiene is important in reducing disease transmission. You may be able to take students to visit the school kitchens, where someone might be able to give a talk about how they try to ensure that the food they supply does not contain pathogens or transmit illness.

Workbook exercise 10.1 Food poisoning in the USA, could be done at this point.

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 10: Teaching ideas

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Waste disposal is a big problem in all countries. You may be able to take students on a visit to a well-managed landfill site, where they can learn about how the site is constructed and maintained in order to reduce the change of diseases being transmitted. Sewage treatment can be mentioned here, but it is suggested that this is dealt with more fully later in the course (Chapter 22).

Common misunderstandings and misconceptions ◆

Students may confuse the vector of a disease (e.g. a mosquito) with the pathogen that causes it.

Homework ideas ◆ ◆ ◆ ◆

Coursebook questions 10.1 to 10.8 End-of-chapter question 1 Workbook exercise 10.1 Food poisoning in the USA Workbook exercise 10.2 Waste disposal in Australia

Topic 2 The immune system Coursebook section 10.3 Teaching ideas ◆

The immune system is extremely complex, and it is important to keep this topic quite simple at this stage. Students do not need to know about B cells and T cells. Explain how exposure to a particular pathogen elicits production of specific antibodies. Students may enjoy producing posters or short presentations to explain this process. ◆ The production of memory cells explains why we often become immune to a disease after having it once, and the same thing happens when vaccinations are given. You could show the students the vaccination schedule that is used in your country, and ask them if they remember having any vaccinations. If there is resistance to vaccination in your country, find news reports about this and discuss the reasons behind it. ◆ Explain to students how breast-feeding transfers antibodies to a baby, and ask them to suggest why this immunity does not last very long. They should be able to tell you that, without memory cells, immunity is only temporary. This can lead to a comparison of active and passive immunity. ◆ There are many different auto-immune diseases, and you will need to treat this topic carefully in case a family member of a student has such a disease.

Common misunderstandings and misconceptions ◆ ◆

Students frequently think that antibodies are cells.

They confuse antibodies, antigens and antibiotics.

Homework ideas ◆

Coursebook questions 10.9 to 10.11 ◆ End-of-chapter questions 2, 3, 4, 5 ◆ Workbook exercise 10.3 Eradicating polio ◆ Worksheet 10.1 The immune system ◆ Worksheet 10.2 Defence against disease Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 10: Teaching ideas

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Teaching ideas Chapter 11

Respiration and gas exchange

Syllabus sections covered: 11, 12.1, 12.2, 12.3

Teaching resources Syllabus section 12.1,12.2, 12.3

Topic Aerobic and anaerobic respiration

40-minute periods

Resources in Coursebook

Resources in Workbook

Resources on this CD-ROM

4 to 6

Activity 11.1 Investigating heat production by germinating peas

Exercise 11.1 Effect of temperature on the rate of respiration

Worksheet 11.1 Aerobic and anaerobic respiration

Activity 11.2 To show the uptake of oxygen during aerobic respiration

Exercise 11.2 The effect of animals and plants on the carbon dioxide concentration in water

Worksheet 11.2 Respiration equations

Activity 11.3 Investigating the production of carbon dioxide by anaerobic respiration Activity 11.4 Comparing the energy content of two kinds of food

Exercise 11.3 A simple respirometer

Questions 11.1 to 11.6 EOCQ 1 11

Gas exchange in humans

2 to 3

Activity 11.5 Examining lungs Questions 11.7 to 11.10

Exercise 11.4 Gas exchange surfaces in rats

EOCQs 2, 4 11

Breathing

2 to 4

Activity 11.6 Modelling how the diaphragm helps with breathing Activity 11.7 Gas exchange in small animals Activity 11.8 Comparing the carbon dioxide content of inspired and expired air Activity 11.9 Investigating the effect of exercise on rate and depth of breathing EOCQs 3, 5, 6 Original material © Cambridge University Press 2014

© Cambridge University Press 2014 IGCSE Biology

Chapter 11: Teaching ideas

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Topic 1 Aerobic and anaerobic respiration Coursebook section 11.1 Teaching ideas ◆

Ask students why living organisms need energy, encouraging them to think about individual cells as well as the whole organism. Build up a list similar to the one on page 141 in the Coursebook. ◆ Ask students where they get energy from, working towards the idea of respiration as the way in which energy is released from nutrient molecules (you could limit this to glucose) inside cells. You could use what they have learnt about combustion in chemistry as a comparison. ◆ Activity 11.1 Heat production in germinating peas, is a good illustration of the release of heat energy from living organisms. This is best done as a demonstration, and will need leaving for a day or so before results can be obtained. ◆ Activity 11.4 Comparing the energy content of two kinds of foods, involves measuring the energy released when food is burnt. This is a good illustration of how energy can be released from food by oxidation, and you could demonstrate the basic technique at this point, leaving the actual planning activity until later. ◆ Students will probably already be familiar with the equation for aerobic respiration, but the two types of anaerobic respiration may be less well known. When these have been explained, Worksheet 11.1 could be used to test how well students have understood these concepts. ◆ Activity 11.2 To show the uptake of oxygen during aerobic respiration uses a fairly simple respirometer to measure oxygen uptake, but this is still a difficult piece of apparatus to understand, and it is worth spending some time ensuring that students appreciate how it works before asking them to collect and interpret results. Workbook exercise 11.3 A simple respirometer, gives further practice. ◆ Activity 11.3 Investigating the production of carbon dioxide by anaerobic respiration may already have been done by students at an earlier stage. If so, then you could ask them to do question A6 instead of the basic activity.

Common misunderstandings and misconceptions ◆ ◆ ◆ ◆

Students often think that respiration uses energy.

They confuse digestion and respiration.

They do not appreciate that respiration takes place inside all living cells.

They confuse the two types of anaerobic respiration, thinking that both produce carbon dioxide.

Homework ideas ◆ ◆ ◆ ◆

Coursebook questions 11.1 to 11.6 End-of-chapter question 1 Workbook exercise 11.1 Effect of temperature on the rate of respiration Workbook exercise 11.2 The effect of animals and plants on the carbon dioxide concentration in water ◆ Workbook exercise 11.3 A simple respirometer ◆ Worksheet 11.1 Aerobic and anaerobic respiration ◆ Worksheet 11.2 Respiration equations Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 11: Teaching ideas

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Topic 2

Gas exchange in humans

Coursebook section 11.2 Teaching ideas ◆ ◆

Activity 11.5 Examining lungs, makes an attention-grabbing start to this topic.

Students may already know the names of most of the structures in Figure 11.2, so you could use a large, unlabelled diagram and ask the class to add labels to it. ◆ Explain how air moves down to the lungs by mass flow, but that individual molecules move across the wall of the alveoli into the blood by diffusion.

Common misunderstandings and misconceptions ◆

Students may confuse bronchi and bronchioles

Homework ideas ◆ ◆ ◆

Coursebook questions 11.7 to 11.10 End-of-chapter questions 2, 4 Workbook exercise 11.4 Gas exchange surfaces in rats

Topic 3

Breathing

Coursebook section 11.3 Teaching ideas ◆

Students often have trouble in understanding how movements of the ribs and diaphragm cause air to be drawn into and pushed out of the lungs. Activity 11.6 Modelling how the diaphragm helps with breathing, can help students to understand this topic. ◆ This is a suitable point at which comparisons of inspired and expired air can be made.

Activity 11.7 Gas exchange in small animals is always very memorable for students.

Activity 11.8 Comparing the carbon dioxide content of inspired air and expired air is worthwhile, and very easy to do. ◆ Investigating the effect of exercise on rate and depth of breathing, Activity 11.9, can also be dealt with now. Students will need to think back to what they have learnt about anaerobic respiration in human cells in order to explain oxygen debt.

Common misunderstandings and misconceptions ◆

Students frequently confuse cause and effect when attempting to explain how breathing movements are caused. ◆ They may think that muscles respire entirely anaerobically during exercise, rather than just ‘topping up’ the energy released by aerobic respiration with extra released by anaerobic respiration. ◆ They confuse heart rate with breathing rate.

Homework ideas ◆

End-of-chapter questions 3, 5, 6

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Chapter 11: Teaching ideas

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Teaching ideas Chapter 12

Excretion

Syllabus sections covered: 13

Teaching resources Syllabus section 13

13

40-minute periods

Resources in Coursebook

Excretory products

1

Questions 12.1 to 12.3

The human excretory system

2 to 4

Topic

Resources on this CD-ROM Worksheet 12.1 Excretion crossword

EOCQ 1 Activity 12.1 The structure of the kidney

Exercise 12.1 The human excretory system

Questions 12.4 to 12.11

Exercise 12.2 Dialysis

EOCQs 2, 3

Topic 1

Resources in Workbook

Worksheet 12.2 Excretory products and their removal

Excretory products

Coursebook sections 12.1, 12.2 Teaching ideas ◆

Students have already learnt about one excretory product – carbon dioxide produced in respiration – and this can be used to explain to them what excretion is, and how it differs from egestion. ◆ The production of nitrogenous waste involves an understanding of the structure of proteins (a string of amino acids) and the knowledge that amino acids contain the element nitrogen.

It is well worth recapping this information, perhaps quite extensively, before asking students to think about deamination. Figure 12.3 is very complex, so something similar could perhaps be built up step by step on the board or whiteboard, allowing students to think about each stage in the process in turn.

Common misunderstandings and misconceptions ◆ ◆ ◆

Excretion is frequently confused with egestion.

Students very often think that deamination happens in the kidneys.

They may think that sweating is done in order to excrete urea and salts; in fact, these substances are lost simply because the fluid secreted onto the skin to cool by evaporation happens to contain them.

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 12: Teaching ideas

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Homework ideas ◆ ◆ ◆

Coursebook questions 12.1 to 12.3 End-of-chapter question 1 Worksheet 12.1 Excretion crossword

Topic 2 The human excretory system Coursebook section 12.3 Teaching ideas ◆ ◆

Activity 12.1 The structure of the kidney, makes an attention-grabbing start to this topic.

Care must be taken not to go into too much detail about the structure and function of a nephron. Use the level of the detail in the Coursebook as guidance. ◆ Before dealing with dialysis, it may be worth recapping on students’ earlier work on diffusion and osmosis.

Common misunderstandings and misconceptions ◆ ◆

Students confuse urine and urea.

They often appear to think that there is a direct connection from the alimentary canal to the kidneys, along which waste liquids flow. ◆ They confuse ureters and urethra. ◆ As in osmosis, they may find it difficult to think of individual molecules and ions when considering dialysis.

Homework ideas ◆ ◆ ◆ ◆ ◆

Coursebook questions 12.4 to 12.11 End-of-chapter questions 2 and 3 Workbook exercise 12.1 The human excretory system Workbook exercise 12.2 Dialysis Worksheet 12.2 Excretory products and their removal

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Teaching ideas Chapter 13

Coordination and response

Syllabus sections covered: 14.1, 14.2, 14.3, 14.5

Teaching resources Syllabus section 14.1

Topic Coordination in animals; The human nervous system

40-minute periods

Resources in Coursebook

Resources in Workbook

Resources on this CD-ROM

2 to 4

Activity 13.1 Measuring reaction time using a ruler

Exercise 13.1 Caffeine and reaction time

Worksheet 13.1 The structure of a neurone

Activity 13.2 To measure mean reaction time

Worksheet 13.2 Reflex actions and voluntary actions

Questions 13.1 to 13.8 EOCQs 3, 4, 5 14.2

Receptors and sense organs; the eye

4 to 6

Activity 13.3 Can you always see the image?

Exercise 13.2 Accommodation in the eye

Worksheet 13.3 Structure and function in the eye Worksheet 13.4 Focusing

Activity 13.4 Looking at human eyes Activity 13.5 Dissecting a sheep’s eye Questions 13.9 to 13.18 EOCQs 1, 6 14.3

The endocrine system

1

Questions 13.19 to 13.22

14.5

Coordination and response in plants

4 to 6

Activity 13.6 To find out how shoots respond to light

Exercise 13.3 Auxin and tropism

Activity 13.7 To find out how roots respond to gravity Activity 13.8 To find out how auxin affects shoots Activity 13.9 To find out which part of a shoot is sensitive to light Questions 13.23 to 13.28 EOCQ 2

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 13: Teaching ideas

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Topic 1

Coordination in animals: The human nervous system

Coursebook sections 13.1, 13.2 Teaching ideas ◆

Once the students are settled, ask them all to stand up and then to sit down. Ask them how and why they did it. Use their answers to discuss the roles of receptors (in this case, their ears), coordination (the brain, where the response was decided on) and the effectors (in this case, the muscles they used in standing up). Explain that all animal coordination relies on receptors, coordination and effectors. ◆ If available, show students a model of the human nervous system. (Note that the names and functions of the different parts of the brain are not required.) ◆ Look at diagrams of neurones and discuss how they are similar to all animal cells, and how they are adapted to the functions of conducting nerve impulses. (Avoid saying they carry ‘messages’.) ◆ Activity 13.1 Measuring reaction time using a ruler uses very little apparatus and is a good starting point for planning exercises. You could also use one of the many sites on the Internet that measure reaction time. ◆ If you do Activity 13.2 To measure mean reaction time, you could ask one of the members of the ring to turn around with their back to the rest of the group. Show how the nerve impulse travels up their arm, into the spinal cord, up to their brain, back down to the spinal cord and then into the muscle in their other hand. You could perhaps place a large sheet of white paper against their back and draw the pathway on it. This can help students to understand what is being shown in stylised diagrams such as Figures 13.4 and 13.5.

Common misunderstandings and misconceptions ◆ ◆

Surprisingly, students sometimes believe that neurones travel around the body.

They may think that reflex actions ‘do not involve the brain’. This is not correct; many reflex arcs, including the iris reflex that they will learn about later, pass through the brain.

Homework ideas ◆ ◆ ◆ ◆ ◆

Coursebook questions 13.1 to 13.8 End-of-chapter questions 3, 4, and 5 Worksheet 13.1 The structure of a neurone Worksheet 13.2 Reflex actions and voluntary actions Workbook exercise 13.1 Caffeine and reaction time

Topic 2

Receptors and sense organs: the eye

Coursebook section 13.3 Teaching ideas ◆ ◆

Activity 13.4 Looking at human eyes, makes a good starting point for this lesson.

A model of an eye is very helpful, as it is a difficult structure to understand from a simple diagram of a section, such as is shown in Figure 13.10. ◆ Do Activity 13.5 Dissecting a sheep’s eye. Most students greatly enjoy dissecting an eye (despite many initial protests). Alternatively, you could do this as a demonstration. ◆ Activity 13.3 Can you always see the image? This can be used as a starting point to discuss the function of the retina.

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The way in which the ciliary muscle, suspensory ligaments and lens can change the focus of the eye is difficult to understand, but you can illustrate the effect of different sizes and shapes of lenses on parallel beams of light using apparatus borrowed from the physics department, who will probably give you advice on how to set it up and use it. Alternatively (or as well), a large, round-bottomed flask filled with fluorescin (a yellow–green fluorescent liquid) can be used to illustrate focusing. If you shine a narrow beam of light horizontally onto the flask, you will be able to see the path of the light rays through the liquid. Placing lenses of different types on the front surface of the rounded glass illustrates how the lens bends light rays. You can try using different combinations of lenses to bring parallel rays of light to a focus on the back surface of the flask. ◆ Step 4 in Activity 13.4 illustrates the pupil reflex, and this can be discussed at this point.

Common misunderstandings and misconceptions ◆

Students often forget that the light-receptive cells are in the retina, perhaps because this is at the back of the eye; they may think they are in the lens or elsewhere. ◆ They confuse the iris reflex and accommodation. ◆ They find it difficult to understand how contraction of the ciliary muscles can result in less tension on the lens.

Homework ideas ◆ ◆ ◆ ◆ ◆

Coursebook questions 13.9 to 13.18 End-of-chapter questions 1, and 6 Workbook exercise 13.2 Accommodation in the eye Worksheet 13.3 Structure and function in the eye Worksheet 13.4 Focusing

Topic 3 The endocrine system Coursebook section 13.4 Teaching ideas ◆

Use a big outline of the human body to show the positions of the endocrine glands illustrated in Figure 13.18. ◆ Ask students to tell you what happens in their body when they are very excited or frightened. Use this to explain the effects that adrenaline has, and how these help the body to prepare for action. ◆ Build up a comparison between nerves and hormones, using questioning, as a class exercise.

Common misunderstandings and misconceptions ◆

Students generally have no difficulty in understanding about hormones and the endocrine system.

Homework ideas ◆

Coursebook questions 13.19 to 13.22

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 13: Teaching ideas

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Topic 4

Coordination and response in plants

Coursebook section 13.5 Teaching ideas ◆

Show students a plant that has been left in a window and is growing towards the light. (They could possibly set this up in the previous lesson.) Alternatively, plants or young seedlings can be placed in a box with a slit in one side. Discuss why it is useful for the plant to respond to unidirectional light in this way. Introduce the term ‘tropism’ and its definition. ◆ Similarly, a plant could be left on its side, as in Figure 13.21 in the Coursebook, to illustrate the response of a shoot to gravity. ◆ Activity 13.6 To find out how shoots respond to light, needs to be left for a few days before results will be obtained. If you do not have a clinostat, the dish can simply be turned by hand several times a day, ensuring that approximately equal time is spent in each position. ◆ Students can use ideas from Activity 13.6 to plan their own experiment in Activity 13.7 To find out how roots respond to gravity. ◆ Activity 13.8 To find out how auxin affects shoots, and Activity 13.9 To find out which part of a shoot is sensitive to light, both require maize (or other cereal seeds) to be germinated before the lesson, so forward planning is required here. See the notes on these activities.

Common misunderstandings and misconceptions ◆

Students often find it difficult to imagine receptors and effectors in plants.

Homework ideas ◆ ◆ ◆

Coursebook questions 13.23 to 13.28 End-of-chapter question 2 Workbook exercise 13.3 Auxin and tropism

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Chapter 13: Teaching ideas

4

Teaching ideas Chapter 14

Homeostasis

Syllabus section covered: 14.4

Teaching resources Syllabus section 14.4

Topic Maintaining the internal environment; control of body temperature

40-minute periods

Resources in Coursebook

Resources in Workbook

Resources on this CD-ROM

3 to 4

Activity 14.1 Experiment to investigate the effect of size on rate of cooling

Exercise 14.1 Endotherms and ectotherms

Worksheet 14.1 Keeping warm

Activity 14.2 Investigating the effect of evaporation on the rate of cooling

Worksheet 14.2 Surviving hypothermia

Questions 14.1 to 14.6 EOCQ 3 14.4

Control of blood glucose concentration

2

EOCQs 1, 2, 4

Exercise 14.2 Diabetes

Topic 1

Maintaining the internal environment; control of body temperature

Coursebook sections 14.1, 14.2 Teaching ideas ◆

A quick quiz testing students’ understanding of the difference between heat and temperature could be helpful to you – it is worth checking what they have learnt about these concepts in physics lessons. ◆ Students may have used the term ‘cold-blooded’ to describe animals such as reptiles or fish. Ask them what this means, and guide the discussion towards the concepts of endotherms and ectotherms. (Note that the syllabus does not require them to know these terms, however.) ◆ Skin structure can be taught using a model, as well as projecting images of microscopic sections. ◆ Activity 14.1 Experiment to investigate the effect of size on rate of cooling, may have been done by students at an earlier stage, or in physics lessons. Activity 14.2 Investigating the effect of evaporation on the rate of cooling, asks students to build on this to plan their own experiment.

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Chapter 14: Teaching ideas

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Common misunderstandings and misconceptions ◆ ◆

Students often confuse heat with temperature.

They may not understand that when you ‘feel cold’, your internal body temperature is likely to be normal. ◆ Students do not always appreciate that it is the evaporation of water from sweat that has the cooling effect. Many think that sweat itself is cold, and therefore makes the skin feel cold. ◆ It is very common for students to think that blood vessels move up and down through the skin. ◆ They think that capillaries are able to change their diameter, rather than this happening as a result of the actions of muscles in the walls of arterioles.

Homework ideas ◆ ◆ ◆ ◆ ◆

Coursebook questions 14.1 to 14.6 End-of-chapter question 3 Worksheet 14.1 Keeping warm Worksheet 14.2 Surviving hypothermia Workbook exercise 14.1 Endotherms and ectotherms

Topic 2

Control of blood glucose concentration

Coursebook section 14.3 Teaching ideas ◆

If you know that a student has diabetes, talk to them in the days before this lesson to find out if they are happy for their condition to be discussed, or if they would prefer not to be brought into the limelight. If they agree, you could ask them to tell the class how they test their blood glucose levels, and why it is important that the blood glucose concentration is kept constant. However, be very careful not to put any pressure on a student to do this. ◆ A model of the body showing the position of the pancreas and liver can help students to visualise how these two organs act together in the control of blood glucose.

Common misunderstandings and misconceptions ◆

Glucagon and glycogen are often confused. It is essential that students learn to spell these words correctly. ◆ Students very frequently think that it is the hypothalamus that senses changes in blood glucose concentration, not the pancreas. ◆ They may think that insulin acts as an enzyme, breaking down glucose or changing it to glycogen. This is incorrect; insulin stimulates the liver to take action.

Homework ideas ◆ ◆

End-of-chapter questions 1, 2, and 4 Workbook exercise 14.2 Diabetes

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Chapter 14: Teaching ideas

2

Teaching ideas Chapter 15

Drugs

Syllabus sections covered: 15.1, 15.2, 15.3

Teaching resources Syllabus section

Topic

40-minute periods

15.1, 15.2

What is a drug?; Medicinal drugs

1

15.3

Misuse of drugs; Tobacco smoking

3

Resources in Coursebook

Resources in Workbook

Resources on this CD-ROM

EOCQs 1, 2, 3

Exercise 15.1 Alcohol and traffic accidents

Worksheet 15.1 Cigarette smoking

Exercise 15.2 Smoking and life expectancy

Worksheet 15.2 Cigarette smoking and lung cancer

Topic 1 What is a drug? Medicinal drugs Coursebook sections 15.1, 15.2 Teaching ideas ◆

Ask students if they have taken any drugs. Use their responses to list some examples of drugs that are used in medicine, drugs that are socially acceptable (for example, caffeine) and drugs that are abused. Discuss a definition of the term ‘drug’. ◆ Antibiotics can be discussed in relation to the work done on infectious disease in Chapter 10. It is recommended that the development of antibiotic resistance is dealt with when covering natural selection, in Chapter 19.

Common misunderstandings and misconceptions ◆

Students confuse antibiotics with antibodies.

Homework ideas ◆

Produce a poster explaining what a drug is.

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Chapter 15: Teaching ideas

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Topic 2

Misuse of drugs

Coursebook section 15.3 Teaching ideas ◆

Leaflets or other free material may be available to use in lessons about misuse of drugs, but you will need to check these carefully to ensure that they are suitable. ◆ Worksheet 15.2 Cigarette smoking and lung cancer, is a good data handling exercise and could be used in class. ◆ Workbook exercise 15.2 Smoking and life expectancy, is quite difficult and may be best done as a group or class exercise. ◆ Students may like to use the Internet to find examples of the misuse of anabolic steroids in sport.

Common misunderstandings and misconceptions ◆

Students may confuse reaction time and reaction speed, which can result in statements such as ‘drinking alcohol reduces your reaction time’.

Homework ideas ◆ ◆ ◆

End-of-chapter questions 1, 2, 3, and 4 Workbook exercise 15.1 Alcohol and traffic accidents Worksheet 15.1 Cigarette smoking

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Chapter 15: Teaching ideas

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Teaching ideas Chapter 16

Reproduction in plants

Syllabus sections covered: 16.1, 16.2, 16.3

Teaching resources Syllabus section 16.1, 16.2

16.3

40-minute periods

Resources in Coursebook

Asexual reproduction; sexual reproduction

1 to 2

Questions 16.1 to 16.12

Sexual reproduction in flowering plants: Pollination

2 to 4

Topic

Resources in Workbook

Resources on this CD-ROM

EOCQ 2

Activity 16.1 Investigating the structure of a flower Activity 16.2 Pollination Questions 16.13 to 16.17

Exercise 16.1 Grass pollen Exercise 16.2 Pollination in forests of different shapes and sizes

EOCQ 5 16.3

16.3

Sexual reproduction in flowering plants: Fertilisation and seed formation

1 to 3

Seed germination

1 to 3

Activity 16.3 Growing pollen tubes

Worksheet 16.1 Plant reproduction

Questions 16.18 to 16.20

Worksheet 16.2 Self- and cross-pollination

EOCQ 1 Activity 16.4 To find the conditions necessary for the germination of tomato seeds Activity 16.5 To find the effect of storage time on the germination rate of seeds Questions 16.21 to 16.25 EOCQ 3

16.3

Comparing asexual and sexual reproduction

1

Questions 16.26 to 16.27 EOCQ 4

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Chapter 16: Teaching ideas

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Topic 1 Asexual reproduction; sexual reproduction Coursebook sections 16.1, 16.2 Teaching ideas ◆

Show students at least one kind of plant reproducing asexually – whatever is available locally. You may be able to demonstrate several different methods of asexual reproduction taking place. Ask them what all of these methods of reproduction seem to have in common, looking for the idea that there is always only one parent. You could briefly introduce the idea of cell division by mitosis here, although a full treatment of this is best left until later, in Chapter 18. ◆ For comparison, now show a similar collection of plants with flowers and / or fruits.

Students may already know about flowers and pollen, so use questioning to find out what they already understand. Explain that sexual reproduction always involves gametes and fertilisation, and discuss in outline where the male and female gametes are in a flower, and how they get together. You can also briefly mention fertilisation in humans here, as well, in terms of the numbers of chromosomes in eggs and sperms, and how fertilisation restores the ‘correct’ numbers of chromosomes (Figure 16.3). ◆ A comparison of asexual and sexual reproduction is best left until later, once students have better knowledge of how these processes take place in flowering plants.

Common misunderstandings and misconceptions ◆

Students may think that sexual reproduction always involves two parents. This is not correct, as many flowers produce both male and female gametes and can fertilise themselves.

Homework ideas ◆ ◆

Coursebook questions 16.1 to 16.12 End-of-chapter question 2

Topic 2

Sexual reproduction in flowering plants: Pollination

Coursebook section 16.3 Teaching ideas ◆

Students will enjoy ‘dissecting’ a flower and sticking each of the parts into their notebooks.

Activity 16.1 Investigating the structure of a flower, describes how to do this. ◆ Activity 16.2 Pollination, is a planning exercise. Even if you do not wish to spend time on this activity, it is strongly recommended that you take students outside to observe insects and birds pollinating flowers. ◆ Anthers and pollen grains can be observed using a hand lens or a microscope, but take care with students who may be allergic to pollen. ◆ Students should see examples of wind-pollinated flowers, and compare these with insectpollinated or bird-pollinated flowers. ◆ Worksheet 16.2 Self- and cross-pollination, could be done now, but may be best left until after the next topic has been covered.

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 16: Teaching ideas

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Common misunderstandings and misconceptions ◆

Students may say that pollen grains are the male gametes, which is not correct. Pollen grains contain the male gametes. ◆ They may think that insects and birds deliberately carry pollen from one flower to another.

Homework ideas ◆ ◆ ◆ ◆

Coursebook questions 16.13 to 16.17 End-of-chapter question 5 Workbook exercise 16.1 Grass pollen Workbook exercise 16.2 Pollination in forests of different shapes and sizes

Topic 3 Sexual reproduction in flowering plants: Fertilisation and seed formation Coursebook section 16.3 Teaching ideas ◆

Activity 16.3 Growing pollen tubes, usually produces at least some successes, but some groups may not be able to see pollen tubes on their own slides and may need to look at those grown by other groups. ◆ Note that although students should learn how the male gamete reaches and fuses with the female gamete, and that the ovule becomes a seed, they do not need to know any more detail of seed formation.

Common misunderstandings and misconceptions ◆

It is very common for students to think that the entire pollen grain travels down through the style to the ovule.

Homework ideas ◆ ◆ ◆ ◆

Coursebook questions 16.18 to 16.20 End-of-chapter question 1 Worksheet 16.1 Plant reproduction Worksheet 16.2 Self- and cross-pollination

Topic 4

Seed germination

Coursebook section 16.3 Teaching ideas ◆

Students should have the opportunity to examine the structure of large seeds, such as beans, at first hand. This is easiest if the beans are soaked beforehand. ◆ Note that knowledge of the structure and dispersal of fruits is not required. ◆ Students should carry out an investigation into the conditions required for the germination of seeds, for example Activity 16.4. (Note that most seeds that we grow in gardens and as crops do not require light for germination, but many others do.) This can be used as a starting point for a planning exercise, such as Activity 16.5 To find the effect of storage time on the germination rate of seeds.

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 16: Teaching ideas

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Common misunderstandings and misconceptions ◆

There are no common problems with this topic.

Homework ideas ◆ ◆

Coursebook questions 16.21 to 16.25 End-of-chapter question 3

Topic 5

Comparing asexual and sexual reproduction

Coursebook section 16.4 Teaching ideas ◆

Now that students know how plants reproduce sexually, they can begin to think about why some plants do this, others reproduce asexually, and many use both methods. ◆ You could arrange a visit to a local nursery where large numbers of plants are produced by vegetative methods.

Common misunderstandings and misconceptions ◆

Students may suggest that either asexual or sexual reproduction is quicker than the other.

Neither is universally true.

Homework ideas ◆ ◆

Coursebook questions 16.26 to 16.27 End-of-chapter question 4

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Chapter 16: Teaching ideas

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Teaching ideas Chapter 17

Reproduction in humans

Syllabus sections covered: 16.4, 16.5, 16.6, 16.7

Teaching resources Syllabus section 16.4

16.4

40-minute periods

Resources in Coursebook

Resources in Workbook

Human reproductive organs

2 to 3

Questions 17.1 to 17.2

Exercise 17.1 Gametes

Fertilisation and development

3 to 4

Topic

EOCQs 2, 5 Questions 17.3 to 17.13 EOCQs 3, 4

Resources on this CD-ROM

Exercise 17.2 Gas exchange in the placenta and lungs Exercise 17.3 Breast-feeding statistics

16.5

The menstrual cycle

2

Questions 17.14 to 17.18

16.6

Birth control

2

16.7

Sexually transmitted infections

2 to 3

Topic 1

Human reproductive organs

Worksheet 17.1 The menstrual cycle

EOCQ 1 Exercise 17.4 Birth control data EOCQ 6

Worksheet 17.2 AIDS in the Caribbean

Coursebook sections 17.1 Teaching ideas ◆

If available, three-dimensional models are very helpful in understanding the relative positions and sizes of the reproductive organs. ◆ Workbook exercise 17.1 Gametes, gives practice in thinking about how particular cells are adapted for their functions.

Common misunderstandings and misconceptions ◆

Students may already have some knowledge of this topic before the lessons, but this is often muddled and incorrect. ◆ They may have a tendency to use everyday language, rather than scientific language.

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 17: Teaching ideas

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Homework ideas ◆ ◆

End-of-chapter questions 2, 5 Workbook exercise 17.1 Gametes

Topic 2

Fertilisation and development

Coursebook section 17.2 Teaching ideas ◆

You may be able to show students video clips of sea urchin sperm fertilising eggs. Search on the internet for ‘sea urchin fertilisation’ videos. ◆ Ensure that students understand that fertilisation actually happens when the nuclei of the male and female gametes fuse. ◆ There are many new terms to learn in this topic, and these can cause confusion. Use Figure 17.12 as an overall summary of the sequence, and to make sure students know where each of the processes takes place. ◆ Note that no detail of the structure of the placenta is required, but students will need some kind of image to help them to understand how it functions.

Common misunderstandings and misconceptions ◆ ◆

Students may think that only the chromosomes of the sperm enter the egg.

There is often confusion about the term ‘zygote’. This is the cell that is produced immediately as the result of the fusion of the sperm and egg. ◆ Students may think that fertilisation happens in the vagina, cervix or uterus, or even in the ovary. ◆ It is common for them to believe that the mother’s blood mixes with the fetus’s blood in the placenta.

Homework ideas ◆

Coursebook questions 17.3 to 17.13 ◆ End-of-chapter questions 3, and 4 ◆ Workbook exercise 17.2 Gas exchange in the placenta and lungs ◆ Workbook exercise 17.3 Breast-feeding statistics

Topic 3 The menstrual cycle Coursebook section 17.3 Teaching ideas ◆

It is probably best to deal first with the changes in the lining of the uterus, and then with the hormonal changes that bring this about. The various diagrams in Figure 17.20 need to be dealt with step by step, rather than trying to understand all of them at once.

Common misunderstandings and misconceptions ◆ ◆

Students often use the term ‘uterus wall’ when they mean ‘uterus lining’.

They may think that the pituitary gland secretes oestrogen or progesterone.

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Chapter 17: Teaching ideas

2

Homework ideas ◆ ◆

Coursebook questions 17.14 to 17.18 Worksheet 17.1 The menstrual cycle

Topic 4

Birth control

Coursebook section 17.4 Teaching ideas ◆

You may be able to arrange a visit by someone from the local health centre who can demonstrate methods of birth control.

Common misunderstandings and misconceptions ◆

There are no common problems with this topic.

Homework ideas ◆

Workbook exercise 17.4 Birth control data

Topic 5

Sexually transmitted infections

Coursebook section 17.5 Teaching ideas ◆ ◆

Local health centres may have posters or leaflets that you can use for this topic.

It is a good idea to find out what students think they already know about HIV/AIDS, as there are many entrenched misconceptions in some countries. It may be difficult for them to leave these behind them as they learn to think about the topic scientifically.

Common misunderstandings and misconceptions ◆

Students may think that AIDS is caused by genes, because they know it can be transmitted from mother to child.

Homework ideas ◆ ◆

End-of-chapter question 6 Worksheet 17.2 AIDS in the Caribbean

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Chapter 17: Teaching ideas

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Teaching ideas Chapter 18

Inheritance

Syllabus sections covered: 17.1, 17.2, 17.3, 17.4, 17.5

Teaching resources Syllabus section

Topic

40-minute periods

Resources in Coursebook

17.1, 17.3, 17.4 17.2

Resources in Workbook

Resources on this CD-ROM

Chromosomes; cell division

3 to 4

Questions 18.1 and 18.2

Worksheet 18.1 Mitosis and meiosis

Genes and alleles

2

Questions 18.3 to 18.7

Worksheet 18.2 Genotypes and phenotypes

EOCQs 1, 2 17.5

Inheriting genes

3 to 5

Activity 18.1 ‘Breeding’ beads Questions 18.8 to 18.14 EOCQs 4, 5, 6, 8

Exercise 18.1 Fruit fly inheritance Exercise 18.2 Black and chestnut horses Exercise 18.3 Pedigree

17.5

Sex inheritance; sex linkage

2 to 3

Question 18.15

17.2

DNA and protein synthesis

1 to 2

Topic 1

Chromosomes; cell division

EOCQ 7

Exercise 18.4 Sex linkage in fruit flies

EOCQ 3

Coursebook sections 18.1 Teaching ideas ◆

Show students scanning electronmicrographs of chromosomes (there are plenty on the Internet). Explain that each one is a long molecule of DNA, various sections of which are genes coding for the production of proteins. Discussion of karyotypes, such as those in Figures 18.3 and 18.4 in the Coursebook, will also help students to understand what chromosomes are. It is worth emphasising that the chromosomes don’t really line up like this, but that these images have been produced by ‘cutting out’ images of each chromosome and rearranging them. ◆ Mitosis can be modelled using long pieces of coloured string, wire or other material to represent chromosomes. Use a small number – say six pieces, making up three pairs. Place them on the bench top, or perhaps on an overhead projector, and surround them by two Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 18: Teaching ideas

1

concentric circles of string to represent the nuclear envelope and cell membrane. Produce an identical partner for each ‘chromosome’, and wrap them round each other once to form a ‘centromere’ linking the two ‘chromatids’. Remove the nuclear envelope. Move the chromosomes so they line up at the centre of the cell, then pull the chromatids apart and take them to each end of the cell. Place string around each one to represent a new nuclear envelope. Students do not need to know any details of the stages of this process, so keep this very simple, concentrating on the production of two new daughter cells with exactly the same number and type of chromosomes as the original cell. ◆ Meiosis can be modelled in a similar way. Once again, do not go into too much detail.

Concentrate on the production of haploid cells from diploid. You could perhaps show different alleles of the same genes on some of the homologous pairs by tying little pieces of different coloured cotton to the chromosomes and showing how these can end up in different combinations in the daughter cells. However, the concept of independent assortment is a difficult one, and is not required by the syllabus, so do not go too far with this model. ◆ There are many definitions associated with this topic. Groups could race to match cards on which a definition has been written with other cards on which a term has been written.

Common misunderstandings and misconceptions ◆ ◆

Students can become confused about chromosomes, genes and alleles.

They may also confuse the terms ‘chromosome’, ‘chromatid’ and ‘centromere’.

Homework ideas ◆ ◆ ◆

Use the internet to find the chromosome numbers of 10 species of organism.

Coursebook questions 18.1 to 18.2 Worksheet 18.1 Mitosis and meiosis

Topic 2

Genes and alleles

Coursebook section 18.2 Teaching ideas ◆

Through discussion, bring out the idea that a diploid cell has two copies of each gene.

Introduce the term ‘allele’ and then consider the different combinations of alleles there can be in cells, if there are two alleles of a gene. ◆ Give students plenty of practice in using the terms ‘gene’, ‘allele’, ‘dominant’, ‘recessive’, ‘homozygous’, ‘heterozygous’, ‘genotype’ and ‘phenotype’ by posing questions along the lines of Question 18.4 in the Coursebook. It is essential that students have a sound grasp of these concepts before starting to think about how genes are passed on to the next generation. It is suggested that you do not consider genes in gametes, or genetic crosses, until you move on to the next topic.

Common misunderstandings and misconceptions ◆

The large number of new terms can cause confusion.

Homework ideas ◆ ◆ ◆

Coursebook questions 18.3 to 18.7 End-of-chapter questions 1, and 2 Worksheet 18.2 Genotypes and phenotypes Original material © Cambridge University Press 2014

© Cambridge University Press 2014 IGCSE Biology

Chapter 18: Teaching ideas

2

Topic 3

Inheriting genes

Coursebook section 18.3 Teaching ideas ◆

Begin by discussing the fact that gametes have only one copy of each gene. Consider the different genotypes of gametes that can be produced by homozygous and heterozygous organisms. Give students practice in this before moving to the next step. ◆ Now consider how the fusion of gametes with different genotypes can produce zygotes with different genotypes. Introduce the format of genetic diagrams, following the style shown on page 238 in the coursebook. Ensure that students understand what these diagrams are showing. Note that the ‘gametes’ line should show the different gametes that are produced.

For a homozygote, only one type is produced and so only one should be shown, as on page 238. ◆ It is suggested that Punnett squares are a better way of showing what happens when different combinations of gametes fuse than joining them with lines. It is much less easy to make an error. If the squares are made large enough, students can write the phenotype of each resulting genotype inside them. ◆ If students have access to the Internet, there are various simulations that they could use to carry out virtual genetic crosses. ◆ Students will benefit from plenty of repetitive practice with genetic crosses. Ensure that they do not take shortcuts, but always write the cross out fully. ◆ Activity 18.1 ‘Breeding’ beads, can help students to understand that genetics is all about probabilities.

Common misunderstandings and misconceptions ◆

Many students always write down two gametes from each parent, even if only one type is produced. This makes extra work when working out the possible offspring genotypes, and also indicates that they do not understand what they are doing and why. ◆ They may think that each cross produces four offspring. ◆ Students often take shortcuts, missing out stages in the genetic diagram, which may prevent them achieving full marks in an examination question. ◆ They may draw only a Punnett square, rather than a complete genetic diagram.

Homework ideas ◆ ◆ ◆ ◆ ◆

Coursebook questions 18.8 to 18.14 End-of-chapter questions 4, 5, 6 and 8 Workbook exercise 18.1 Fruit fly inheritance Workbook exercise 18.2 Black and chestnut horses Workbook exercise 18.3 Pedigree

Topic 4

Sex inheritance; sex linkage

Coursebook section 18.3 Teaching ideas ◆

Once again, it is important to establish an understanding of the genotypes and phenotypes associated with sex-linked characteristics, before trying to look at how these are inherited.

Original material © Cambridge University Press 2014

© Cambridge University Press 2014 IGCSE Biology

Chapter 18: Teaching ideas

3

Common misunderstandings and misconceptions ◆

Sex linkage is a difficult topic, and students may manage to answer questions without a deep understanding of what they are doing. ◆ Students often forget to write the symbol for the X chromosome as well as that of the allele it carries.

Homework ideas ◆ ◆ ◆

Coursebook question 18.15 End-of-chapter question 7 Workbook exercise 18.4 Sex linkage in fruit flies

Topic 5

DNA and protein synthesis

Coursebook section 18.4 Teaching ideas ◆

It is very important to keep this topic sufficiently simple for IGCSE students to understand.

They will deal with it in more detail if they continue to AS level. ◆ Look on the Internet for suitable animations showing how mRNA is made from DNA and how proteins are assembled on ribosomes. Choose carefully and do not allow students to become confused by too much information.

Common misunderstandings and misconceptions ◆

Students often confuse bases with amino acids.

Homework ideas ◆

End-of-chapter question 3

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 18: Teaching ideas

4

Teaching ideas Chapter 19 Variation and natural selection Syllabus sections covered: 18.1, 18.2, 18.3

Teaching resources Syllabus section

Topic

40-minute periods

Resources in Coursebook

18.1

Variation

2 to 4

Activity 19.1 Measuring variation

Resources in Workbook

Resources on this CD-ROM Worksheet 19.1 How different are you?

Questions 19.1 to 19.2

Worksheet 19.2 Genes for obesity

EOCQs 1, 4 18.2

Adaptive features

2 to 3

Question 19.3

Exercise 19.1 Water hyacinth experiment

18.1, 18.3

Selection

2 to 5

Questions 19.4 to 19.7

Exercise 19.2 Big-horn sheep

EOCQs 3, 5 18.3

Selective breeding

2 to 3

Questions 19.8 to 19.9 EOCQ 2

Exercise 19.3 Selective breeding for high milk yield

Topic 1 Variation Coursebook section 19.1 Teaching ideas ◆

You could begin this topic with Worksheet 19.1 How different are you? Students can then use their findings to think about discontinuous and continuous variation and about its causes. ◆ Activity 19.1 Measuring variation, could be done as described, or you could use seeds, leaves or any other biological samples that are available in large numbers and have measurable variation. ◆ You may be able to find images on the Internet of organisms showing characteristics caused by mutations (but take care not to use unsuitable images). Ensure that students appreciate that mutations can occur spontaneously, but that the chance of this happening is increased by various environmental factors. ◆ Worksheet 19.2 Genes for obesity, could form the basis of a class discussion about the difficulty of finding out which of our characteristics are affected by genes. ◆ It is suggested that you leave sickle-cell anaemia until a little later, when you are dealing with selection.

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 19: Teaching ideas

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Common misunderstandings and misconceptions ◆

Students very commonly have difficulties with the terms ‘continuous variation’ and ‘discontinuous variation’. They may think that continuous variation is something that changes with time. ◆ Some students may not appreciate that changes to characteristics caused by the environment do not affect genes and therefore cannot be inherited.

Homework ideas ◆ ◆

Coursebook questions 19.1 to 19.2 End-of-chapter questions 1, 4

Topic 2 Adaptive features Coursebook section 19.2 Teaching ideas ◆

This topic is best taught by showing students plants and animals that have very clear adaptations for a particular environment. They can practice their observation and recording skills by making labelled diagrams.

Common misunderstandings and misconceptions ◆

There are no common problems with this topic.

Homework ideas ◆ ◆

Coursebook question 19.3 Workbook exercise 19.1 Water hyacinth experiment

Topic 3

Selection

Coursebook section 19.3 Teaching ideas ◆

Use a particular example — for example, the cacti in Figure 19.12, or the peppered moths described on pages 255–257, or a locally familiar example – to help students to appreciate how individuals with a particular characteristic have a better chance of survival than others. Make sure they are secure with this concept before thinking about the next generation. ◆ Now discuss the idea that it is the organisms with this advantageous variation that will be most likely to live long enough to reproduce. If the variation was caused by genes, then the advantageous alleles they possess are more likely to be passed on to the next generation than the other alleles possessed by other individuals. ◆ The evolution of antibiotic resistance in bacteria can be linked back to work on pathogens done earlier. ◆ There are various interactive games simulating natural selection, available on the Internet.

Check them out carefully, however, before deciding to use them. A good one involving peppered moths can be found at http://www.biologycorner.com/lesson-plans/evolutiontaxonomy/.

Original material © Cambridge University Press 2014 © Cambridge University Press 2014 IGCSE Biology

Chapter 19: Teaching ideas

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◆

Sickle cell anaemia provides a complete story beginning with mutation and how this causes variation, then looking at differential selection pressures on individuals with different genotypes, and finally relating this to current distributions of the mutant allele. This is a very good example, but linking together so many ideas can be difficult for all but the most able students.

Common misunderstandings and misconceptions ◆

It is common for students to think that organisms purposefully change their characteristics to become better adapted for their environment. ◆ They may try to explain selection in terms of the whole current population changing characteristics, rather than considering the individuals within the population.

Homework ideas ◆ ◆ ◆

Coursebook questions 19.4 to 19.7 End-of-chapter questions 3, and 5 Workbook exercise 19.2 Big-horn sheep

Topic 4

Selective breeding

Coursebook section 19.3 Teaching ideas ◆

Artificial selection could be discussed with reference to a crop or animal that is familiar to students. ◆ Provide students with a set of images of different breeds of an animal — say dogs, horses or goats. Ask them to describe how they would use individuals of these breeds to produce a different breed with a particular set of characteristics (for example, long ears and a short tail). Ensure that they appreciate that the selection process has to go on for many generations and will not be achieved in one go.

Common misunderstandings and misconceptions ◆

Students frequently fail to appreciate that selection has to take place over many generations in order to achieve a population with the desired characteristics. ◆ If they are discussing breeding cattle for high milk yield, they may not realise that bulls do not produce milk. ◆ Students often confuse artificial selection with genetic engineering. They should appreciate that genetic engineering is done only rarely, because it is very expensive, and requires highly trained people and good laboratory facilities. Artificial selection, on the other hand, has been done for centuries and is still by the far most widely used method of breeding new varieties of crops or animals.

Homework ideas ◆ ◆ ◆

Coursebook question 19.8 to 19.9 End-of-chapter question 2 Workbook exercise 19.3 Selective breeding for high milk yield

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Teaching ideas Chapter 20 Organisms and their environment Syllabus sections covered: 19.1, 19.2, 19.3, 19.4

Teaching resources Syllabus section 19.1, 19.2

Topic Ecology, Energy flow

40-minute periods

Resources in Coursebook

Resources in Workbook

Resources on this CD-ROM

2 to 6

Activity 20.1 Studying an ecosystem

Exercise 20.1 Energy transfer in a food chain

Worksheet 20.1 A boreal forest food web

Activity 20.2 Investigating the food preferences of slugs Questions 20.1 to 20.7 EOCQs 2, 6 19.3

Nutrient cycles

3 to 5

EOCQs 1, 3, 4

Exercise 20.2 Fish tank

19.4

Population size

3 to 4

EOCQs 5, 7

Exercise 20.3 Goats on an island

Topic 1

Ecology; Energy flow

Worksheet 20.2 Population growth

Coursebook sections 20.1, 20.2 Teaching ideas ◆

If at all possible, take students outside to study a local ecosystem. Even the smallest area of grass or woodland close to the school will provide enough organisms for them to be able to suggest food chains and webs. Activity 20.1 Studying an ecosystem, provides suggestions about how students could collect and interpret information. ◆ Activity 20.2 Investigating the food preferences of slugs, can provide an alternative way of investigating live organisms, if you are not able to take students outside. However, it is also valuable in its own right and could be done as well as Activity 20.1. It provides good practice in interpreting results and evaluating their reliability. You could try this with whichever animals are easily available locally (e.g. snails, locusts or other insects).

Take care that they are not stressed, and return them to their natural habitat once the experiment is complete.

Common misunderstandings and misconceptions ◆

At this level, students should be expected to state that the arrows in a food chain represent transfer of energy, not just ‘is eaten by’.

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Chapter 20: Teaching ideas

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Students very frequently fail to realise that the boxes in a pyramid are a quantitative representation of the numbers or biomass of organisms, where the area of the box represents a particular number or mass. A ‘triangle’ is not a suitable way of showing such a pyramid. ◆ They may think that a smaller box means that an organism at that trophic level has a smaller energy content than one at a lower trophic level. They fail to understand that the boxes represent the total numbers or biomass of all the organisms at that trophic level.

Homework ideas ◆ ◆ ◆ ◆

Coursebook questions 20.1 to 20.7 End-of-chapter questions 2, 6 Workbook exercise 20.1, Energy transfer in a food chain Worksheet 20.1 A boreal forest food web

Topic 2

Nutrient cycles

Coursebook section 20.3 Teaching ideas ◆

It is likely that students will already have met the carbon and water cycles, so you may be able to build each of these up (on the board, for example) using suggestions and contributions from the class. This is much more effective than simply presenting them with ready-made flow diagrams. ◆ Different students could be placed in the room to represent different parts of the carbon cycle. For example, a small circle of students could represent the air; another group could represent the leaves, stem and roots of a plant; another could represent decomposers in the soil, another a grazing animal and so on. Ask one person to be, for example, a carbon atom in a carbon dioxide molecule in the air, and to move between the different groups until the atom is part of a cell in the ‘animal’. Referees can be appointed to make sure that the chosen routes are valid, or to ask the ‘carbon atom’ what it thinks it is doing or what is happening to it. ◆ The nitrogen cycle is much more difficult for students to understand than the carbon cycle.

The fundamental difficulty lies in the widespread use of the term ‘nitrogen’ to mean any form of nitrogen, including nitrogen compounds. It will become easier if you use the term ‘nitrogen’ to mean only a nitrogen atom or nitrogen gas, and always refer to compounds of nitrogen by their names – for example, nitrates, proteins, urea. ◆ As for the carbon and water cycles, students will find it easier to understand the nitrogen cycle if it is built up gradually through discussion, preferably using contributions from the class.

Common misunderstandings and misconceptions ◆

Students often do not appreciate that gaseous water is invisible and that it is only when it condenses to form tiny water droplets that clouds are formed. ◆ They may think that solutes, such as salt, evaporate from the sea along with the water. ◆ They may use the term ‘fossilisation’ to describe the formation of fossil fuels, which is not correct. Fossilisation means the formation of fossils, which are the remains of living organisms that have turned to rock. Most fossil fuels are not fossils (e.g. natural gas, oil).

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Students who have a poor understanding of elements, compounds, ions and molecules may struggle to understand the nitrogen cycle. ◆ They may say that nitrogen gas cannot be ‘absorbed’ by living organisms. This is incorrect – nitrogen gas is easily absorbed across gas exchange surfaces. However, it cannot be used by most organisms, because it is too unreactive.

Homework ideas ◆ ◆

End-of-chapter questions 1, 3, 4 Workbook exercise 20.2 Fish tank

Topic 3

Population size

Coursebook section 20.4 Teaching ideas ◆

The ‘yeast in a flask’ scenario (Figure 20.12) is a good way of introducing students to the concepts involved in population growth, as they generally find it easy to visualise and can understand why the population cannot grow for ever. Alternatively, you could discuss what might happen if a few rabbits or other animals were introduced to an island. ◆ Age pyramids (Figure 20.14) could be introduced by looking at a current one for the country in which your school or college is situated – there are numerous sites on the Internet where this information can be found. Then choose another country with a contrasting shape of age pyramid and, through discussion, help students to appreciate what different shapes of pyramid convey about how the population is changing in size and composition.

Common misunderstandings and misconceptions ◆

Students may say that the population of yeast cells in a flask, or a population of rabbits on an island, stops growing because they ‘run out of space’. Space in itself is rarely likely to be a significant problem for any population – it is far more likely that a factor such as food supply or suitable breeding sites is limiting.

Homework ideas ◆ ◆ ◆

End-of-chapter questions 5, 7 Workbook exercise 20.3 Goats on an island Worksheet 20.2 Population growth

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