Tuesday 21 August 2012

CBSE Class 7 Science - CH10 - Respiration in Organisms (#eduvictors)(#class7Science)

Respiration in Organisms

NCERT Chapter Solutions and other Q & A

Q1: How breathing is different from respiration?

1It involves the intake of oxygen and release of Carbon dioxide.Respiration is more complex and it includes
breathing as well as oxidation of food in cells to release energy.
2It is a physical process i.e. exchange of gases.It is a biochemical process in which food is broken along with the release of energy.
3It involves breathing organs e.g. lungs in mammals.It occurs at a cellular level

Q2(NCERT): Why does an athlete breathe faster and deeper than usual after finishing the race?

Answer: Our body needs energy for all activities. While doing heavy exercises like running, there is a larger demand for energy to perform those activities. Hence more oxygen is required to meet the extra demand for energy. Therefore an athlete breathes faster and deeper than usual after finishing the race.

Also during running, due to lack of oxygen, some muscles may respire anaerobically and form lactic acid. Extra oxygen is also required to burn this lactic acid into carbon dioxide.

Q3: Rearrange the following parts of the Respiratory system in order.       Trachea, nose, alveoli, bronchi, nasal cavity, bronchiole.

       Nose → Nasal Cavity → Trachea → Bronchi → Bronchiole → Alveoli

Q4: What are different types of respiration

Answer: Two types:
  • Aerobic respiration
  • Anaerobic respiration

Q5(NCERT): List the similarities and differences between aerobic and anaerobic respiration. 

1It uses oxygen in the process.Anaerobic respiration takes place in the absence of oxygen.
2In this process, glucose is completely broken down into CO2, Water along with the release of energy.In this process, glucose is broken into ethyl alcohol, CO2 and energy.
3It occurs in all organisms like mammals.It usually occurs in lower organisms like yeast (fungi) and bacteria.  It can occur muscles of higher organisms during heavy activities.
4Glucose + Oxygen → Carbon dioxide + Water + EnergyGlucose → Ethyl alcohol + Carbon dioxide + Energy

Q6: Why yeast is used in the winemaking industry?

Answer: Yeast is a type of fungi which respires anaerobically and produce alcohol. Therefore, they are used to make wine and beer.

Q7(NCERT): Why do we often sneeze when we inhale a lot of dust-laden air?

Answer: When we inhale dust-laden air, dirt particles are captured within the nostrils. Sometimes they get past the nostril hair in the nasal cavity and irritate the lining of the cavity. As a result, we sneeze. Sneezing expels these foreign particles from the inhaled air and a dustfree, clean air enters our body.

Q8(NCERT): 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?


Test tube A will have the highest concentration of CO2. The experiment shows the relationship between plants and animals. During breathing, snail inhales dissolved oxygen from water and releases carbon dioxide(CO2). Water-plant along with respiration performs another important function called photosynthesis. During photosynthesis, water-plant absorbs CO2, prepares food and releases oxygen. Therefore, Tube B and C have less amount of CO2concentration as compared to test tube A.

Q9(NCERT): Tick the correct answer:
(a) In cockroaches, air enters the body through(i) lungs
(ii) gills
(iii) spiracles
(iv) skin

Answer:  (iii) spiracles

(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

Answer:  (ii) lactic acid

(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

Answer:  (ii) 15–18

(d) During exhalation, the ribs(i) move outwards
(ii) move downwards
(iii) move upwards
(iv) do not move at all

Answer:  (ii) (ii) move downwards (and inwards)

Q10: Name the two steps in breathing.

Answer: Breathing involves intake of oxygen-rich air and out-take of CO2-rich air. The two steps involved are:
  1. Inhalation
  2. Exhalation

Q11(NCERT): Match the items in Column I with those in Column II:

Column I                   Column II
a. Yeast(i) Earthworm
b. Diaphragm(ii) Gills.
c. Skin (iii) Alcohol
d. Leaves (iv) Chest cavity
e. Fish(v) Stomata
f. Frog(vi) Lungs and skin
g. insects(vii) Tracheae


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
g. insects(vii) Tracheae

Q12(NCERT): 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)

(i) During heavy exercise the breathing rate of a person slows down. (False ✗)
Explanation: During heavy exercise, more oxygen is required to meet extra demand of energy. Therefore breathing rate increases.

(ii) Plants carry out photosynthesis only during the day and respiration only at night. (False ✗)
Explanation:  Photosynthesis occurs in the presence of sunlight. Respiration is a continuous process and occurs all the time (day and night).

(iii) Frogs breathe through their skins as well as their lungs. (True ✓)

(iv) The fishes have lungs for respiration. (False ✗)
Explanation:  Fishes breathe through gills.

(v) The size of the chest cavity increases during inhalation. (True ✓)

Q13(NCERT):  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 the chest cavity
(iii) Muscular floor of the 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 a tracheal system


(i) Trachea
(ii) Ribs
(iii) Diaphragm
(iv) Stomata
(v) Spiracles
(vi) Lungs
(vii) Nostrils
(ix) Ant

Q14(NCERT): 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 the air is higher than that on the ground.
(d) The pressure of air is higher than that on the ground.

Answer: (b) The amount of air available to a person is less than that available on the ground.

Q15: Answer the following:
(a) When does a person need artificial respiration?
(b) From where can the person get a supply of oxygen for artificial respiration?
(c) Does the person need to be kept on artificial respiration temporarily or permanently?

Answer: (a) During emergency conditions (e.g. fatal accidents, lungs failure etc.), lungs do not work properly, artificial respiration is required.

(b) The person gets oxygen though an instrument called ventilator which act as artificial lungs. 

(c) The person is kept on artificial respiration temporarily. When a person regains his health and starts breathing naturally, artificial respiration is no longer required.

Q16: Name the animal who does dual breathing?

Answer: Frogs. Inside water, they breathe through their skin. When on land, they breathe through lungs.

Q17: How does plant respire?

Answer: Plant respires through the following ways
  1. Through stomata present in leaves.
  2. Through lenticels present on the bark of the stem
  3. Through root hairs which takes up air via spaces present between the soil particles.

Q18: How does breathing take place in fishes?

Answer: Fish respire through their gills. Dissolved air in the water is taken in by the gills and is supplied to blood capillaries where the exchange of gases takes place.

Q19: What are the functions of ribs and diaphragm during breathing? Describe their functioning.

Answer: Diaphragm and ribs help in breathing activity.

During inhalation, ribs move up and outwards and the diaphragm moves down. This movement increases space in our chest cavity and air rushes into the lungs. The lungs get filled with air.

During exhalation, ribs move down and inwards, while diaphragm moves up to its former position. This reduces the size of the chest cavity and the air is pushed out of the lungs

Q20: Why is smoking bad for us?

Answer: Smoking contains harmful gases and substances which damages our lungs. These harmful substances can also cause lung cancer. We must avoid it.

Q21: How do birds breathe?

Answer: Birds have lungs for breathing.

Q22: How do insects breathe?

Answer: Insects have several small openings called spiracles on the lateral sides of their bodies. These spiracles lead to air tubes called trachea. Exchange of gases takes place through spiracles into the trachea.

Q23: Which cell organelle is a site for cellular respiration?

Answer: Mitochondria

Following youtube video shows breathing in various animals

Q24: Why do frogs have thin and moist skin?

Answer: Thin and moist skin helps frog in breathing.  Because of thin skin, gases can diffuse (or exchange through) easily. The moist surface also helps gases to dissolve and diffuse into and out of skin cells.


  1. Replies
    1. tnx for the all the question and answer,viedos r useful 2 us. you may give (mcq)

    2. there is different site for mcqs pagal

  2. this site is very useful for studing & exams

  3. thnx for the ques ..
    ek dammmm mast h...................
    par pata nahi n paper me kitne no. aayenge

  4. This comment has been removed by the author.

  5. Thanks for sample paper
    it was reeallyy helpfull............

  6. This comment has been removed by the author.

  7. this turned out to be really helpful...I have my exam tmrw and I'm sure that I am now 100% prepared for it!!!!!
    Thanks again!!!


  9. Thank you so much it's very helpful for my students


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