-> The diffusion of gases from higher concentration area to
lower concentration area especially the exchange of Oxygen
and CO2 between an organism and its environment.
In plants, gaseous exchange takes place during
photosynthesis and respiration but In animals, gases are
exchanged during respiration.
The exchange of gases takes place in the plants through the tiny
pores of leaves called stomata. It also occurs in the roots of
the plant. They require oxygen for respiration and CO2 for
photosynthesis. CO2 produced during respiration move
outside
the root hair in the same way as oxygen do.
Net gaseous exchange
Also, CO2 is taken from the air which is used in the process of
photosynthesis by leaves. Even more, CO2 is produced during
respiration.
Thus,
Net gaseous exchange during daytime is
-> Oxygen diffuses out & CO2 diffuse in
At night, no photosynthesis process occurs and hence no
oxygen is produced. Oxygen from air diffuses into leaves and
carries out the respiration process.
As the result, CO2 is produced which diffuses out into the air.
Thus,
Net gaseous exchange during night time is
-> Oxygen diffuses in, CO2 diffuses out
Respiration in Animals
* Different animals have different modes of respiration.
for example:-
| Animals | Respiratory Organ |
|---|---|
| * Unicellular organisms like Amoeba, Paramecium, etc. | Cell membrane |
| * Earthworms | Skin |
| * Fishes | GIlls |
| * Grasshopper, Cockroach, Ants, etc. | Spiracles & Tracheae |
| * Human beings, Birds | Lungs |
* Respiratory organs have three common
features:-
(i) Large surface area- For the greater rate of diffusion of
respiratory gases
(ii) Thin permeable walls or surface- To ensure easy diffusion
and exchange of gases
(iii) Extensive blood supply- Respiratory organs like gills, lungs
have a rich blood supply for transporting respiratory gases.
* Respiratory Surface- The surface through which
gaseous exchange takes place is called the respiratory surface.
e.g. Lungs, Gills, Tracheae, etc.
Characteristics of the respiratory surface
(i) It should be permeable two gases.
(ii) It should be thin.
(iii) The surface area should be large.
(iv) It should be placed inside the body and well protected.
Q) Why the rate of breathing in an aquatic
organisms is much faster than terrestrial
organism?
Ans- As we know that terrestrial animals can breathe
oxygen in the atmosphere but aquatic animals need to use
the oxygen which dissolved in water. Since the amount of
oxygen dissolved in water is low as compared to the amount of
oxygen present in the air. So, aquatic organisms have to breathe quickly to maintain their respiratory process. Due to this, the breathing rate of
aquatic Organisms is much faster than terrestrial Organisms.
Respiration in Amoeba
-> Amoeba is a single-celled or unicellular organism and they have
not specific respiratory organ so the exchange of gases
happens to the surface of their body.
* Other examples who use the same process are paramoecium,
hydra etc.
Respiration in insects(Ants)
-> Ants have a pair of holes which present at both sides of the head
and those holes are called spiracles. Air enters inside the ant’s
body through spiracles and it opens into the tracheae. trachea and
tracheoles deliver oxygen directly into air sacs and tissue
cells and carry away carbon dioxide from the ant’s body. This
whole system is called the tracheal system.
Respiration in Earthworm
-> Earthworms don’t have lungs. They breathe through their
skin. Air enters through the skin by the process of diffusion and
moves into the whole body with the help of tiny capillaries. For
the process of diffusion, the earthworm's skin must be kept
moist. If worms dry out, they suffocate and gets ultimately
die. So, they survive only in water or damp places.
Respiration in Fishes
-> Fish respire through gills. Gills are a type of tissue made up of a feather-type structure called gills filaments. Gills filaments provide a large surface area for gaseous
exchange.
Fish take in oxygen which dissolves in water
through their mouth and reaches to gills. As water passes over
the gill filaments, Blood inside the capillaries picks up the
dissolved oxygen. The circulatory system then transports the
oxygen to all cells and tissues of the fishes’ body.
The CO2 then
released, removed from the body through their gills. The
water which enters in fishes exits through the openings in the
sides of the throat called the operculum.
Respiration in Frogs
-> Frogs are called amphibians, which means that they can live both
on land and in water. Frogs respire in many ways
because of their life cycle.
* From gills- Tadpoles use gills in order to respire
within their aquatic environment. Upon maturation from a
tadpole into a frog, these gills are lost.
* From skin- Frog respire through the skin when they live
in water. The skin of many frogs is thin which helps them to
allow for gaseous exchange.
* From lungs- Frog respire through lungs when they
live on land. Lungs help in gaseous exchange.
* From a lining along with the mouth- This type of
respiration can occur while the frog is not submerged in water.
-> The respiratory system consists of:-
Nose ⇾ Nasal cavity ⇾ Pharynx ⇾ Trachea ⇾ Bronchi ⇾ Lungs
⇙ ⇘
Bronchioles Alveoli
Note- Inhalation and Exhalation- Taking
oxygen from the air into the body during breathing called
inhalation and diffusion of CO2 in the atmosphere from our body
called exhalation.
-> One Breath means “one inhalation and one exhalation”.
Nostrils
-> The human respiratory system begins from the nose. The nose has two holes called nostrils. In Nostrils, fine hair is present
to filter the air taken in.
Nasal Cavity
-> The cavity or passage where the air reaches through
nostrils called nasal cavity or nasal passage. it is separated
from the mouth cavity
(buccal cavity or oral cavity) by a hard
bony palate so that we can breath air even when we are
eating food.
In the Nasal cavity, the Central septum divides the nostrils into two
pars i.e. left nostrils & right nostrils. It is also called Nasal
Septum.
Nasal passages are lined with ciliated epithelium and mucus.
Note- * Ciliated epithelium -> The epithelial tissue which is
lined with cilia is called the ciliated epithelium. they are fine hair-like structures present in Nasal Cavity.
Function:- They filter the large particles from the air.
* Mucus -> Slimy slippery substance which is lined with
cilia are called mucus.
Function:- It tries to make the air a little moist.
Overall, Air enters through nostrils, get warmed and moistened in
nasal cavity.
Pharynx
-> The part of the throat between the mouth and windpipe is called the pharynx.
It is also termed as a common passage for food and air.
From this place
-> Food goes to the Oesophagus.
-> Air goes to the trachea (windpipe).
Note- Trachea lies in front of oesophagus.
Q) How is it food does not enter in the trachea?
Ans-> Food does not enter in the tracheae because of
presence of epiglottis (a small flap of skin that acts as a
cover).
It prevents the food from entering the respiratory
tract. It is always locked.
if the food enters inside the trachea, then the
person may be die.
Trachea
-> Trachea is a tube which is commonly known as the windpipe.
The air passes from the pharynx to this pipe. It doesn’t collapse
even when there is no air passes through because of C-shaped
rings of soft bones called cartilage are present. Cartilage is
also called connective tissue.
Note- Bronchus ⇾ Singular
Bronchi ⇾ Plural
-> Trachea runs from the throat to the thoracic cavity.
Function:- The trachea help to pass the air from the pharynx to
Bronchi.
Thoracic Cavity
-> The cavity present between the Head and Abdomen is called the thoracic cavity. Organs that exist in this cavity are the lungs, heart, diaphragm, rib cage, etc.
Note- Diaphragm is the muscular structure
which denotes the end of
thoracic cavity.
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