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

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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

mealworm

wire gauze

soda lime

capillary tube

colour marker

7.15a In what way is tube B different from

tube A?

There is no mealworm in tube B.

7.15b 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 airtemperature and pressure.

Measure this distance

Distance between the colour marker

and the stopper (cm)

At the beginning 20 minutes later

Discussion

1 Which tube contains less gas at the end of the experiment?

Tube A.

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

7.5 Gaseous exchange in animals and plants

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

decreaseslower

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

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.

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

air sac

intercostal muscle

diaphragm

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.

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

Each part represents…

chest bonebackbone

intercostal muscles

Position X

measure this length

Position Y

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

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

Position X Position Y

6 Which parallelogram, DEFG or JKLM, is larger in area?

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

Position X Position Y

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

shortened

contracting

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

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…

trachea

bronchi

diaphragm

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

The balloons become _______.bigger

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

increases

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

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

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.

This is similar to the situation when we are _____________.

4breathing out

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 __________.

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.

increasedecreases

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

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

Concentration ofcarbon dioxide

> 0.03%~ 0.03%(normal

level in air)< 0.03%

Colour ofhydrogen-carbonateindicator

Yellow Red Purple

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.

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.

A B C D

leave for one hour

A B C D

represent in the daytime

represent at night

Colour of the hydrogencarbonate indicator

At the beginning After one hour

Purple

Yellow

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

Tube A Tube B

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.

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

Tube C Tube D

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

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

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

Animation

The greenhouse effect

1 Sunlight passes through the atmosphere and reaches the Earth.

2 Heat energy is reflected back from the Earth’s surface.

3a Some heat energy is lost to space.

The greenhouse effect3b Some heat energy is absorbed by

some gases in the atmosphere, leading to greenhouse effect.

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?

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.

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?

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

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