1. Respiration -
ü It is the process that consumes stored energy from living body.
ü In this process exchange of gases takes place.
ü It is an example of anabolic process.
ü As result a gas-protein complex is formed. Example - hemoglobin in humans.
ü The process of breakdown of food in the cell with the release of energy is called cellular respiration.
ü Cellular respiration takes place in the cells of all organisms.
Aerobic respiration | Anaerobic respiration |
It occurs in the presence of oxygen. | It takes place in the absence of oxygen. |
The complete breakdown of food takes place in aerobic respiration. | Partial breakdown of food occurs in anaerobic respiration. |
End products of aerobic respiration are CO2 and water. | End products of anaerobic respiration are alcohol and CO2 or lactic acid (in muscles). |
A large amount of energy is produced during aerobic respiration. | Less amount of energy is produced during anaerobic respiration. |
Table 01- Types of respiration
NOTE: Anaerobic Respiration in Muscles -
ü Aerobic respiration takes place in humans, but under certain conditions, anaerobic respiration may also occur in our muscles for a short time, due to temporary deficiency of oxygen.
ü When we perform a heavy exercise like running, cycling, walking, weight lifting, etc., we require a large amount of energy.
ü To meet the energy requirement our muscle cells perform anaerobic respiration.
ü During this process, the glucose or food in the muscle cells is partially broken down in the absence of oxygen to form lactic acid and some extra energy is released.
ü This ours because during vigorous physical activity, the utilization of oxygen ours at a faster rate in the muscles that can be supplied by the blood.
ü When the lactic acid produced during anaerobic respiration, gets accumulated in the muscles, it causes muscle cramps.
ü The muscle cramps can be relieved by taking a hot water bath or a massage. This improves the circulation of blood and oxygen supply to the muscle cells increases.
ü The increased supply of oxygen results in the complete breakdown of lactic acid into carbon dioxide and water, thereby giving relief from cramps.
2. Breathing -
ü It is the process in which air rich in oxygen is taken inside and air rich in CO2 is given out, with the help of respiratory organs. Thus, breathing involves two steps which take place alternately.
ü Inhalation: Taking in of air rich in oxygen into our body is called inhalation.
ü Exhalation: Giving out air rich in carbon dioxide from our body to the external environment is called exhalation
(a) Mechanism of Breathing -
ü We take in air through our nostrils. When we inhale air, it passes through our nostrils into the nasal cavity.
ü From the nasal cavity, the air reaches our lungs through the windpipe.
ü Lungs are present in the chest cavity. This cavity is surrounded by ribs on the sides.
ü A large, muscular sheet called diaphragm forms the floor of the chest cavity.
Figure 01- Human lungs
Figure 02- Inhalation and exhalation
(b) Breathing In or Inhalation
ü When we breath air in (or inhale) two processes occur together, i.e. the muscles between the ribs contract causing the ribcage to move upward and outward, while the diaphragm contracts and moves downwards.
ü This upward and downward movement of ribcage and diaphragm respectively increases the space in the chest cavity and makes it larger.
ü As the chest cavity becomes larger, it sucks air from outside the lungs and lungs get filled up with air and expand.
(c) Breathing Out or Exhalation
ü When we breath air out or exhale the reverse process takes place, i.e. the muscles of the ribs release causing the ribcage to move downward and inward, while diaphragm releases and moves upward.
ü This downward movement of the rib cage and upward movement of diaphragm decreases the space in our chest cavity and makes it smaller.
ü When the chest cavity becomes smaller, the air is pushed out of the lungs.
Percentage of O2 | Percentage of CO2 | |
Inhaled air | 21% | 0.04% |
Exhaled air | 16.4% | 4.4% |
Table 02- Gas composition in breathing
3. Respiration in Plants-
(a) Respiration Through Leaves- The leaves of the plants have tiny pores on their surface which are called stomata. The exchange of gases, i.e. O2 and CO2 in the leaves takes place through stomata during respiration. The oxygen from air enters into a leaf through stomata and reaches inside all the cells of the leaf through diffusion while CO2 produced during respiration also diffuses from the leaf to the atmosphere through the stomata.
(b) Respiration Through Roots- Root cells of the plants respire under the ground. They also need oxygen to carry out respiration and releases energy for their own use. Root cells get oxygen from the air present in the spaces between the soil particles. Plant roots have a large number of tiny hairs on them which are called root hairs. Oxygen from the air present in soil particles diffuses into root hair and reaches to the cells of the root where it is utilize for respiration.
Figure 03- Respiration through leaves
4. Photosynthesis-
ü The exchange of gases takes place in the plants all the time, but it is increased during day time.
ü The leaves are more actively involved in photosynthesis during the day time in the presence of sunlight.
ü The CO2 released during respiration is utilized by the plant during photosynthesis to produce its food.
ü During photosynthesis, the O2 is released by plants which are taken up during respiration in plants. Therefore, a balance between CO2 and O2 is maintained by the plants.
ü Respiration thus provides continuous energy to plants to perform all its functions regardless of time.
Figure 04- Photosynthesis
5. Respiration Through Gills-
ü Fishes are the aquatic animals that live in water.
ü These have a special organ for breathing called gills.
ü The oxygen dissolved in water enters through the gills.
ü Gills are actually the projections of skin and have blood vessels for the exchange of respiratory gases.
ü The fishes breathe by taking in water through its mouth and sending it over the gills.
ü The oxygen dissolved in the water is extracted by the gills and the extracted oxygen is absorbed by the blood.
ü This oxygen is then carried to all the parts of fishes for respiration. The carbon dioxide produced during respiration is brought back by the blood into the gills and expelled into the surrounding water.
Figure 05- Gills of fish
NCERT PRACTICE QUESTIONS
1. Why does an athlete breathe faster and deeper than usual after finishing the race?
Ans.- Athletes need a lot of energy during the race, and for the release of energy, they need a lot of oxygen, therefore they breathe faster than usual after finishing the race so that demand of extra oxygen can be fulfilled.
2. List the similarities and differences between aerobic and anaerobic respiration.
Ans.- Similarity- In both kinds of respiration, anabolic pathway occur.
Differences
Aerobic respiration | Anaerobic respiration |
Takes place in the presence of Oxygen | Takes place in the absence of Oxygen |
End products are CO2 and H2O | End products are CO2 and alcohol |
Produces a large amount of energy | The energy released is less when compared to aerobic respiration |
It occurs in most plants and animals | Occurs in yeast and some bacteria |
3. Why do we often sneeze when we inhale a lot of dust-laden air?
Ans.- When we inhale dust containing air, the dust irritates the nose and as a reflexive action, dust is thrown out of nose through sneezing.
4. Take three test-tubes. Fill ¾th of each with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO2 ?
Ans.- Test tube A will have the highest concentration of CO2 because test-tube A will have Snail which expels out CO2 into the tube. In tube C, there is a plant which will inhale CO2 to decrease CO2 concentration in the tube C.
5. Tick the correct answer:
(a) In cockroaches, air enters the body through
(i) lungs (ii) gills (iii) spiracles (iv) skin
(b) During heavy exercise, we get cramps in the legs due to the accumulation of
(i) carbon dioxide (ii) lactic acid (iii) alcohol (iv) water
(c) Normal range of breathing rate per minute in an average adult person at rest is:
(i) 9–12 (ii) 15–18 (iii) 21–24 (iv) 30–33
(d) During exhalation, the ribs
(i) move outwards (ii) move downwards (iii) move upwards (iv) do not move at all
Ans.- a) (iii) spiracles b) (ii) lactic acid c) (ii) 15–18 d) (ii) move downwards
6. Match the items in Column I with those in Column II:
Ans.-
Column I | Column II |
(a) Yeast | (iii) Alcohol |
(b) Diaphragm | (iv) Chest cavity |
(c) Skin | (i) Earthworm |
(d) Leaves | (v) Stomata |
(e) Fish | (ii) Gills |
(f) Frog | (vi) Lungs and skin |
7. Mark ‘T’ if the statement is true and ‘F’ if it is false:
(i) During heavy exercise the breathing rate of a person slows down. (T/F)
(ii) Plants carry out photosynthesis only during the day and respiration only at night. (T/F)
(iii) Frogs breathe through their skins as well as their lungs. (T/F)
(iv) The fishes have lungs for respiration. (T/F)
(v) The size of the chest cavity increases during inhalation. (T/F)
Ans.- i) False ii) False iii) True iv) False v) True
8. Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction — upwards, downwards, or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.
(i) The air tubes of insects
(ii) Skeletal structures surrounding chest cavity
(iii) Muscular floor of chest cavity
(iv) Tiny pores on the surface of leaf
(v) Small openings on the sides of the body of an insect
(vi) The respiratory organs of human beings
(vii) The openings through which we inhale
(viii) An anaerobic organism
(ix) An organism with tracheal system
Ans.- (i) Trachea (ii) Ribs (iii) Diaphragm (iv) Stomata (v) Spiracles (vi) Lungs (vii) Nostrils
(viii) Yeast (ix) Ant
9. The mountaineers carry oxygen with them because-
(a) At an altitude of more than 5 km there is no air.
(b) The amount of air available to a person is less than that available on the ground.
(c) The temperature of air is higher than that on the ground.
(d) The pressure of air is higher than that on the ground.
Ans.- (b). The amount of air available to a person is less than that available on the ground.
Junior Science Topic - Respiration In Organism. Chapter notes, video lectures, power point presentation and NCERT exercise solution. (Class 7, CBSE syllabus, chapter 10)
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