Term 2, 2012
WOODLEIGH
SCHOOL
YEAR 8 – THE HUMAN BODY
PART B: RESPIRATION, TRANSPORTATION,
WASTE REMOVAL AND EXERCISE
Science Faculty
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TRANSPORTATION
Experiment: Water tracer
Aim: To show the pathway of water through stems and leaves.
Materials
• fresh stick of celery
• razor blade
• 2 beakers
• red and blue dye
• white tile
Safety
Razor blades are extremely sharp. Take special care.
Method
1. Set up the celery in beakers of dye as shown in the diagram.
2.
3.
Leave overnight.
Observe the celery stem and leaves next day. Note carefully the parts of the plant to which the dye has
moved.
4. Place the celery on the white tile and cut across the stem with a razor blade.
5. Make another cut lengthwise through the stem.
6. Look for the distribution of dye in the stem tissue.
Discussion
1. To which parts of the plant has the dye moved? Describe your observations of the leaf.
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2.
Make a large diagram of the cross-section of stem you cut. Use colours to indicate the distribution of
the dye. Compare it with the figure.
Evaluation
1. How clear was the pathway of dye in your celery?
2.
How could you have improved your experiment?
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Activity: Modelling xylem
The narrowness of xylem tubes is another factor that contributes to the movement of water upwards through
tall plants. You can demonstrate this using glassware of different diameters.
Materials
• 3 measuring cylinders: 1 large, 1 medium and 1 small
• 2 beakers
• a short length of glass or polythene tubing or a drinking straw
• a capillary tube
• water
Note: Capillary tubes resemble drinking straws, except that they are very fine and made of glass.
Method
1. Set up the three measuring cylinders. Half fill each with water. Carefully observe the edges of the
meniscus. What seems to be happening in each case?
2. Half fill the first beaker with water. Hold the glass tubing so that one end is immersed in the water.
Observe the level of water inside the tubing compared with the level of water in the beaker.
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3.
Half fill the second beaker with water. Hold a capillary tube vertically so that one end is immersed in
water. Observe the level of water inside the capillary tube compared with the level of water in the
beaker.
4. Compare the water level in each tube.
Results and Discussion
1. Look carefully at what is happening to the water level in each of the different diameter set-ups.
Outline your observations in each case.
2.
Write a brief statement outlining the relationship between the diameter of a tube and the distance
that water appears to be ‘dragged’ upwards inside the tube.
Conclusion
The effect you have observed is called ‘capillarity’. Find out what you can about how this process occurs.
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Experiment: Dissecting a sheep’s heart
Aim: To dissect a sheep’s heart to identify its main features.
Materials
• sheep’s heart
• scalpel
• dissecting board
• forceps
• newspaper
• disposable gloves
Safety
Scalpels are extremely sharp. Take special care.
Method
1. Lay a couple of sheets of newspaper on your dissecting board. Place the sheep’s heart on the board
facing you.
2. Use forceps to pull the muscle walls away so that you can see inside the heart chambers.
3. Try to locate the four chambers, heart valves and major blood vessels.
Discussion
1. Identify the four chambers and the major blood vessels of the heart.
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2.
The heart valves are like part of a parachute, with a fine film attached to the chamber walls by strong
stringy fibres. Suggest a role for the valves within the heart. (Hint: Work out which way the valves
open.)
Conclusion
1. Draw a diagram of your dissected sheep’s heart.
2.
Write a brief description of each structure you identify.
3.
The walls of the left side of the heart are much thicker and more muscular than the walls of the right
side of the heart.
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Activity: Looking at blood vessels
Look at some prepared microscope slides of arteries and veins. Note the thickness of the vessel walls and the
shape of the vessels.
Draw up a table of similarities and differences. Include labelled diagrams in your table.
Similarities
Differences
Diagrams
Experiment: The effect of exercise on heart rate
Aim: To investigate the effect of exercise on heart rate.
Materials
• stool
• watch with a second hand
• heart monitor and data logging equipment (optional)
Method
1. Locate your own pulse by finding the radial artery as shown in Figure 10.23. Now locate your partner’s
pulse.
2. Measure your partner’s resting heart rate by feeling their pulse. Record their heart rate in beats per
minute.
3. Ask your partner to walk on the spot steadily for 3 minutes.
4. Immediately after walking, measure your partner’s heart rate again. Record their heart rate in beats
per minute.
5. When your partner’s heart rate returns to normal, ask them to do some hard exercise for 3 minutes.
Stepping exercises are suitable, such as stepping up onto a stool and down again at a steady rate.
6. Immediately after the exercise, measure your partner’s heart rate every minute until it returns to the
normal resting rate. Record their heart rate in beats per minute for each minute.
7. Record your results in a table, spread sheet or graph.
Safety
Stop immediately if you have any breathing difficulties or feel unwell.
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Discussion
1. Why is it suggested that you don’t measure your own pulse?
2. What effect does each of the following have on your resting heart rate?
(a) Walking
(b) hard exercise
3. How do you explain any differences?
4. How long did it take your heart rate to return to its normal resting rate after hard exercise?
5. Outline how pulse rate can be used to indicate fitness.
SCIENCE IN ACTION: THAT CHEERFUL CHOCOLATELY FEELING
Eating a balanced diet seems to be one of the keys to staying healthy. Most of the time we try to eat sensibly.
But sometimes we want a treat. For many people, having a treat means having chocolate. This may not be as
bad for us as we might think.
The Swiss are the biggest chocolate consumers in the world, enjoying 10.1 kg per person a year (in 2000).
A recent Dutch survey found that Switzerland was the happiest country in the world. You have to wonder…
In 2000 the top five chocolate-consuming countries in the world were Switzerland, Austria (9.1 kg per person),
Ireland (8.8 kg per person), Germany (8.2 kg per person) and Norway (8.1 kg per person).The average
Australian eats about 7.5 kg per year.
Over the years, chocolate has developed a bad reputation. It has been associated with a number of evils such
as acne, tooth decay and migraine. Chocolate neither causes nor aggravates acne. Studies of students with mild
to moderate acne showed that eating chocolate had no effect on their acne condition. The sugar in chocolate
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does contribute to the development of cavities, but no more than sugar from other foods. Poor dental hygiene
is the primary cause of tooth decay. Chocolate may actually help to prevent cavities.
Cocoa butter, the main fat in chocolate, is solid at room temperature, but has a very low melting point.
Chocolate is one of the few foods that melt in your mouth. The cocoa butter coats the teeth and may protect
them from plaque formation.
For most migraine sufferers, chocolate can’t start the migraine chain reaction by itself. Numerous international
trials have found that other factors, such as stress (as a result of tiredness, excitement or anger) and hormones
need to be present at the same time. Fasting and eating some other foods may also play a role. More research
is needed before chocolate can be completely cleared, but the evidence so far seems promising for chocolate
lovers.
Chocolate may also help us to stay healthy. Cocoa beans are rich in antioxidants called flavonoids. Moderate
consumption of other flavonoid-containing foods such as red wine and tea is correlated with a reduction in
cardiovascular disease.
Recent research has turned up a chemical made in the brain and found in chocolate that may hold the key to
why we crave the sweet. It is called anandamide. The name comes from an ancient Indian word ananda,
meaning ‘bliss’. Anandamide relieves pain, helps us relax and generally improves our mood. Although the brain
makes anandamide, we don’t feel happy all the time because the chemical is broken down and inactivated very
quickly. But chocolate not only contains anandamide, it also contains substances that slow the chemical’s
breakdown, so we can enjoy its mood-improving effect longer.
Questions
1. How could eating chocolate help make Switzerland one of the happiest countries in the world?
2. Complete the following table:
Issue
Acne
Tooth decay
Migraine
Cardiovascular disease
Feelings
Cause or reason
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Effect of chocolate
Being Fit for Life
Eating a well-balanced diet is only part of being healthy. Many parts of our body also need exercise to work
efficiently.
Arteries are thick muscular blood vessels that carry blood away from the heart. The muscular walls are pushed
open by the blood being forced out of the heart. The arteries then narrow behind the blood helping to push it
along.
Veins are thinner blood vessels that carry blood to the heart. Valves help by only letting the blood flow towards
the heart. Veins need muscles to press against them to help the blood move. This happens when we walk or
run, so if you sit down all day it is not good for your veins. People who stand in one place for a long time
sometimes faint because the blood cannot get back to the heart quickly enough.
Capillaries are very small blood vessels that are very close to the cells in the body. Oxygen passes from the
capillaries into the cells and carbon dioxide passes from the cells into the capillaries. The capillaries also supply
the cells with nutrients such as glucose and remove wastes produced by active cells.
With regular exercise, over time more capillaries actually develop in muscle to provide for more efficient
oxygen delivery and waste removal. Exercise also helps our intestines to work more easily. Our muscles help to
move the food through our digestive system, just like with veins.
Our heart is a large and very special muscle. Like all muscles it benefits from regular exercise, becoming
stronger and working more easily. What does ‘being fit’ really mean? When you are fit your body can work at
its best. There is no one measure of being fi t because everyone is different. It is recommended that adults be
moderately active for about 30 minutes every day.
To do
Activity
Walking to school instead
of being driven in a car.
Eating three pieces of fruit
per day
Smoking
Eating take away food
every day
Eating ice cream every day
Going for a jog after school
Helps Fitness. Yes or No
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Reason
Eating different types of
food every day
Drinking lots of water
Drinking lots of soft drink
1. Look at all of the things listed in the table and write down if they help you stay fit or not.
2. Give a reason for your answer.
3. Add two more things to the table that help keep you fit.
4. Working with one or two partners, compare your answers. What is the best fitness strategy?
Activity: The air sacs in the lungs
The lungs are not simply two balloons that fill up with air. Inside the lungs are lots of tiny air sacs that look like
bunches of hollow grapes. Because there are so many sacs, they provide much more surface area than a single
large balloon would. This surface inside the lungs is where gases pass into and out of the bloodstream.
Materials
• ball of string
• 50 cm length of plastic tubing of at least 1 cm diameter
Method
1. Without twisting or folding the string, measure how much will fi t inside the plastic tubing.
2. Now twist and fold the string and measure how much will fi t inside the tubing.
Questions
1. Explain why folding increases the surface area.
2.
Explain why the lungs are not simply two big balloons.
3.
State where else you might find this folding inside the human body.
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Experiment: Tidal Volume
Aim: To make some observations about the effect of exercise on the tidal volume of humans.
Method
1. Collect three balloons.
2. Inflate each of them three times to about 30cm in diameter – this will stretch the balloon.
3. Label one balloon T1, the second T2 and the third T3
4. Take a normal breath and exhale normally into balloon t1.
5. Tie it off. This balloon measures your normal tidal volume.
6. Undertake 2 minutes of moderate exercise – say jogging on the spot.
7. Take balloon T2 and breathe out normally into the balloon.
8. Tie it off.
9. Undertake 2 minutes of heavy exercise – say running up and down stairs
10. Take balloon T3 and breathe normally into the balloon.
11. Tie it off.
12. Measure the diameter of the three balloons.
Materials
 3 round balloons
 1 measuring tape
Discussion
1. What do the terms vital capacity, tidal volume and residual volume mean?
2. Which of the balloons had the largest diameter?
3. From your data what effect would you say exercise has on tidal volume?
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4. Are the lungs ever completely empty?
Experiment: Kidney Dissection
Aim(s)
1. To identify the main structural parts of a kidney.
2. To observe and describe the microscopic structure of a kidney.
Method:
1. Collect a kidney and place it on your cutting board.
2. Examine the kidney – can you identify the three tubes entering and leaving the kidney?
3. Carefully using the scalpel cut the kidney in half long ways.
4. Draw a diagram of your kidney and identify the following parts
 Cortex
 Medulla
 Renal Pelvis
 Renal Vein
 Renal Artery
 Ureter
Discussion:
1. What is the purpose of the renal artery?
2. What is the purpose of the renal vein?
3. What is the purpose of the ureter?
4. What does the kidney do? Whereabouts does that happen?
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