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Respiration In Organisms

Class 7th Science NCERT Exemplar Solution
Multiple Choice Questions
  1. Sometimes when we do heavy exercise, anaerobic respiration takes place in our muscle…
  2. Yeast is used in wine and beer industries because it respiresA. aerobically producing…
  3. During the process of exhalation, the ribs moveA. down and inwards. B. up and inwards. C.…
  4. Breathing is a process that (i) provides O2 to the body. (ii) breaks down food to release…
  5. Fish breathe with the help of gills which are richly supplied with blood vessels. The…
  6. Earthworms and frogs breathe through their skin because of which the skin of both the…
Very Short Answer Questions
  1. Mark the following statements as True or False. Correct the false statements. (a) Oxygen…
  2. Fill in the blanks with suitable words. (a) The roots of a plant take up oxygen from the…
Short Answer Questions
  1. Pick the odd-one-out from each of the groups given below on the basis of respiratory…
  2. Which gas present in air is essential for aerobic respiration? What is the role of oxygen…
  3. On an average, an adult human being at rest breathes 15-18 times per minute. The breathing…
  4. On a very cold morning, Boojho and Paheli were talking with each other as they walked down…
  5. Whenever we feel drowsy or sleepy, we start yawning. Does yawning help us in anyway?…
  6. Insects and leaves of a plant have pores through which they exchange gases with the…
Long Answer Questions
  1. Paheli participated in a 400 m race competition held at her school and won the race. When…
  2. Observe Figure 10.1 carefully and answer the following questions. (a) In which jar, will…
  3. Observe Figure 10.2 carefully and answer the following questions. (a) Which process is…
  4. A food stall owner was preparing dough for making bhaturas. He added a pinch of yeast and…
  5. Observe the figures given as Figure 10.3 (A) and (B) and answer the following. (a) Which…
  6. Match the names of organisms in Column I with their organs of breathing given in Column…

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 CO2

C. lactic acid and CO2

D. lactic acid only


Answer:

During some heavy exercises like running, cycling, weightlifting etc. tge demand for energy is quite high which creates a temporary deficiency of oxygen in the muscle cells. It causes muscle cells to respire anaerobically for a limited span of time. The glucose present in the muscle cells is converted into lactic acid and also release energy for further work.


Question 2.

Yeast is used in wine and beer industries because it respires
A. aerobically producing oxygen.

B. aerobically producing alcohol.

C. anaerobically producing alcohol.

D. anaerobically producing CO2.


Answer:

Yeasts are single celled organisms which respire anaerobically. These are used in making of beer and wine and are added as precursors. While anaerobically respiring they produce alcohol which is useful product in the production of wine and beer.


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.


Answer:

The process of removal of the air from the lungs which is rich in carbon dioxide is known as exhalation. During this process the main aim is to empty the lungs, therefore, ribs move down and inwards, diaphragm moves up. This reduces the size of the chest cavity and air is released out of the body.


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)


Answer:

Breathing is the process of intake of air which is rich in oxygen thus supplying oxygen to the whole body (inhalation) and then removal of the air which is rich in carbon dioxide(exhalation). Combined these processes are known as breathing.


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.


Answer:

Different organisms have different respiratory organs. In humans it is the lungs while in the aquatic animals like fishes it is the gills. Gills are actually the projections of the skin which are richly supplied in blood vessels. They help in taking the oxygen which is dissolved in water. Afterwards the process of respiration takes place.


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.


Answer:

We humans respire through lungs, fishes through gills, the same way earthworm and frog respire through their skin. The skin of such animals is thin, moist and slimy which help in easy gaseous exchange show the skin, thus, facilitating respiration.

Fogs can also respire through lungs.



Very Short Answer Questions
Question 1.

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.


Answer:

a) FALSE. The breakdown of glucose into carbon dioxide and energy is done using oxygen inside the cell. This process is known as respiration.

b) TRUE. Likewise humans frogs also can respire through lungs. In addition to lungs frogs can also respire through their skin which is thin, moist and slimy and help in easy gaseous exchange.


c) FALSE. Spiracles are the tiny pores present in the insects like cockroaches which help in gaseous exchange. These small spiracles are present on the lateral body (sides) of the organism.


d) TRUE. The percentage of CO2 in inhaled air is 0.04% whereas in exhaled air it is 4.4%. Therefore, we can say that exhaled air has more percentage of carbon dioxide than in the inhaled air.



Question 2.

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 ___________.


Answer:

a) The roots of a plant take up oxygen from the air trapped between the soil particles.

The roots use up the oxygen available to them from the air spaces present between the soil particles.


b) Diaphragm forms the floor of the chest cavity.


The movement of diaphragm along with the ribs helps in breathing.


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


The stomata are the tiny pores (openings) present on the surface of leaves which help in transportation of Oxygen and Carbon dioxide in and out of the leaves.


d) Cockroaches breathe with the help of air tubes called trachea. Insects have a network of air tubes known as trachea which facilitates respiration.




Short Answer Questions
Question 1.

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


Answer:

a) SNAIL.

The other animals mentioned above like cockroach, grasshopper and ant are insects and respire through trachea while snail being a molluscan has different organ of respiration.


b) EARTHWORM.


The rest of the animals like lizard, cow and snake respire through lungs whereas only earthworm respire through moist skin.


c) FISH.


All the other animals like crocodile, whale and dolphin have lungs as their respiratory organs but only fish respire through gills.


d) TADPOLE.


It is the odd one as tadpoles respire through gills and do not have lungs while all other mentioned animals have lungs.



Question 2.

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


Answer:

Aerobic respiration is the type of respiration which occur in the presence of oxygen.

Oxygen is a very essential part of the aerobic respiration.

Oxygen is used for theoxidation of the food that we eat into smaller molecule which is further used in creation of energy to do work and maintain proper functioning of body organs


Question 3.

On an average, an adult human being at rest breathes 15–18 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.


Answer:

sleeping < watching TV < brisk walk < cycling

The number of times a person breathes in a minute is known as the breathing rate. Normally it is 15 to 18 times per minute but can change depending upon the type of work a person is doing. During heavy exercise the breathing rate can increase upto 25 times per minute. This can be noticed while running that we take not only fast breaths but deep breaths also.


During sleepingthe human body is completely at rest and therefore the oxygen required by the body is minimum.


While watching TVno extra work is done but atleast the body is awake and therefore the requirement of oxygen by the body is slightly more than while the person is sleeping.


While brisk walkthe amount of oxygen needed is more and hence the breathing rate would definitely be more.


While cycling, the breathing rate would be maximum. It can go up to 25 times per minute.



Question 4.

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.


Answer:

This is a very common observation. On any cold day we can observe the air exhaled by us turning into white smoke. This is because the air exhaled by us is moist and warm and as soon as it comes in contact with the cold atmospheric air it turns into white smoke.



Question 5.

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


Answer:

When we are sleepy or drowsy our breathing rate slows down causing deficiency of oxygen in our body. The lungs do not get enough oxygen and hence it is our body reflex to yawn, thus opening the mouth wide enough to get sufficient oxygen.



Question 6.

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.


Answer:

Spiracles are the tiny pores present in the insects like cockroaches which help in gaseous exchange whereas stomata are the openings present on the surface of the leaves. They also help in gaseous exchange. The differences between the two structures are as follows:

•Spiracles are present laterally i.e. on the sides of the body of the organism whereas the stomata are present on the surface of the leaves.


•Spiracles are less in number as compared to that of the stomata.




Long Answer Questions
Question 1.

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?


Answer:

a) During heavy exercise like running a deficiency of oxygen is created in the muscle cells. This deficiency leads to anaerobic respiration in the muscle cells. During anaerobic respiration glucose which is present in the muscle cells breaks down into lactic acid which gets accumulated in the muscle cells of the legs thus causing pain and cramps.

b) While massaging, the flow of blood in the blood vessels (circulation) increases thus increasing the oxygen supply to the muscle cells. The proper supply of oxygen leads to complete breakdown of glucose.



Question 2.

Observe Figure 10.1 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?


Answer:

In jar A only plant is present and plants take up the carbon dioxide present the atmospheric air. In jar B along with the plant, mice are also kept. The mice release carbon dioxide which is taken by the plants as required. In jar C only mice are present so large amount of carbon dioxide is produced.

a) In jar C the amount of CO2 would be maximum because only mice are present and no plants to use up CO2 generated.


b) The amount of CO2 would be minimum in the jar A and there is no animal present to release CO2 and the CO2 which is present in the air of the jar is also taken up by the plants.



Question 3.

Observe Figure 10.2 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.


Answer:

a) As the air is being released from the nose, the process of exhalation is being tested here.

b) In the first case i.e. test tube A only water is present in the test tube so even if CO2 is exhaled out no chemical reaction will happen but in the second case when lime water is present in the test tube and CO2 enters it, CO2 reacts with lime water (calcium hydroxide) and produce calcium carbonate which is milky in appearance.



Question 4.

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?


Answer:

a) Yeast are the single cell organisms which perform anaerobic respiration. The dough rose because of the release of carbon dioxide which is a product of anaerobic respiration.

b) The dough becomes sour because of the production of alcohol produced during the anaerobic respiration by Yeast.


c) A pinch of sugar is added to the dough for yeast to feed upon it and multiply.


d) If the dough is kept in refrigerator as soon as it is prepared there would be no change in it. Yeast requires warm climate to grow and multiply and as there is low temperature inside a refrigerator, there would notbe the perfect climate for yeast to grow.



Question 5.

Observe the figures given as Figure 10.3 (A) and (B) and answer the following.

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

(b) In the figure label the arrows and indicate the direction of

(i) movement of air

(ii) movement of diaphragm

(iii) movement of ribs



Answer:

a) Diagram A shows the process of inhalation as during inhalation only air enters the wind pipe (trachea), ribs move outwards and the diaphragm moves downwards thus creating space for air to move in. In the diagram B, the process of exhalation is seen as the air move outward from the wind pipe, ribs move inwards and the diaphragm upward thus helping to push air out.

b)



A- Rib cage moving outward (case of inhalation)


B- air coming inside the body (case of inhalation)


C- diaphragm moving downward (case of inhalation)


D- ribs moving inward (case of exhalation)


E- air coming out from the body (case of exhalation)


F- diaphragm moving upward (case of exhalation)



Question 6.

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



Answer:

(a) butterfly - (iii) spiracles

spiracles are the small pores present on the lateral surface of the body. They are the organs of respiration in insects.


(b) earthworm - (iv) skin


The earthworm respires through the moist and slimy skin which facilitates the transfer of oxygen and carbon dioxide.


(c) sparrow - (i) lungs


lungs are the most advanced but complex respiratory structures mostly found in well-developed birds, reptiles and mammals.


(d) fish - (ii) gills


gills are the covering of the skin which help the fishes take up dissolved oxygen in water.