NCERT Solutions for Class 7 Science Chapter 10 Respiration in Organisms

These NCERT Solutions for Class 7 Science Chapter 10 Respiration in Organisms Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Respiration in Organisms NCERT Solutions for Class 7 Science Chapter 10

Class 7 Science Chapter 10 Respiration in Organisms Textbook Exercise Questions and Answers

Question 1.
Why does an athlete breathe faster and deeper than usual after finishing the race?
Answer:
During the run, the demand of energy is high but the supply of oxygen to produce energy is limited. Therefore, anaerobic respiration takes places in the muscle cells to fulfil the demand of energy. After finishing the race, an athlete breathes faster and deeper than usual so that more oxygen is supplied to the cells to resume aerobic respiration.

Question 2.
List the similarities and differences between aerobic and anaerobic respiration.
Answer:
Similarities:

In both the aerobic and the anaerobic respiration, food is broken down to release energy.
Both takes place inside the cells.
Both produce by products.

Differences:

Aerobic respiration	Anaerobic respiration
1. It uses oxygen in the process.	1. It takes place in the absence of oxygen.
2. In this process, glucose is completely broken down into CO₂, water along with release of energy.	2. In this process, glucose is broken into alcohol, CO₂and energy.
3. It occurs in all organisms like mammals.	3. It usually occurs in lower organisms like yeast (fungi) and bacteria. It can occur in the muscles of higher organisms during heavy activities.
4. It releases large amount of energy.	4. It releases less energy.

Question 3.
Why do we often sneeze when we inhale a lot of dust-laden air?
Answer:
We often sneeze when we inhale a lot of dust-laden air to expel out these foreign particles. These particles get past the hair in the nasal cavity and irritate the lining of the cavity which results in sneezing reflex.

Question 4.
Take three test-tubes. Fill each of them 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?
Answer:
Test-tube A will have the highest concentration of CO₂ because snail will take in oxygen dissolved in water and gives out CO₂. In test tube B, plant will release oxygen while in test tube C, the level of oxygen and carbon dioxide will remain stable due to gaseous cycle between the plant and the animal. The oxygen released by plant will be taken up by the animal while the carbon dioxide released by the animal will be taken up by the plant. Also, in test-tubes B and C, the CO₂ will be utilised by the water plant for synthesising food and hence there will be less concentration of CO₂ in these tubes.

Question 5.
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) move downwards

Question 6.
Match the items in Column I with those in Column II:

Column I	Column II
1. Yeast	(a) Earthworm
2. Diaphragm	(b) Gills
3. Skin	(c) Alcohol
4. Leaves	(d) Chest cavity
5. Fish	(e) Stomata
6. Frog	(f) Lungs and skin
7. Insects	(g) Tracheae

Answer:
1. (c)
2. (d)
3. (a)
4. (e)
5. (b)
6. (f)
7. (g)

Question 7.
Mark T if the statement is true and F if it is false:
a. During heavy exercise the breathing rate of a person slows down. (TV F)
b. Plants carry out photosynthesis only during the day and respiration only at night. (T/ F)
c. Frogs breathe through their skins as well as their lungs. (T/ F)
d. The fishes have lungs for respiration. (T/ F)
e. The size of the chest cavity increases during inhalation. (T/ F)
Answer:
a. F,
b. F,
c. T,
d. F,
e. T

Question 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.

a. The air tubes of insects
b. Skeletal structures surrounding chest cavity
c. Muscular floor of chest cavity
d. Tiny pores on the surface of leaf
e. Siriaii openings on the sides of the body of an insect
f. The respiratory organs of human beings
g. The openings through which we inhale
h. An anaerobic organism
i. An organism with tracheal system
Answer:

a. Trachea
b. Ribs
c. Diaphragm
d. Stomata
e. Spiracles
f. Lungs
g. Nostrils
h. Yeast
i. Ant

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

Extended Learning Activities and Projects

Question 1.
Observe fish in an aquarium. You will find flap like structures on both sides of their heads. These are flaps which cover the gills. These flaps open and close alternately. On the basis of these observations, explain the process of respiration in the fish.
Hint:
Respiration in fish takes place with the help of gills. Most fish possess gills on either sides of their head. Gills are the tissues made up of feathery structures that provide a large surface area for gaseous exchange. A large surface area is crucial for gaseous exchange in aquatic organisms as water contains very little amount of dissolved oxygen. Fish take in oxygen-rich water through their mouths and pump it over their gills. As water passes over the gill filaments, blood inside the capillary network picks up the dissolved oxygen. The circulatory system then transports the oxygen to all body tissues and ultimately to the cell, while picking up carbon dioxide, which is also removed from the body through the gills. After the water flows through the gills, it exits the body of the fish through the openings in the sides of the throat or through the operculum, a flap, usually found in bony fish, that covers and protects the fish gills.

Question 2.
Visit a local doctor. Learn about the harmful effects of smoking. You can also collect material on this topic from other sources. You can seek help of your teacher or parents. Find out the percentage of people of your area who smoke. If you have a smoker in your family, confront him with the material that you have collected.
Hint:
As this is an activity, the students are expected to do them on their own. Some harmful effects of smoking on our body are:
a. Smoking paves the way to hard drugs. Tobacco has been used by human beings for more than 400 years. It is smoked, chewed or used as a snuff.
b. Smoking is associated with increased incidents of cancer of lungs, urinary bladder and throat, bronchitis, emphysema, coronary heart disease, gastric ulcer, etc.
c. Tobacco chewing is associated with increased risk of cancer of the oral cavity.
d. Also, depression has been found to have a strong association with cigarette smoking. Adults who are depressed are 40% -50% more likely to smoke than adults who are not depressed.

Question 3.
Visit a doctor. Find out about artificial respiration. Ask the doctor:
a. When does a person need artificial respiration?
b. Does the person need to be kept on artificial respiration temporarily or permanently?
c. From where can the person get supply of oxygen for artificial respiration?
Hint:
a. Artificial respiration is needed by an individual at the time of acute breathing problems. It is an artificial method of breathing required when the person is unable to breathe normally.
b. Artificial respiration is not provided permanently to every person. It is given temporarily to person suffering from breathing problems. But artificial respiration can also be provided permanently to those who are in coma or unable to breathe on his or her own.
c. During artificial respiration, a cylinder filled with oxygen is attached to a machine which provides oxygen for artificial respiration.

Question 4.
Measure the breathing rate of the members of your family and some of your friends. Investigate:
a. if the breathing rate of children is different from that of adults.
b. if the breathing rate of males is different from that of females.
If there is a difference in any of these cases, try to find the reason.
Hint:
a. Children have faster respiratory rates than adults and the ‘normal’ respiratory rate can vary significantly by age.
b. Male heart rates are slower on average. Given these facts, it seems counterintuitive, but women have lower metabolic rates than men.

Activity 1

Objective: To show the variation in breathing rate during different activities.
Procedure: Perform the various activities as shown in the figure during a normal day and keenly observe your breathing rate.

Observation: When we do different activities, the rate of breathing increase or decrease depending on the activity. During sleeping and sitting, the breathing rate is slow while when we are doing physical activities like running, jumping, etc., the rate of breathing is fast.
Conclusion: Breathing rate depends upon the activity we do. Breathing rate of a person is not constant and it keeps changing.

Mechanism of Breathing in Humans:
In human beings, breathing occurs in the following way:

i. We take in the air present in the environment through our nostrils which travels through the nasal cavity. The mucous present here moistens and warms the air. The hair in the nasal cavity traps the dust and germs, thereby filtering the air.

ii. Then the air moves through the windpipe or trachea and reaches the lungs. The trachea divides into right and left primary bronchi that enters their respective lungs. Bronchi further divide and subdivide into bronchioles inside the lungs.

iii. The lungs are located in the chest cavity which is surrounded by the ribs.

iv. On the floor of the chest cavity lays a muscle sheet called diaphragm.

v. During the breathing process, the movement of the ribs and diaphragm takes place. This is so because the lungs expand and contract during breathing.

vi. As we take in the air, it fills up the lungs. This moves the diaphragm downwards and the ribs outwards and upwards. This increase space of chest cavity so that maximum air can be inhaled.

vii. When the lungs release out air from the body, it brings back the diaphragm and the ribs to their original positions, i.e., the ribs move downwards and inwards and the diaphragm moves upwards. This reduces the space in our chest cavity and pushes the air out.

Activity 2

Objective: To measure the change in size of the chest cavity during breathing.
Materials Required: Measuring tape.
Procedure:

Take a deep breath.
Measure the size of your chest with a measuring tape and record your observations.
Do the same process with your classmates and record your observations.
Now exhale complete air and measure the size again.

Observations:

S. No	Name of classmate	Chest measurement after expansion (Inhalation)	Chest measurement on relaxation (Exhalation)
1.	A
2.	B
3.	C

Conclusion: The chest expands during inhalation and contracts during exhalation.

Activity 3

Objective: To demonstrate how diaphragm in the body helps in the process of breathing in and out of the air.
Materials Required: Two glass bell jars, two Y-shaped glass tubes, two balloons, two rubber corks, two thin rubber sheets and a piece of string.
Procedure:

Take a wide plastic bottle and remove is bottom.
Get a Y-shaped glass or plastic tube.
Make a hole in the lid of the bottle so that the tube may pass through it.
To the forked end of the tube, fix two deflated balloons.
Introduce the tube into the bottle.
Now cap the bottle. Seal it to make it airtight.
To the open base of the bottle, tie a thin rubber or plastic sheet using a large rubber band.
To understand the expansion of the lungs, pull the rubber sheet from the base downwards.
The volume of the cavity increases. This causes the pressure to decrease.
Air rushes in to equalise the pressure, causing the balloons to inflate.
Next, push the rubber/plastic sheet up. The volume of the cavity decreases. This causes an increase in pressure within the bottle and the air rushes out of the balloons causing them to deflate.

Observation: When space in the jar is increased, balloons get inflated while when space in the jar is decreased, balloons get deflated.
Conclusion: When the lungs are filled with air, the diaphragm moves downward and when we exhale, the diaphragm moves upward.

Gases involved in Breathing: We inhale 21% oxygen and 0.04% carbon dioxide. Apart from this, small amounts of other gases present in the atmosphere are also involved in breathing. The exhaled air primarily contains large amount of carbon dioxide gas. This can be tested by blowing air into lime water. Lime water turns milky indicating presence of carbon dioxide gas.

Why Do We Sneeze?
As we inhale the air present in the surroundings, sometimes various unwanted elements such as smoke and dust are also included in it. However, they get stuck in the hair in our nostrils but some of them can get through the nasal cavity. They thus cause irritation in the nasal cavity which makes us sneeze. This helps in getting rid of the unwanted particles out of the nasal cavity.

Smoking damages lungs and can also cause cancer. Hence, it must be avoided. We should do regular breathing exercises (pranayam) as they increase our inhaling capacity, thereby bringing more energy to the body.

Breathing in Other Animals: Many animals have lungs in the bodies just like human beings, for example, lions, elephants, goats, cows, snakes and birds. However some animals have a different mechanism.
i. Breathing in Cockroach: Many insects like cockroaches have small openings called spiracles present on the sides of the bodies. Also, they have a network of air tube-like structures called the tracheae that allow the exchange of gases in these insects. The air enters the body through the spiracles into the tracheae and diffuses in the cells of the body. Similarly, the air from the cells enters the tracheal tubes and moves out of the body through spiracles.

ii. Breathing in Earthworm: Earthworms have a soft, slimy and moist skin. Hence, the gases can easily pass in and out of the earthworm’s body through its skin. Similarly, frogs also have a slippery and moist skin that can help in breathing. However, frogs possess lungs too. These animals, called the amphibians, can breathe on land by lungs and through moist skin under water. For example: frogs and toads.

iii. Breathing in Aquatic Animals:
Animals that live under water have special respiratory organs called gills. They are a comb-like structures present on the skin of these animals. Gills are richly supplied with blood vessels and allow the exchange of gases between animals and the water easily.

Respiration in Plants: Plants too require the phenomenon of respiration for survival. They also take in oxygen from the air and give out carbon dioxide. During this process, most of the plants use atmospheric oxygen to breakdown glucose into carbon dioxide and water with the release of energy.

In plants, breathing takes place through tiny holes or openings called stomata. Stomata trap the air and the exchange of carbon dioxide and oxygen takes places by the process called diffusion.

Root hair, lenticels and stomata are some of the parts present in plants for gaseous exchange. The roots of plants too respire to generate energy but they follow a different method. They take up air rich in oxygen from air spaces between the soil particles. Lenticels are the pores or cracks in the woody stems of plants that help in gaseous exchange.

Class 7 Science Chapter 10 Respiration in Organisms Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is respiration?
Answer:
Respiration is a biological process in which food is utilised to produce energy.

Question 2.
What is the end product of respiration in most of the organisms?
Answer:
Carbon dioxide, water and energy.

Question 3.
What is the end product of anaerobic respiration in muscle cells of humans?
Answer:
Lactic acid.

Question 4.
What is breathing?
Answer:
Breathing means taking in air rich in oxygen and giving out air rich in carbon dioxide with the help of respiratory organs.

Question 5.
What is inhalation?
Answer:
The taking in of air rich in oxygen into the body is called inhalation.

Question 6.
What is exhalation?
Answer:
Giving air rich in carbon dioxide out of the body is called exhalation.

Question 7.
What is the primary respiratory organ in humans?
Answer:
Lungs.

Question 8.
Which membrane controls the movement of lungs?
Answer:
Diaphragm.

Question 9.
What is the respiratory organ in fish?
Answer:
Gills.

Question 10.
What is the respiratory organ in a cockroach?
Answer:
Spiracles and tracheae.

Question 11.
How do birds breathe?
Answer:
Birds have lungs for breathing.

Question 12.
Why should we eat regularly?
Answer:
The food has stored energy which is released during respiration, thus we should eat regularly.

Question 13.
What forms the floor of the chest cavity?
Answer:
A large muscular sheet called diaphragm forms the floor of the chest cavity.

Question 14.
Why smoking should be avoided?
Answer:
Smoking damages lungs. Smoking is also linked to cancer. So, it must be avoided.

Question 15.
Give the general equation for aerobic respiration?
Answer:

Question 16.
Do we exhale only carbon dioxide or a mixture of gases along with it?
Answer:
No, some amount of moisture (water vapour) is also exhaled.

Question 17.
Which gas is released during exhalation?
Answer:
Mainly, carbon dioxide gas is released during exhalation.

Question 18.
Name an organism that can survive in the absence of air.
Answer:
Yeast can survive in the absence of air.

Question 19.
What does a breath mean?
Answer:
A breath means one inhalation plus one exhalation.

Question 20.
What are anaerobes?
Answer:
Some organisms, such as yeast, that can survive in the absence of air or oxygen are called anaerobes.

Short Answer Type Questions

Question 1.
What is aerobic respiration?
Answer:
The process of respiration which takes place in presence of oxygen is called aerobic respiration. In this process, breakdown of glucose (food) takes place into carbon dioxide and water with the help of oxygen.
Glucose (presence of oxygen) → Carbon dioxide + Water + Energy

Question 2.
What is anaerobic respiration?
Answer:
The process of respiration which takes place in the absence of oxygen is called anaerobic respiration. In this process, food is broken down without using oxygen into alcohol or lactic acid, carbon dioxide and energy.
Glucose (absence of oxygen) → Alcohol + Carbon dioxide + Energy

Question 3.
Do the plants also respire?
Answer:
Like other living organisms, plants also respire for their survival. They also take in oxygen from the air and give out carbon dioxide. In the cells, oxygen is used to break down glucose into carbon dioxide and water as in other organisms.

Question 4.
Why do we feel hungry after a physical activity?
Answer:
When we need extra energy, we breathe faster. As a result more oxygen is supplied to our cells. It speeds up the breakdown of food and more energy is released. Due to rapid breakdown of food, we feel hungry.

Question 5.
Give any two characteristics of all respiratory organs.
Answer:
Some characteristics of respiratory organs are:

Large surface area to get more oxygen.
Thin walls for easy diffusion and exchange of respiratory gases.
Rich blood supply for the transport of gases (except tracheal system).

Question 6.
How does exchange of gases take place in insects?
Or
Explain respiration in cockroach.
Answer:
The respiratory organs of insects include air tubes or trachea. They have small openings on the sides of their body which are called spiracles. Insects have a network of air tubes called tracheae for gaseous exchange. Oxygen-rich air enters through spiracles into the tracheal tubes and from here the air diffuses into the body tissues and reaches every cell of the body through finer branching of tracheal tubes called tracheoles. Thus, every cell gets oxygen directly. Similarly, carbon dioxide released by the cells, moves out through the spiracles.

Question 7.
What are the stages of respiration?
Answer:
Respiration takes place in the following stages:
a. External respiration or gaseous exchange: The exchange of gases between the environment and the body is called external respiration or gaseous exchange. This is also called breathing.

b. Internal respiration: It is a bio-chemical processes involved in respiration which breaks down the food using inhaled oxygen to release energy and takes place in the tissues within the cells of an organism. Thus, this is also called the cellular or tissue respiration.

Question 8.
What are gills? Where can they be seen?
Answer:
Gills in fish help them to use oxygen dissolved in water. Gills are the projections of the skin and are well supplied with blood vessels for exchange of gases. These gills can be seen in most of the aquatic animals like fish, prawns and mussels where they function as their respiratory organs.

Question 9.
Explain anaerobic respiration in yeast cells and in our muscles.
Answer:
Anaerobic respiration in yeast cells: Yeast gets energy through anaerobic respiration. In the absence of oxygen, yeast respires and breaks down glucose into alcohol and carbon dioxide. Following reaction takes place without the use of oxygen:
Glucose (without oxygen) → Alcohol + Carbon dioxide + Energy

Anaerobic respiration in Muscles: Our muscles can also respire anaerobically, but only for a short time. During heavy exercise, anaerobic respiration takes place in which glucose is broken into lactic acid and energy. Following reaction takes place in absence of oxygen:
Glucose (in muscles) → Lactic acid + Energy

Question 10.
What is the function of large intercellular spaces in plants?
Answer:
The large inter-cellular spaces ensure that all cells are in contact with air. Both CO₂ and O₂ are exchanged by diffusion in the intercellular spaces. These gases can either go into the cells or away from them or out into the air.

Question 11.
Explain respiration in earthworm.
Answer:
Earthworm breathes through its moist skin. The skin of an earthworm feels moist and slimy on touching and gases can pass easily through them.

Question 12.
What is the importance of breathing?
Answer:
All the organisms need energy for their various functions. This energy is released from the breakdown of the food (glucose) with the help of oxygen. The breathing ensures the continuous supply of oxygen to different body cells for this process.

Long Answer Type Questions

Question 1.
Describe the respiratory system in humans.
Answer:
When we breathe in, the air enters through our nostrils. Hair and the moist inner lining of the nose prevent the dust and germs from entering the respiratory system. The air passing the nasal passage gets warm and moist and enters the lungs through trachea and bronchi. In lungs, each bronchus divides into smaller tubes called bronchioles.

At the other end of these bronchioles, there are very small air sacs called alveoli. These air sacs are surrounded by blood vessels. These blood vessels absorb oxygen present in the air we breathe in. Carbon dioxide present in the blood is released into the air sacs and is expelled out of our body when we breathe out. Thus during breathing, exchange of oxygen and carbon dioxide takes place in the lungs.

Question 2.
What is meant by breathing rate? Explain the mechanism of inhalation and exhalation which are responsible for breathing rate?
Answer:
The number of times a person breathes in a minute is termed as the breathing rate. During breathing, inhalation and exhalation take place alternately. A breathe means one inhalation plus one exhalation. During inhalation, ribs move up and outwards and diaphragm moves down. This movement increases space in our chest cavity and air mshes into the lungs. The lungs get filled with air. During exhalation, ribs move down and inwards, while diaphragm moves up to its original position. This reduces the size of the chest cavity and air is pushed out of the lungs.

Question 3.
Explain the mechanism of respiration in plants?
Answer:
Plants can be of various sizes. Developing respiratory organs could not be a fruitful solution for plants because of their unlimited growth. Each plant part breathes through its external layer of cells. Roots breathe through root hair by taking air from spaces between soil particles. Stems breathe through lenticels and epidermis. Leaves have numerous small pores or openings called stomata. Stomata trap air and the exchange of carbon dioxide and oxygen takes places by a process called diffusion.

Question 4.
Differentiate between cellular respiration and breathing.
Answer:

Cellular respiration	Breathing
1. The process of chemical breakdown of food in the cell with the release of the energy is called cellular respiration.	1. The taking in of air rich in oxygen and giving out air rich in CO₂ with the help of respiratory organs is called breathing.
2. It releases energy.	2. It requires energy.
3. It occurs in all individual cells.	3. It occurs only in the specialised organs called lungs.
4. It is a chemical process.	4. It is a physical process.

Question 5.
Write some differences between respiration and combustion.
Answer:

Respiration	Combustion
1. Respiration is the process of oxidation of food materials like glucose, amino acids, fatty acids to water and carbon dioxide.	1. Combustion is the process of burning sugar to form water and carbon dioxide which helps in the release of energy in the form of heat.
2. Respiration does not require any external heat to carry on the process.	2. Combustion is only done by applying external heat to the sugar molecule to bum.
3. In respiration, there is no charring of sugar during oxidation.	3. In combustion, the sugar is melted, chars are later burned to produce flame.
4. In respiration, energy is released in several stages throughout the process.	4. In combustion, energy is released only once.
5. The energy released from respiration is in the form of ATP and heat.	5. The energy released from combustion is in the form of heat.
6. Several intermediary products are formed during the process of respiration.	6. No intermediary products are formed during the process of combustion.
7. Respiration is of two types: aerobic respiration and anaerobic respiration.	7. The combustion is also called as process of rapid oxidation.

Picture-Based Questions

Question 1.
Draw a diagram of open and closed stomata.
Answer:

Question 2.
Draw a diagram of a fish and label the position of gills in it.
Answer:

Question 3.
a. Observe the given picture. What does it show?
b. Label the parts of the body marked as A, B and C.
c. Identify the structure D and state its function.

Answer:
a. The given picture shows the human respiratory system.
b. A-Nostril; B-Trachea; C-Lung
c. D is the diaphragm. It moves up and down to increase and decrease the space of chest cavity during inhalation and exhalation, respectively.