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Gaseous Exchange in Plants:
Plants Have No organs or systems for exchange of Gases with the environment every
cell of the plant body exchange gases with the environment by its own
...
The gaseous
exchange occurs through these stomata
...
In young
stems and leaves,some gaseous exchnage also occurs through the cuticle which is
present over their epidermis|

Gaseous Exchange in a Leaf
leaf cells faces two situations
...
Similarly the carbon dioxide
produced during cellular respiration is utilized in photosynthesis
...

In woody steam and mature roots, the entire surface is covered by bark which is
impervious to gases or water
...

These are called the lenticels
...
|the lenticels
are slightly more raised than the general surface of stems|
Gases diffuse in and out of the general surface of the young roots
...

The aquatic plants get the oxygen dissolved in water and release carbon dioxide in
the water
...
They are the
passageways for gases and water vapours
...


Problems:
what is the net gaseous exchange from leaves during day and night times?

Apparatus Required:
Petri dish,water,glass slides and cover slips, methylene blue,light Microscope
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>The cells of leaves carry out photosynthesis during day time only
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Procedure:
1
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2
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3
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4
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5
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6
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Observation: observe both epidermis(upper and lower)and point out the
stomata
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draw
your observations on the notebook
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How many stomata did you observe?

II
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we can divide the respiratory system in two parts i
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the Air Passage Way:
The air passage way consists of the parts through which the outside air comes in the
lungs and after the exchange of gases it goes out
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the nose encloses the nasal cavity
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The nasal cavity is divided into two portions by a wall
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The mucous
also moistens and warm the incoming air and keep it temperature nearly equal to that
of the body
...
Pharynx is a muscular passage and is common to both food and air
...


Air Passage Way:
The air Goes from the pharynx into the larynx
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Analyzing and interpreting:
Identify the structure of human air passageway in charts and models
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The larynx is a box, made the cartilage
...
it is
also called the voice box
...
The
vocal cords vibrate when the air passes through them
...

|The vibrations in vocal cords and the movement of lips, cheeks ,tongue and jaws
produced specific sounds which result in speech
...
3)
Larynx continues to the Trachea, which is also called the windpipe
...
there are C-shaped cartilaagenous rings in the wall of trachea
...

On entering the chest cavity, the trachea divides into two smaller tubes called bronchi (singular:
bronchus)
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The bronchi continue dividing in the lungs until they make several fine tubes called bronchioles
...
The bronchioles end as fine
tubules called the alveolar ducts
...
The
alveoli from the respiratory surface in human body
...
it is bound on the outside by a network of capillaries
...
3)
|The trachea and the bronchi are also lined with ciliated and glandular cells
...
that have escaped
from the nasal cavity
...
|
The pulmonary artery from the heart containing deoxygenated blood enters the lungs and branches into
arterioles and then into capillaries which surround the alveoli
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The pulmonary vein carries
the oxygenated blood back to the heart
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There is a pair of lungs in
the thoracic cavity
...
A thick muscular structure,called
diaphragm, is present below the lungs
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They are spongy and elastic organs
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Each lung is enclosed by two membranes called the outer pleural
membrane and the inner pleural membrane
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The Mechanism Of Breathing
The physical movements associated with the gaseous exchange
are called breathing
...
e
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1
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at the same time the dome-shaped diaphragm
contracts and is lowered
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as a result, the lungs expand and their pressure
within them also decreases
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The Mechanism of Breathing
2
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The rib muscles relax bringing the
ribs back to the original position
...
This reduces the space in
the chest cavity and increases the pressure on lungs
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The Mechanism of Breathing
Human breathe 16-20 time per minute in normal circumstances
i
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The rate of breathing is controlled by the respiratory
centre in the brain
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|the breathing movements are involuntary to a large
extent
...
|

When we do exercise or some hard job our muscles cells carry
out cellular respiration at greater rate
...
This greater than normal concentration of corban
dioxide stimulates the respiratory centre of brain
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During exercise or other hard physical works the breathing Rate
may increase up to 30-40 times per minute
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04%
4%
Dioxide
Amount of Nitrogen 79%
79%
Amount of Water
Variable
saturated
vapours
Amount of dust
Variable
Almost None
particles
Temperature
Variable
Almost equal to
body temprature

A Model of the action of diaphragm:

Apparatus: A bell Jar Y shaped Glass tube two balloons rubber
sheet procedure
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>Tie a thin rubber sheet on the open end of the jar
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The rubber sheet acts as
the diaphragm and the balloon act as the lungs
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The
balloons get inflated
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>To demonstrate expiration, the rubber sheet is allowed to go
back to its original position
...
This
show how the lungs are deflated when the diaphragm comes
back to its original position

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