Unit: 1
Gaseous Exchange
Q 1: What is gaseous exchange ?
Ans: Gaseous exchange :
The process in which gases diffuse from an area of
higher contraction to an area of lower concentration to an area of lower con
centration is called Gaseous Exchange .
a) Gaseous exchange in Plants :
In plants gaseous exchange takes place during photo-
synthesis and respiration .
b) Gaseous exchange in Animals :
In animals gaseous exchange takes place during
respiration .
Q 2 : What is breathing ?
Ans : Breathing :
The process of inhalation and exhalation of air for the intake of oxy -
gen
and the giving out of Co2 is called Breathing .
Explanation :
The intake of oxygen is called inhalation and giving out of Co2 is called
exhalation . Breathing is the physical process in which animals move air into and out of
their body . It is done to get oxygen from air and to release Co2 in it .
Breathing Organs :
Plants are using stomata and lenticles for breathing .
2- Invertebrates are use trachea , book lungs and moist skin for breathing .
3-Vertebrates breaths through gills and lungs .
Q 3: Explain gaseous exchange in plants ?
Ans : Respiratory system in plants :
Introduction :
Unlike animals the plants do not have special respiratory organs such as
lungs or gills for the exchange of gases with environment . In plants gaseous ex-
change occurs through the surface . The outer surface of root , stem and leaves
is epidermis . This layer allows the exchange of gases between the inner cells and
environment.
Gaseous Exchange in Day time :
During the day both photosynthesis and respi-
ration occurs at the same time . Some of the oxygen produced during photosyn-
thesis and respiration occurs at the same time . Some of the oxygen produced
during photosynthesis is used up in respiration and the rest is released through
is not sufficient for photosynthesis therefore more co2 diffuses into the leaves
from surrounding air .
Gaseous Exchange in Night time :
During night time there is no photosynthesis in
Plants , So the leaf cells get oxygen from the environment for respiration and re-
leased co2 by diffusion
Gaseous Exchange in Plants :
a. In aquatic plants :
In aquatic plants the exchange of oxygen and co2 take place
By the process of diffusion in water . They have large number of stomata through
Which aquatic plants get dissolved oxygen from water .
b) In land plants :
The exchange of oxygen and co2 between land plants and their environ-
ment takes place with the help of following structure .
I. Stomata :
The stomata are small pores in epidermis of leaves and young stem .
Through stomata oxygen enters into the cellular spaces of the plant body and
Finally reaches the respiratory centers of the cell called mitochondria .
In mitochondria oxidation of food occurs and energy is released . Co2 produced
In this process diffuses out through stomata or may be utilized in the photosynthesis .
II. Lenticles :
In the stem of some nature woody plants , exchange of gases occurs
Through lenticels . Lenticels are airy aggregation of cells within the bark of
Stems and root of higher plants .
III. Root Hairs :
Roots obtain the dissolved oxygen from soil water for cellular respi-
ration through root hair by diffusion .
Q 3: How gaseous exchange occurs in humans ?
Ans : Human respiratory system :
A system of organs functioning in respiration is known
as respiratory system . It help in exchange of gases .
Explanation (Components ) :
Human respiratory system consists of air passage ways and
lungs .
Air passage ways :
The tube in which gases are passed toward lungs for exchange is
called air passage ways and lungs .
Parts of air passage ways :
The air passage ways consists of the following parts .
i. Nose :
The nose is only external part of the respiratory system which links the respira-
tory system which links the respiratory system with environment for exchange of respira-
tory gases .
Nostrils :
It is the opening of nose in which air enters to respiratory tract or tube .
Each nostril opens into cavities called Nasal cavity .
Function :
In nose the air is warmed , moistened and dust free by the hairs and
mucous membrane of nasal cavities .
ii. Pharynx :
The nasal cavities open into cone shaped muscular passage called pharynx .
It is also lined with mucous membrane . It is 4.5 inches long contains tonsils and
Adenoids which are organs and lymphatic tissue .
Function :
The mucus of pharynx moisturized the air , warm the air and trap dusts
and solid particles .
iii. Larynx :
It is a cartilages structure present on the upper end of trachea . It is also
lined with mucous membrane .
iv. Glottis :
The opening of larynx is known as glottis which is guarded by lid called epiglottis
The epiglottic prevents the entry of food or liquid into larynx .
Function :
1 : Larynx helps in filtration of air . 2: Larynx is also called sound box be-
cause it produce sound
v. Trachea :
It is tubular cartilaginous structure which is also called wind pipe , lies below the lar-
ynx . It is internally limned by ciliated epithelium which bears mucous secreting
cell . The trachea bear 16 to 20 c or horse shoe shaped cartilage rings which prevent
the trachea from collapsing and keep open .
Function :
1) The mucous and cilia of trachea , filter , moist and warmth the air .
2) Trachea provide a passage for air move toward lungs .
vi. Bronchi :
The trachea is divide into right and left bronchi which enters to each lungs
bronchi are cartilaginous air passage which limned with mucous membrane .
Function :
1: Bronchi divided the air for each lung. 2 : It also filter , moisturized and
warmth the air .
vii. Bronchioles :
The bronchi divided and redivided forming an air way network inside the
lungs called bronchioles . It lack cartilage lungs or plates but contain circular smooth
muscles and elastic fibbers .
Diameter :
The bronchioles are approximately 1mm or less in diameter .
Function :
The bronchioles are responsible for controlling air distribution in the lungs .
viii. Alveoli :
The bronchioles divide and subdivide and finally open into small collection
of air sac , where gases exchange occurs is called alveoli . On side of alveoli there is
dense network of blood capillaries which provides blood to alveoli for the exchange of
gases .
Function :
The alveoli are the functional units of lungs because gases exchange occurs
in alveoli .
ix. Lungs :
Human have two lungs which are located in the chest cavity . In the chest cavity
base of two lungs is present in diaphragm and the apexes of lungs is extended above
the first ribosome .
Membrane :
Each lung is surrounded by two tough flexible , transparent thin membrane
called plural membrane . It is filled with fluid which reduces friction between the lungs
and the wall of the thorax .
spongy in nature :
. The lungs are spongy because of the presence of millions of alveoli
Figure 1human lungs
Q 4: Describe the mechanism of breathing in human beings ?
Ans: Mechanism of breathing :
Definition :
It is the process in which the lungs expand to take in air them contact to
expel it .
Controlling center :
Breathing is involuntary process in which is controlled by medulla
obligate of brain .
Phases of breathing :
The cycle of breathing which occurs about 15 per minute ,
consisting of two phases .
Inspiration:
Definition:
The intake of air is called inspiration .
Mechanism :
1) During respiration the inter coastal muscles of ribs contract , resulting ribs and
sternum move upwards and outwards .
2) During inspiration the diaphragm muscles also contract , as a result the diaphragm
move downward and become dome shaped .
3) Due to the movements of ribs and diaphragm the volume and capacity of tho-
racic cavity increases in size and the pressure of air inside the chest cavity de-
creases .
4) Due to increase in the volume of chest cavity and the decrease of air pressure
of the lungs , the air rushes sucked from atmosphere into lungs .
Expiration :
Defination :
The taking out of air from lungs is called Expiration .
Mechanism :
During expiration the intercoastal muscles of ribs relax , resulting the ribs and sternum
move downwards and inwards .
