It is possible to learn about the function of lungs from the diagrams and pictures supplied in the workbook. However, dissecting the real organ is hugely beneficial to the learners and will help them to understand the structure of the lungs and how this relates to their function. If however, you are not able to do the dissection, you can watch some of the videos supplied.

This will depend on how many lungs you are able to obtain and how many learners are willing to do the dissecting. A suggestion is to break learners up into groups, or else do the dissection as a demonstration in front of the class, especially if you have a big class or many Gr. 8 classes. The following materials are required for each dissection, whether in a group or to be done as a demonstration.

Sometimes the main sections of lung tissue are cut into at the abattoir (as part of the inspection process). You can approach the butcher well in advance and discuss what you need so that they can limit damage to the material and provide lungs as whole as possible. Butchers often refer to it as 'pluck' which contains the lungs and part of the heart.

Ethical issues

Before starting this lesson, find out if any learners are sensitive to the use of animal products in this way, or even to the fact that animals are farmed for human consumption. Some learners may also have religious or cultural objections to the dissection and handling of animal parts, especially cows and pigs. You need to be aware of these issues and be sensitive to them.

These hard rings are are made of cartilage and keep the trachea open so air can move freely. Encourage learners to make notes of their observations throughout the dissection.

The following diagram gives an example of something the learners might produce. You can also draw this up on the board when describing oxygen and carbon dioxide diffusion.

Possible headings that learners might write are:

• Gaseous exchange within the lungs
• Diffusion of carbon dioxide and oxygen within the lungs
• Diffusion of CO₂ and O₂ between the alveolus and capillary
• etc

Learners will look at the heart in much more detail in Gr. 10 Life Sciences where the detailed structure of the heart will be studied, including the the valves. This activity is meant as an introduction to the structure of the heart and for learners to experience a dissection. We suggest doing this as a demonstration as learners will do this practical in Gr. 10 Life Sciences again.

It is important to be tolerant of learners religious, cultural or personal beliefs which may prevent them from participating in this dissection, particularly if pig is used. A suggestion is to break learners up into groups, or else do the dissection as a demonstration in front of the class. The following materials are required for each dissection, whether in a group or when done as a demonstration. The number of groups will depend on how many hearts you are able to obtain and how many learners are willing to do the dissecting. For learners who are unwilling to handle the hearts, but still want to be involved, they could take photographs of the heart at different stages of the dissection using a digital camera or their mobile phone cameras.

Sometimes butchers will cut the blood vessels off the top of the heart, and may also remove the atria and cut into the ventricles at the abattoir. Discuss your needs with the butcher beforehand so that they can preserve the heart as much as possible. You can sometimes even obtain the heart and lungs together (usually referred to as a 'pluck'), which is useful to see how the blood vessels connect the organs. If you obtain hearts with long blood vessels, attached, cut off some of these sections to keep for studies of veins and arteries. As with the lung dissection, be sensitive to ethical issues and learners' concerns around the use of animal products in this way.

Learners should be able to feel the valves at the base of the aorta. These will become visible later when viewing the internal structure of the heart.

The heart muscle also needs a supply of blood and oxygen in order to function. This is supplied by the coronary arteries. Learners should be encouraged to take notes in their workbooks or a separate notebook throughout the dissection.

To locate which side is which in the heart, learners must hold the heart so that the coronary artery runs diagonally across the heart - this will be the the front. Then the left / right ventricles are on either side of the coronary arteries.

The aortic valve prevents the backflow of blood into the heart once it has been pumped out and into the aorta to travel to the rest of the body.

At this stage, you can also point out some of the other valves to the learners. This detail is not necessary to know, but it is very interesting when thinking about how the heart functions as a very efficient pump. Look at the areas where the atria and ventricles join to locate the bicuspid valve between the left atrium and ventricle, and the tricuspid valve between the right atrium and ventricle. They should be visible as thin flaps of tissue with tough "threads" or cords attached to the base of the flaps. The tricuspid valve on the right should have 3 flaps and the bicuspid valve on the left should have 2.

Later in this chapter learners are going do an investigation into their heart rate at rest and after exercise and they will then need to be quite skilled in taking their pulse and determining their heart rate. This activity is therefore included in preparation for this. You can get learners to all find their pulse in the way they find easiest. Once they have done this, get them to count their heart rate while you time for 30 seconds, indicating "Stop" and "Start". To obtain their heart rate at beats per minute, learners then multiply by 2.

Other units of measurement which indicate a rate are for example: km/h (kilometers per hour), m/s (meters per second), flow rate of a river in l/s (litres per second), etc.

Where possible teachers should set up the following activity in advance of the class arriving. It is aimed specifically at 'kinetic' learners to make them 'walk the circulatory system' in order to remember how it works.

Materials needed:

• 3 hula hoops, or something similar
• white A4 sheets
• coloured paper
• red and blue string
• prestik

Preparation for the lesson:

1. Cut up coloured paper into blocks - you will need two different colours
2. there should be enough blocks for each learner in the class to have at least one of each colour.
3. one colour will represent oxygen and the other colour will represent carbon dioxide.

1. Make the following signs on the back of recycled A4 pages - write in a clear, neat font so everyone can see it.
2. Left side of heart
3. Right side of heart
4. Lungs
5. Arms and hands
6. Legs and feet
7. Brain
8. Stomach
9. Kidneys
10. Face

[There are many other body parts that could be included and teachers are welcome to add to this list. For the purposes of this activity though time constraints were considered and it was decided to add only those listed here.]

1. Obtain the use of a large, open space, either in your classroom, a hall, or outside on the grass. Imagine a huge person is lying out on the space.
2. Lay out 2 hula hoops to represent the left and right side of the heart.
3. Place one more hula hoop above this to represent the lungs.
4. Lay out the signs on the A4 pages to illustrate where each of the body parts will be in relation to the heart and lungs.
5. Stick red wool (for oxygen carrying vessels) and blue wool (for carbon dioxide carrying vessels) with prestik or sellotape to the A4 posters (and between them) forming a large circulatory system as in the diagram in the activity.
6. Leave a pile of red and blue blocks of paper at each body part - it works well if you put these in ice-cream or yoghurt tubs
7. Learners start off in the lungs and will walk along the red lines to their different body parts as if they are traveling in the blood vessel to deliver oxygen. When they have delivered their oxygen (by dropping off the red blocks and picking up blue blocks) they will then travel along the blue lines to deliver carbon dioxide to the lungs and to get more oxygen.
8. As one learner leaves the lungs, send another one off so that you have several learners walking through the system at any one point.
9. If you have a large class, let a couple of learners walk through at a time. If you make the layout really big, then the whole class can form a long line of individual blood cells and move through in a line.

Make sure learners are able to visualise that they are forming a complete cycle or system which repeats. If they are battling, you can walk through it with them first to explain. The first time you could even demonstrate the activity by starting in the lungs and getting learners to instruct you on where to walk to next.

Get learners to do this activity in the 3 days leading up to the lesson where you will investigate the effect of exercise on heart rate.

For this investigation, the basic instructions are given below, and then learners will have to design the investigation themselves. A suggestion is to break your class up into big groups of at least 10 learners. They can then discuss how they are going to do the investigation. Each learner must write down their own method and design after they have discussed how they are going to do the recordings within their group. The only materials that learners will need are timing devices - you can either provide some stopwatches, or learners can use the stopwatch on their mobile phones. If learners opt to run for example, suggest running on the spot, as it will be difficult otherwise to control how far or fast individual learners will run in 2 minutes. In general, fitter people have a slower resting heart rate and return to their resting heart rate faster than unfit people after a bout of exercise, but the focus for this activity should be that learners take objective measurements and analyse the data that they collect appropriately. Therefore if the findings of the investigation do not agree with the expected results, full credit should still be given for an accurate interpretation.

This is the first investigation that learners will be conducting in Gr. 9. An interesting video to watch beforehand about the scientific method is given in the visit box and titled "The times and troubles of the Scientific Method". It could be an interesting class exercise to watch this video first and then have a class discussion about learners' understanding of the scientific method. At school level, the scientific method is taught in specific steps, but it is very important for learners to also understand how science discoveries often take place at university level and that they often happen by chance or as a side result of another experiment.

The aim could vary slightly from one group to the next, but in general the aim is to see what the effect is of exercise on heart rate and to make deductions about class fitness.

A possible extension:

Investigate how quickly a learner's heart rate returns to resting heart rate after physical activity. This will indicate how much their heart rate increased during the exercise as you will measure before and after activity. But then you can also measure the heart rate at 1 minute intervals after the exercise to see how quickly the heart rate decreases to resting rate again. This gives a more rounded measure of fitness level as the faster a person is able to recover, the more fit they are. This should only be done as an extension if you feel your learners are capable and have time to do it within the lesson. This graph would be a line graph.

A possible hypothesis which learners might propose is: "Heart rate increases after exercise."

Make sure learners discuss all aspects of the investigation. You can help learners with this part of their discussion in their groups by pointing out questions that they should answer when writing their method. For example, how will we do the recording? This will depend on how many skipping ropes are available if they are to be used. Will one learner skip at a time while the others watch and record the time? Or if the learners are to jog on the spot for 2 minutes, then perhaps 5 learners can jog at once while the other 5 do the recordings. Learners must specify how they will record heart rate and where. Will it be on the wrist or the neck? Is it best to record heart rate for 10 (or 15) seconds and multiply 6 (or 4) to get the beats per minute? This is because if they record the heart rate for a whole minute after exercise, the rate might have started to slow down already by the end of the minute and therefore not be an accurate reflection of the heart rate immediately after exercise.

A possible table that learners might produce could look as follows:

Table showing the heart rate of 10 learners before and after 2 minutes of skipping

Learners may also come up with additional columns, for example they may add a column to calculate the change in heart rate from before exercise to immediately after exercise.

Learners may not understand how a double bar graph is different from a bar graph, and may not understand what is meant by two sets of data. An example of a double bar graph would be the minimum and maximum temperatures on different days of the week. In this example, the day of the week is the independent variable, and we are looking at two dependent variables (two sets of data) - namely the maximum and minimum temperatures. For a graph like this, one would indicate "days of the week" on the x-axis, and you would have two bars next to each other for each day. One would show the minimum temperature and one would show the maximum temperature. The bars showing the two temperatures would touch, and the days of the week would be separated by a space.

Learners might find this difficult to answer, but it is crucial that they understand the types of graphs and when each one should be used. In this investigation, we want to show the data for each learner along the independent axis (x-axis). The learners are not related in any way, nor are they numerical values - they are discrete categories described by words (ie. the name of the learner). We will therefore use a bar graph. In this investigation we will actually be using a double bar graph. There will be two bars for each learner - the first bar being the heart rate before exercise and the second bar being the heart rate after exercise.

Learners can distinguish between the before and after readings by creating a key where the one set of data is in one colour or pattern and the other set is in another colour or pattern.

When looking at learners' graphs or helping them to draw them, make sure they have the heart rate in beats/min on the dependent y-axis and the learners names on the independent x-axis. Each learner will have two bars, one for heart rate before exercise and one for heart rate after exercise. For each learner, these two bars should be touching, but there should be a space between the sets of bars for each learner. As a suggestion, if using the graph paper provided here, in order to fit 10 learners along the x-axis it is best to make each bar 2 blocks wide (the smallest blocks), with 1 or 2 blocks in between each learner. If you have graph paper available, perhaps provide learners with a sheet to practice on and once they know how to draw their graph, they can copy it into the workbook here.

It is vitally important that learners report their actual findings. If they do not come up with results that agree with what they are expecting to find, it is FAR better that they report what they found than that they "tweak" their results or try to alter their discussion or hypothesis to fit in with what is expected. Full credit and praise should be given to an investigation that was carried out well and truthfully reported, rather than one in which certain information or findings are made up or changed. If students know what they were expecting, and think that there is something wrong with their results they should be encouraged to make suggestions about why they didn't see what they were expecting to see in the discussion section that follows.

The learners may also notice a trend in the resting heart rates of the members of their group that were recorded in the three days prior to this activity, and they are welcome to hypothesize and make observations. They are likely to notice for example, that the fittest members had the lowest resting heart rates.

Assess whether learners have adequately discussed their results. As previously mentioned, their actual results may not agree with what they should find. In this case they still deserve full credit for their observations. However they also need to show that they know what should have happened, based on their research around the topic. They should point out that fitter individuals have a stronger heart compared to unfit individuals. Like all muscles, the heart becomes stronger as a result of exercise, therefore, it can pump more blood through the body with every beat. As a result, during exercise, a fit heart does not need to pump as fast to deliver the same amount of blood that an unfit heart would, and it does so with less strain. Assess whether learners have pointed out any shortcomings in their investigation and if they have made suggestions. Learners should also discuss some of the benefits of exercise for the cardiovascular system, such as decreasing the risk of heart attack and other heart diseases.