7.5 Gaseous exchange in animals and plants 1 Gaseous exchange in animals and plants 7.57.57.57.5.

7.5 Gaseous exchange in animals and plants 1

Gaseous exchange in animals and plants

7.7.55


RespirationUnbreathed air

nitrogen (78%)

oxygen (21%) carbon dioxide

(0.03%)


RespirationBreathed air

nitrogen (78%)oxygen (21%)

carbon dioxide (0.03%)


RespirationBreathed airUnbreathed air

less oxygen

more carbon dioxide


Respiration

living cell

oxygen

break down food energy

support body activities


food + oxygen

carbon dioxide+ water + energy

Respiration

Word equation of respiration:


Gaseous exchange in animals

gaseous exchange (氣體交換 )

oxygen in aircarbon dioxide in air

taken inremove carbon dioxide from the body


Gaseous exchange in mealworms7.15 Experiment

video

1

mealworm

wire gauze

soda lime

capillary tube

colour marker

A

B


7.15a In what way is tube B different from

tube A?

There is no mealworm in tube B.

A

B


7.15b What is the purpose of setting up

tube B?

B

A

To eliminate the changes in the set-ups caused by changes in environmental factors, such as airtemperature and pressure.


2

A

B

Measure this distance

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


The mealworms take in ________and give out ______________. The ______________ is absorbed by soda lime.

oxygen

2 Try to explain the result in tube A.

carbon dioxidecarbon dioxide

7.15

7.5 Gaseous exchange in animals and plants

The gas pressure inside tube A therefore ___________ and becomes ___________ than the atmospheric pressure.

15

decreaseslower

7.15

As a result, the colour marker _____________________________is pushed towards the boiling

tube.


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. Thisaffects the experimental results.

7.15


The human respiratory system

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


Major parts of our respiratory system

7.16 3D model

Identify the major parts of the respiratory system.

Label the diagram.


nasal cavity

trachea

bronchus

bronchiole

7.16


air sac

intercostal muscle

rib

lung

diaphragm

7.16



nostrilsair

nasal cavity

trachea



bronchiair

bronchioles

air sacs



lungs are protected by the rib cage (肋骨籃 )



backbone

rib chest bone



diaphragm

intercostal muscles


Gaseous exchange in the air sac

3D animation


Gaseous exchange in the air sac

oxygen

carbon dioxide

direction of blood flow

capillary

air sac


The breathing mechanism

Do you know how breathing is brought about?


7.4Feeling your breath

Take a deep breath.

Feel the movement of your ribs.


7.4

They move upwards and outwards.

a Which way do your ribs move when you breathe in?


7.4b Which way do your ribs move when

you breathe out?

They move downwards and inwards.


The breathing mechanismMovements are brought by the actions of …

intercostal muscles

diaphragm


a Breathing in

intercostal muscles

diaphragm

lungrib


a Breathing in

1a Intercostal muscles contract.

Ribs move upwards and outwards. 1b Diaphragm

flattens.


a Breathing in

Gas pressure inside it decreases.

2 Volume of chest cavity

increases.


a Breathing in

3 Air is drawn in.


b Breathing out

1a Intercostal muscles relax.

Ribs move downwards and inwards.


b Breathing out

1b Diaphragm returns to dome shape.


b Breathing out

Gas pressure inside it increases.

2 Volume of chest cavity decreases.


b Breathing out

3 Air is forced out.


Using a model to show the action of the intercostal muscles during breathing

7.17 Animation

rib cage model (肋骨籃模型 )

rubber bandA

BC

B1


A

BC

B

Each part represents…

ribs

chest bonebackbone

intercostal muscles

17.17


2

F

G

D

H

E

Position X

I

measure this length

7.17


3

L

MJN

KO

measure this length

Position Y

7.17


4 Which rubber band, HI or NO, is shorter in length?

NO. H

I

N

O

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?

F

G

D

E

L

MJ

K

7.17


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

Position X Position Y

7.17


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

49

shortened

contracting

7.17


The ribs, move __________ and the chest volume __________. This is similar to the situation when we are breathing __________.

50

in

7.17

upwardsincreases


Using a model to show the action of the diaphragm during breathing

7.18 Animation

balloon-bell jar model

(氣球及鐘形罩模型 )

1 glass tube

Y-piece

balloons

rubber sheet


Each part represents…

52

1

trachea

bronchi

lungs

diaphragm

7.18


27.18


27.18


3 What happens to the balloons when the rubber sheet is pulled down?

The balloons become _______.bigger

7.18


When the rubber sheet is pulled down, the volume of the bell jar __________ and the gas pressure inside the bell jar becomes __________.

56

increases

lower

3

7.18


Therefore air flows ________ the balloons. This is similar to the situation when we are breathing ________.

57

in

3

7.18

into


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

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


This is similar to the situation when we are _____________.

60

4breathing out

7.18


In humans, gaseous exchange takes place in the ________.


air sacs



In humans, breathing is brought about by the actions of the _________________ between the ribs, and the ___________ that is located below the rib cage.

intercostal musclesdiaphragm


At the same time, the diaphragm becomes _________.

1 When we breathe in, the intercostal muscles _________.

The ribs move _________ and __________.

63

55

upwards

contract

outwards

flattened


These movements cause the volume of the chest cavity to

_________ and therefore the gaspressure inside it ___________. Air is then drawn into the lungs.

64

551

increasedecreases


lung

2 Which photo, A or B, was taken when the man was breathing out? Why?

65

55

A B

rib

heart

diaphragm

diaphragm is dome-shaped

Well done!


Gaseous exchange in plantsGreen plants

oxygen

carbon dioxide

Photosynthesis

take in

give out


Gaseous exchange in plantsGreen plantsRespiration

oxygen

carbon dioxide

take in

give outtake in

give out


Gaseous exchange in plantsGreen plants

oxygen and carbon dioxide: uptake or release?

In a day…


Gaseous exchange in plantsGreen plantsDepends on the rates

of photosynthesis and respiration


When do green plants take in and give out carbon dioxide?

7.19 Experiment video

hydrogencarbonate indicator


7.19

Concentration ofcarbon dioxide

> 0.03%~ 0.03%(normal

level in air)< 0.03%

Colour ofhydrogen-carbonateindicator

Yellow Red Purple


7.191

green leaves

aluminium foil

each tube contains 3 cm3 of hydrogencarbonate indicatorA B C D


a What is the purpose of setting up tube B?

A B C D

To make sure that the result in tube A is caused by the presence of the green leaf.

7.19


b What is the purpose of setting up tube D?

A B C D

To make sure that the result in tube C is caused by the presence of the green leaf.

7.19


2

A B C D

leave for one hour

7.19


2

A B C D

represent in the daytime

represent at night

7.19


Tube

Colour of the hydrogencarbonate indicator

At the beginning After one hour

A Red

B Red

C Red

D Red

3

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

7.19


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

Tube A Tube BThe green leaf takes in carbon dioxide from the air in the presence of light.

7.19


b Compare the results in tube C and tube D. What does the difference

show?

Tube C Tube D

7.19


b Compare the results in tube C and tube D. What does the difference

show?

Tube C Tube DThe green leaf gives out carbon dioxide in the dark.

7.19


Gaseous exchange in plants

In the daytimerate of

photosynthesis

rate of respiration

higher than

net uptake of carbon dioxide

net release of oxygen



At night

photosynthesis stops

respiration continues

net release of carbon dioxide

net uptake of oxygen


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




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


The balance of oxygen and carbon dioxide in nature

oxygen in air

carbon dioxide in air

photosynthesis of green plants

respiration of animals and plantstaken up

during

releases oxygen

releases carbon dioxide

taken up during


Living things carry out respiration. Green plants carry out photosynthesis.




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


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

atmosphereEarth

Sun

Animation


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.

2



3a Some heat energy is lost to space.

3a


The greenhouse effect3b Some heat energy is absorbed by

some gases in the atmosphere, leading to greenhouse effect.

3b



The burning of fossil fuels releases a lot of carbon dioxide.



amount of carbon dioxide absorbed during photosynthesis drops

large areas of forests are cleared


amount of carbon dioxide in the atmosphere increases



traps more heat and enhances greenhouse effect

average temperatures of the Earth keep increasing



traps more heat and enhances greenhouse effect

average temperatures of the Earth keep increasing

global warming (全球增温 )


Global warming

speeds up the melting of ice at polar regions


Global warming


living things at polar regions may lose their habitats


Global warming


sea level rises

flooding of low-lying areas


Global warming

causes climate changes

more frequent droughts and storms


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




The global temperatures continue to rise. This is known as global warming.


1 Which of the following leads to global warming?

105

A The atmospheric temperature rises continuously.

D The amount of carbon dioxide in the atmosphere increases.

C The amount of carbon dioxide in the atmosphere decreases.

B The amount of oxygen in the atmosphere decreases.

66


66

A An increase in the amount of oxygen in the atmosphere

D Flooding of low-lying areas

C Climate change

B Melting of ice capsExcellent!

2 Which of the following is not likely to be caused by global warming?

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