Lesson: Respiration in Organisms

Multiple Choice Questions

Question: 1

Sometimes when we do heavy exercise, anaerobic respiration takes place in our muscle cells. What is produced during this process?

a)      Alcohol and lactic acid

b)      Alcohol and CO2a

c)      Lactic acid and CO2

d)      Lactic acid only



Question: 2

Yeast is used in wine and beer industries because it respires:

(a)   Aerobically producing oxygen.

(b)   Aerobically producing alcohol.

(c)   An aerobically producing alcohol.

(d)   An aerobically producing CO2.



Question: 3

During the process of exhalation, the ribs move:

(a)   down and inwards.

(b)   up and inwards.

(c)   down and outwards.

(d)   up and outward.



Question: 4

Breathing is a process that:

(i)                 provides O2 to the body

(ii)              breaks down food to release energy

(iii)            helps the body to get rid of CO2

(iv)             produces water in the cells

Which of the following gives the correct combination of functions of breathing?

a)      (i) and (ii)

b)      (ii) and (iii)

c)      (i) and (iii)

d)      (ii) and (iv)



Question: 5

Fish breathe with the help of gills which are richly supplied with blood vessels. The gills help the fish to:

(a)   Take in oxygen from air.

(b)   Take in oxygen dissolved in water.

(c)   Absorb nutrients present in water.

(d)   Release waste substances in water.



Question: 6

Earthworms and frogs breathe through their skin because of which the skin of both the organisms is:

(a)   Moist and rough.

(b)   Dry and rough.

(c)   Dry and slimy.

(d)   Moist and slimy.



Very Short Answer Questions

Question: 7

Mark the following statements as True or False. Correct the false statements.

(a)   Oxygen breaks down glucose outside the cells of organisms.

(b)   Frogs can breathe through their skin as well as lungs.

(c)   Insects have spiracles on the lower surface of the body.

(d)   Exhaled air has more percentage of CO2 than inhaled air.


(a)   False. Oxygen breaks down glucose inside the cells of organisms.

(b)   True

(c)   False. Insects have spiracles on the sides of the body.

(d)   True

Question: 8

Fill in the blanks with suitable words.

(a)   The roots of a plant take up oxygen from the ______ trapped between the ________ particles.

(b)   Diaphragm forms the ___________ of the chest cavity.

(c)   Exchange of gases in the leaves take place with the help of __________.

(d)   Cockroaches breathe with the help of air tubes called ___________.


(a)               air, soil

(b)               floor

(c)               stomata

(d)               tracheae

Short Answer Questions

Question: 9

Pick the odd-one-out from each of the groups given below on the basis of respiratory organs. Give reason for your answer.

(a)   Cockroach, grasshopper, snail, ant

(b)   Lizard, cow, earthworm, snake

(c)   Crocodile, whale, dolphin, fish

(d)   Snake, tadpole, crow, goat


(a)               Snail. It does not use trachea for breathing.

(b)               Earthworm. It breathes through its skin, and lacks lungs.

(c)               Fish. It breathes through gills, and lacks lungs.

(d)               Tadpole. It breathes through gills and lacks lungs.

Question: 10

Which gas present in air is essential for aerobic respiration? What is the role of oxygen during respiration?


Oxygen present in air is essential for aerobic respiration. The role of oxygen during respiration is breaking down the food and releasing energy.

Question: 11

On an average, an adult human being at rest breathes 15 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY=Hhbbf9v8qqaqFr0x c9pk0xbba9q8WqFfea0=yr0RYxir=Jbba9q8aq0=yq=He9q8qqQ8fr Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaaieaaju gGbabaaaaaaaaapeGaa83eGaaa@3978@ 18 times per minute. The breathing rate, however, may differ under different conditions. Arrange the following activities given in the box in order of increasing breathing rates and give reason for your answer:

sleeping, cycling, brisk walk, watching T.V


The activities in increasing order of breathing rates are given below:

Sleeping, watching T.V., brisk walk, and cycling.

Whenever a person is sleeping, he is at complete rest with slow breathing rate; watching TV shows slightly more activity so the breathing rate will be more than sleeping. With activities like a brisk walk, the breathing rate becomes higher, and with cycling where there is strenuous work by the body muscles, more oxygen is required to provide energy to the cells, hence breathing rate also increases to draw in more oxygen from the air.

Question: 12

On a very cold morning, Boojho and Paheli were talking with each other as they walked down to their school. They observed that the air coming out of their mouth looked like smoke. They were amused and wondered how it happened. Help them find the answer.


On a cold day while exhaling, the moist and warm air coming out from our nose and mouth condenses into mist, as it comes in contact with the cold air outside. This mist appears as a white smoke.

Question: 13

Whenever we feel drowsy or sleepy, we start yawning. Does yawning help us in anyway?


When we are sleepy or drowsy, our breathing rate goes down. The lungs do not receive enough oxygen from the air causes yawning.

Thus, yawning helps to bring more oxygen from the air into the lungs, which in turn help us to remain awake.

Question: 14

Insects and leaves of a plant have pores through which they exchange gases with the atmosphere. Can you write two points of differences between these pores with respect to their position, number and extension into the body?


(i)     Stomata are observed on the lower surface of leaves, while spiracles are found on the sides of an insect’s body.

(ii)  Spiracles are less in number when compared to stomata.

(iii)            Stomata are just openings on lower leaf surfaces, while Spiracles are associated with extensive network of the tracheal system.

Long Answer Questions

Question: 15

Paheli participated in a 400 m race competition held at her school and won the race. When she came home, she had mixed feelings of joy and pain as she had cramps in her leg muscles.

After a massage she was relieved of the pain. Answer the following questions related to the situation.

(a)   What can be the possible reasons for the pain in her legs?

(b)   Why did she feel comfortable after a massage?


(a)   The leg pain was because of the cramps that take place when there is an accumulation of lactic acid in the muscles. Our muscle cells produce lactic acid by anaerobic respiration while running or doing heavy exercise.

(b)   She felt relief after a massage because it improved the blood flow, which resulted in an increased supply of oxygen to the muscle cells. The increased oxygen helped in breaking down the lactic acid to produce water and carbon dioxide.

Question: 16

Observe the figure given below carefully and answer the following questions.

(a)            In which jar, will the amount of CO2 be the highest and why?

(b)            In which jar, will the amount of CO2 be the lowest and why?


(a)               In jar C, the amount of CO2 will be the highest. This is because the mice kept in it will continuously exhale CO2, thereby increasing its amount.

(b)               In jar A, the amount of CO2 will be the lowest, as the amount of this gas released during respiration will in turn be used up in photosynthesis by the plants.

Question: 17

Observe the figure given below carefully and answer the following questions.

(a)             Which process is being tested in the activity?

(b)            What is the result of the activity? Give reasons.


(a)               The process of exhalation which is a part of respiration.

(b)               The lime water in test tube ‘B’ will turn milky, as CO2 from the exhaled air will react with the lime water to produce a milky solution. However, water in test tube ‘A’ will remain unchanged as it doesn’t undergo any chemical reactions with the CO2.

Question: 18

A food stall owner was preparing dough for making bhaturas. He added a pinch of yeast and sugar to the dough and left it in a warm place. After few hours, the dough had risen. There was a sour smell too.

(a)   Why did the dough rise?

(b)   Why did the dough smell sour?

(c)   Why was sugar added to the dough?

(d)   What would have happened if the dough was kept in the refrigerator, soon after it was prepared?


(a)               The dough rises owing to the presence of CO2 which is released by the yeast during respiration.

(b)               During anaerobic respiration by the yeast, alcohol is the end product which causes the sour smell.

(c)               Sugar forms the base or food for the yeast.

(d)               The dough will not rise or produce a sour smell if kept in the fridge, as yeasts do not respire or multiply in low temperatures.

Question: 19

Observe the figures (A) and (B) and answer the following.

Which of the figures A or B indicates the process of inhalation and which the process of exhalation?

In the figure, label the arrows and indicate the direction of

(a)   Movement of air

(b)   Movement of diaphragm

(c)   Movement of ribs


Fig. (A) Inhalation

Fig. (B) Exhalation

Question: 20

Match the names of organisms in Column I with their organs of breathing given in Column II.


(a)               iii

(b)               iv

(c)               i

(d)               ii