# Gaseous exchange in animals and plants

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Gaseous exchange in animals and plants
7.5

Respiration Unbreathed air nitrogen (78%) oxygen (21%)
carbon dioxide (0.03%)

Respiration Breathed air nitrogen (78%) oxygen (21%)
3 Respiration Breathed air nitrogen (78%) oxygen (21%) carbon dioxide (0.03%)

Respiration Unbreathed air Breathed air less oxygen
4 Respiration Unbreathed air Breathed air less oxygen more carbon dioxide

support body activities
Respiration energy break down food oxygen support body activities living cell

Respiration Word equation of respiration: food carbon dioxide + oxygen
+ water + energy

gaseous exchange (氣體交換)
Gaseous exchange in animals oxygen in air carbon dioxide in air remove carbon dioxide from the body taken in gaseous exchange (氣體交換)

7.15 Gaseous exchange in mealworms 1 wire gauze soda lime
Experiment video Gaseous exchange in mealworms 1 wire gauze soda lime capillary tube colour marker A mealworm B

7.15 a In what way is tube B different from tube A?
There is no mealworm in tube B. A B

7.15 b What is the purpose of setting up tube B?
To eliminate the changes in the set-ups caused by changes in environmental factors, such as air temperature and pressure. A B

11 7.15 2 Measure this distance A B

Distance between the colour marker
7.15 2 Tube Distance between the colour marker and the stopper (cm) At the beginning 20 minutes later A B

7.15 Discussion 1 Which tube contains less gas at the end of the experiment? Tube A.

7.15 2 Try to explain the result in tube A.
14 7.15 2 Try to explain the result in tube A. The mealworms take in ________ and give out ______________. The ______________ is absorbed by soda lime. oxygen carbon dioxide carbon dioxide

is pushed towards the boiling tube.
7.15 The gas pressure inside tube A therefore ___________ and becomes ___________ than the atmospheric pressure. decreases lower As a result, the colour marker _____________________________ is pushed towards the boiling tube.

7.15 3 We should not hold the boiling tubes with our hands during the experiment. Why? The heat energy from our hands will heat up the air inside the tubes and cause the air to expand. This affects the experimental results.

The human respiratory system
Humans and most animals have a respiratory system (呼吸系統) for gaseous exchange.

7.16 Major parts of our respiratory system
3D model Major parts of our respiratory system Identify the major parts of the respiratory system. Label the diagram.

19 7.16 nasal cavity trachea bronchus bronchiole

20 7.16 air sac rib intercostal muscle lung diaphragm

The human respiratory system
air nostrils nasal cavity trachea

The human respiratory system
22 The human respiratory system air bronchi bronchioles air sacs

lungs are protected by the rib cage (肋骨籃)
23 The human respiratory system lungs are protected by the rib cage (肋骨籃)

The human respiratory system
24 The human respiratory system backbone chest bone rib

The human respiratory system
25 The human respiratory system intercostal muscles diaphragm

Gaseous exchange in the air sac
3D animation

Gaseous exchange in the air sac
27 Gaseous exchange in the air sac carbon dioxide oxygen direction of blood flow air sac capillary

The breathing mechanism
Do you know how breathing is brought about?

7.4 Feeling your breath Take a deep breath.
Feel the movement of your ribs.

7.4 a Which way do your ribs move when you breathe in?
30 7.4 a Which way do your ribs move when you breathe in? They move upwards and outwards.

7.4 b Which way do your ribs move when you breathe out?
31 7.4 b Which way do your ribs move when you breathe out? They move downwards and inwards.

The breathing mechanism
32 The breathing mechanism Movements are brought by the actions of … intercostal muscles diaphragm

33 a Breathing in rib lung intercostal muscles diaphragm

a Breathing in 1a Intercostal muscles contract.
34 a Breathing in 1a Intercostal muscles contract. Ribs move upwards and outwards. 1b Diaphragm flattens.

a Breathing in Gas pressure inside it decreases.
35 a Breathing in Gas pressure inside it decreases. 2 Volume of chest cavity increases.

36 a Breathing in 3 Air is drawn in.

b Breathing out 1a Intercostal muscles relax.
37 b Breathing out 1a Intercostal muscles relax. Ribs move downwards and inwards.

38 b Breathing out 1b Diaphragm returns to dome shape.

b Breathing out 2 Volume of chest cavity decreases.
39 b Breathing out 2 Volume of chest cavity decreases. Gas pressure inside it increases.

40 b Breathing out 3 Air is forced out.

7.17 Animation Using a model to show the action of the intercostal muscles during breathing B 1 A rubber band rib cage model (肋骨籃模型) C B

7.17 1 Each part represents… ribs intercostal muscles chest bone
42 7.17 1 Each part represents… ribs B A intercostal muscles C B chest bone backbone

43 7.17 2 Position X H G measure this length D F E I

44 7.17 3 Position Y N J M measure this length K L O

7.17 4 Which rubber band, HI or NO, is shorter in length? NO. N H O I
45 7.17 4 Which rubber band, HI or NO, is shorter in length? NO. N H O I

46 7.17 5 In which case, position X or Y, are the intercostal muscles contracting? Position X Position Y

7.17 6 Which parallelogram, DEFG or JKLM, is larger in area? G J M D F
47 7.17 6 Which parallelogram, DEFG or JKLM, is larger in area? G J M D F K L E

7.17 7 In which case, position X or Y, is the chest volume greater?
48 7.17 7 In which case, position X or Y, is the chest volume greater? Position X Position Y

49 7.17 8 When the model is set from position X to position Y, the rubber band becomes ___________. This represents the intercostal muscles are ___________. shortened contracting

50 7.17 The ribs, move __________ and the chest volume __________. This is similar to the situation when we are breathing __________. upwards increases in

balloon-bell jar model
7.18 Animation Using a model to show the action of the diaphragm during breathing 1 glass tube balloon-bell jar model (氣球及鐘形罩模型) Y-piece balloons rubber sheet

52 7.18 Each part represents… 1 trachea bronchi lungs diaphragm

7.18 2

54 7.18 2

7.18 3 What happens to the balloons when the rubber sheet is pulled down? The balloons become _______. bigger

56 7.18 When the rubber sheet is pulled down, the volume of the bell jar __________ and the gas pressure inside the bell jar becomes __________. 3 increases lower

57 7.18 3 Therefore air flows ________ the balloons. This is similar to the situation when we are breathing ________. into in

7.18 4 What happens to the balloons when the rubber sheet is pushed up? The balloons become ________. smaller

59 7.18 4 When the rubber sheet is pushed up, _____________________________ _______________________________________________________________________________________ the volume of the bell jar decreases and the gas pressure inside the bell jar becomes higher. Therefore air flows out of the balloons.

7.18 4 This is similar to the situation when we are _____________.
60 7.18 4 This is similar to the situation when we are _____________. breathing out

Gaseous exchange in animals
In humans, gaseous exchange takes place in the ________. air sacs

Gaseous exchange in animals
62 Gaseous exchange in animals In humans, breathing is brought about by the actions of the _________________ between the ribs, and the ___________ that is located below the rib cage. intercostal muscles diaphragm

5 1 When we breathe in, the intercostal muscles _________. contract
The ribs move _________ and __________. upwards outwards At the same time, the diaphragm becomes _________. flattened

64 5 These movements cause the volume of the chest cavity to _________ and therefore the gas pressure inside it ___________. Air is then drawn into the lungs. 1 increase decreases

diaphragm is dome-shaped
5 Well done! 2 Which photo, A or B, was taken when the man was breathing out? Why? A B rib lung diaphragm is dome-shaped heart diaphragm

Gaseous exchange in plants
Photosynthesis Green plants give out oxygen carbon dioxide take in

Gaseous exchange in plants
67 Gaseous exchange in plants Respiration Green plants give out take in oxygen carbon dioxide give out take in

Gaseous exchange in plants
68 Gaseous exchange in plants In a day… Green plants oxygen and carbon dioxide: uptake or release?

Gaseous exchange in plants
69 Gaseous exchange in plants Depends on the rates of photosynthesis and respiration Green plants

7.19 When do green plants take in and give out carbon dioxide?
70 7.19 Experiment video When do green plants take in and give out carbon dioxide? hydrogencarbonate indicator

7.19 Concentration of carbon dioxide > 0.03% ~ 0.03%
(normal level in air) < 0.03% Colour of hydrogen-carbonate indicator Yellow Red Purple

7.19 1 green leaves aluminium foil
each tube contains 3 cm3 of hydrogencarbonate indicator A B C D

7.19 a What is the purpose of setting up tube B?
73 7.19 a What is the purpose of setting up tube B? To make sure that the result in tube A is caused by the presence of the green leaf. A B C D

7.19 b What is the purpose of setting up tube D?
74 7.19 b What is the purpose of setting up tube D? To make sure that the result in tube C is caused by the presence of the green leaf. A B C D

75 7.19 2 leave for one hour A B C D

76 7.19 2 represent in the daytime represent at night A B C D

hydrogencarbonate indicator
7.19 3 Tube Colour of the hydrogencarbonate indicator At the beginning After one hour A Red B C D Purple Red Yellow Red

7.19 4a Compare the results in tube A and tube B. What does the difference show? Tube A Tube B

79 7.19 4a Compare the results in tube A and tube B. What does the difference show? The green leaf takes in carbon dioxide from the air in the presence of light. Tube A Tube B

7.19 b Compare the results in tube C and tube D. What does the difference show? Tube C Tube D

81 7.19 b Compare the results in tube C and tube D. What does the difference show? The green leaf gives out carbon dioxide in the dark. Tube C Tube D

rate of photosynthesis
82 Gaseous exchange in plants In the daytime rate of photosynthesis net release of oxygen higher than rate of respiration net uptake of carbon dioxide

Gaseous exchange in plants
83 Gaseous exchange in plants At night photosynthesis stops net release of carbon dioxide respiration continues net uptake of oxygen

Gaseous exchange in plants
In the daytime, there is a net release of oxygen and a net uptake of carbon dioxide in green plants.

Gaseous exchange in plants
85 Gaseous exchange in plants At night, green plants take in oxygen and give out carbon dioxide.

The balance of oxygen and carbon dioxide in nature
86 The balance of oxygen and carbon dioxide in nature oxygen in air releases oxygen taken up during respiration of animals and plants photosynthesis of green plants releases carbon dioxide taken up during carbon dioxide in air

The balance of oxygen and carbon dioxide in nature
Living things carry out respiration. Green plants carry out photosynthesis.

The balance of oxygen and carbon dioxide in nature
88 The balance of oxygen and carbon dioxide in nature The two processes help keep a balance of oxygen and carbon dioxide in nature.

89 The effect of the increasing amount of carbon dioxide in the atmosphere on us Animation Sun atmosphere Earth

The greenhouse effect 1 Sunlight passes through the atmosphere and reaches the Earth. 1

2 Heat energy is reflected back from the Earth’s surface.
91 The greenhouse effect 2 Heat energy is reflected back from the Earth’s surface. 2

3a Some heat energy is lost to space.
92 The greenhouse effect 3a Some heat energy is lost to space. 3a

The greenhouse effect 3b
93 The greenhouse effect 3b Some heat energy is absorbed by some gases in the atmosphere, leading to greenhouse effect. 3b

The effect of the increasing amount of carbon dioxide in the atmosphere on us
The burning of fossil fuels releases a lot of carbon dioxide.

The effect of the increasing amount of carbon dioxide in the atmosphere on us
large areas of forests are cleared amount of carbon dioxide absorbed during photosynthesis drops

amount of carbon dioxide in the atmosphere increases

amount of carbon dioxide in the atmosphere increases
97 amount of carbon dioxide in the atmosphere increases traps more heat and enhances greenhouse effect average temperatures of the Earth keep increasing

98 amount of carbon dioxide in the atmosphere increases global warming (全球增温) traps more heat and enhances greenhouse effect average temperatures of the Earth keep increasing

Global warming speeds up the melting of ice at polar regions

speeds up the melting of ice at polar regions
100 Global warming speeds up the melting of ice at polar regions living things at polar regions may lose their habitats

speeds up the melting of ice at polar regions
101 Global warming speeds up the melting of ice at polar regions sea level rises flooding of low-lying areas

causes climate changes
102 Global warming causes climate changes more frequent droughts and storms

The effect of the increasing amount of carbon dioxide in the atmosphere on us
The increasing amount of carbon dioxide in the atmosphere enhances the greenhouse effect.

104 The effect of the increasing amount of carbon dioxide in the atmosphere on us The global temperatures continue to rise. This is known as global warming.

6 1 Which of the following leads to global warming?
A The atmospheric temperature rises continuously. B The amount of oxygen in the atmosphere decreases. C The amount of carbon dioxide in the atmosphere decreases. D The amount of carbon dioxide in the atmosphere increases.

6 2 Which of the following is not likely to be caused by global warming? A An increase in the amount of oxygen in the atmosphere B Melting of ice caps Excellent! C Climate change D Flooding of low-lying areas