1) The document discusses respiration in different organisms - earthworms, frogs, fish, insects, and plants. 2) In earthworms, gas exchange occurs through their thin, moist skin. Frogs can breathe through lungs or skin. Fish breathe through gills in their gills to absorb oxygen from water. Insects breathe through openings called spiracles connected to tracheae. 3) In plants, respiration occurs in leaves through stomata and in roots through root hairs, with oxygen and carbon dioxide diffusing in and out.

1. St. Vincent Pallotti School, Besa
Ls. 10 – Respiration in Organisms
Class : VII
Subject : Science
Part : IV

2. In Part IV, you will learn about –
 Breathing and Respiration in other animals
 Respiration in plants

3. Breathing in Earthworm
• The earthworm breathes through its skin.
• The skin of earthworm is quite thin and
moist.
• Gases can easily pass through the skin of
earthworm.
• The carbon dioxide produced during respiration is carried back by the blood. This carbon
dioxide is expelled from the body of the earthworm through its skin. Thus, in earthworm the
exchange of gases takes place through the thin and moist skin.
• So, the earthworm absorbs the oxygen (of air) needed for respiration through its thin and moist
skin. This oxygen is then transported to all the cells of the earthworm by its blood where it is
used in respiration (production of energy).

4. Frogs live on land as well as in
water. Though frogs have lungs
for breathing, they can also
breathe through their moist skin.
Thus, frog is an animal which
can breathe through lungs as
well as its moist skin.
The frog breathes through the lungs as well as
through skin.

5. Breathing in Fish
• The fish breathes by taking in water through its mouth
and sending it over the gills.
• When water passes over the gills, the gills absorb the
dissolved oxygen from this water.
Fish lives in water. The fish has special organs of breathing called 'gills'. The gills help the fish
to use oxygen which is dissolved in water (in which it lives). The gills are covered by gill
covers so they are not visible from outside.
• The extracted oxygen is absorbed by the blood and carried to all the parts of the fish for
respiration (release of energy. The carbon dioxide produced during respiration is brought
back by the blood into the gills for expelling int the surrounding water.
Gills
This happens as follows:

6. Breathing in Insects
• Air (rich in oxygen) enters into the insect through spiracles by the up and down
movements of its body.
• This air goes into the network of thin air-tubes called tracheae. From the tracheae, oxygen
of air diffuses into the body tissues of insect and reaches each and every cell of its body
where it is utilised in respiration (production of energy).
• Carbon dioxide produced during respiration in the cells diffuses into tracheae and carried
to the spiracles where it is expelled in the process of breathing. Thus, in insects the
exchange of gases occurs through tracheae.
All the insects have tiny holes on the sides of their
body which are called spiracles. The spiracles on
the body of insects are connected to a network of
thin air-tubes called tracheae which spread into the
whole body of the insect. The breathing in all the
insects takes place through spiracles and tracheae.
This happens as follows:

7. Respiration in Plants
The plants get energy by the process
of respiration in which food breaks
down in the presence of oxygen to
form carbon dioxide and water with
the release of energy. This energy is
used by the plant for carrying out its
various life processes.
Respiration in plants is carried out
by leaves and roots independently.

8. Respiration in Leaves
The leaves of plants have tiny pores on their surface which are called stomata. The exchange
of gases (oxygen and carbon dioxide) the leaves during respiration takes place through
stomata.
• Oxygen from air enters into a leaf
through stomata and reaches in all the
cells by the process of diffusion.
• This oxygen is used in respiration in
the cells of the leaf.
• The carbon dioxide produced during
respiration diffuses out from the leaf
into air through the same stomata.
This happens as follows:

9. Respiration in Roots
The roots of a plant are under the ground but root cells also need oxygen. The roots obtain
oxygen for breathing and respiration from the soil as follows:
• Air is present in-between the particles of soil. The roots of a
plant take up air from the spaces between the soil particles.
• The roots of a plant have a very large number of tiny hair on
them which are called 'root hair'. The root hair are in contact
with the air in the soil particles.
• Oxygen from air in soil particles diffuses into root hair and
reaches all the cells of the root where it is utilised in respiration.
• Carbon dioxide produced in the cells of the root during
respiration goes out through the same root hair by the process
of diffusion.
• Thus, the respiration in roots occurs by the exchange of gases
(oxygen and carbon dioxide) through the root hair.

10. Think and Answer
Three test-tubes are taken and labelled A, B and C. Each test-tube is half filled with
water.
(a) In test-tube A, a snail is kept.
(b) In test-tube B, a water plant is kept and
(c) In test-tube C, a snail and a water plant, both are kept.
The three test-tubes are then placed in sunlight. Which test-tube would have the highest
concentration of carbon dioxide ? Why?