Class 7 Science Chapter 10 Important Questions

Class 7 Science Chapter 10 Important Questions Answers and Main Keywords of Respiration in Organisms updated for academic session 2020-2021. Class 7 Chapter 10 Science Respiration in Organisms all important extra questions with suitable answers are helpful for all boards.

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Class 7 Science Chapter 10 Important Questions for 2020-2021

Class: 7Science
Chapter: 10Respiration in Organisms
Contents:Extra Questions with Answers

Class 7 Science Chapter 10 Important Questions Set – 1

Why do we respire?

We know that all organisms are made of small microscopic units called cells. A cell is the smallest structural and functional unit of an organism. Each cell of an organism performs certain functions such as nutrition, transport, excretion and reproduction. To perform these functions, the cell needs energy. The food has stored energy, which is released during respiration. Therefore, all living organisms respire to get energy from food.

What do you mean by “Cellular Respiration”?

During breathing, we breathe in air that air contains oxygen. We breathe out air which is rich in carbon dioxide. The air, we breathe in, is transported to all parts of the body and ultimately to each cell. In the cells, oxygen in the air helps in the breakdown of food. The process of breakdown of food in the cell with the release of energy is called cellular respiration. Cellular respiration takes place in the cells of all organisms.

What do you mean by respiration?

Respiration occurs in all the living cells (plant or animal). The process of respiration involves taking in oxygen of air into the cells, using it for releasing energy by burning food, and then eliminating the waste products (carbon dioxide and water) from the body. During respiration, the energy rich food (like glucose) is broken down by oxygen into carbon dioxide and water, and energy is released. This energy is further used by the organisms. The process of respiration can be written in the form of a word equation as follows:
Glucose + Oxygen + Respiration (in the body cells) → Carbon dioxide + Water + Energy

“Respiration process is known as the reverse of photosynthesis” – Comment.
The process of respiration is the reverse of photosynthesis, this is because photosynthesis is the making of food (like glucose) by absorbing light energy, whereas respiration is the breaking of food (like glucose) to release energy.

What do you know about “Aerobic Respiration”?

In the cell, the food (glucose) is broken down into carbon dioxide and water using oxygen. When breakdown of glucose occurs with the use of oxygen it is called aerobic respiration. Most of the living organisms carry out aerobic respiration by using oxygen of air. Aerobic respiration produces much more energy because complete breakdown of glucose occurs during aerobic respiration by the use of oxygen. All the organisms which obtain energy by aerobic respiration cannot live without the oxygen of air.

Class 7 Science Chapter 10 Important Questions Set – 2

What do you know about “Anerobic Respiration”?

When breakdown of glucose occurs without the use of oxygen it is called anaerobic respiration. Only a few living organisms carry out anaerobic respiration to obtain energy without using oxygen of air. Anaerobic respiration produces much less energy because partial breakdown of glucose occurs during anaerobic respiration in the absence of oxygen. The products of this partial breakdown of glucose are alcohol and carbon dioxide and energy. All the organisms which obtain energy by anaerobic respiration can live without the oxygen of air.

Discuss the anaerobic respiration of yeast.

Yeast is single-celled organism. Yeast is used to make alcohol drinks such as wine and beer and bread. In anaerobic respiration, the micro-organisms like yeast break down the glucose in the absence of oxygen to form alcohol and carbon dioxide and release energy. In bread-making, the carbon dioxide produced by yeast makes the bread rise. Ans also yeast converts glucose into alcohol in anaerobic respiration. Yeast produces much less energy because only partial breakdown of glucose occurs in an aerobic respiration in the absence of oxygen.

How does anaerobic respiration take place in our muscle and we get energy from it?

Our muscle cells can also respire anaerobically, but only for a short time, when there is a temporary deficiency of oxygen. During heavy exercise, fast running, cycling, walking for many hours or heavy weight lifting, the demand for energy is high. But the supply of oxygen to produce the energy is limited. Then anaerobic respiration takes places in the muscle cells to fulfil the demand of energy.

“After heavy physical exercise, we sometimes get muscle cramps” – Why?
The cramps occur when muscle cells respire anaerobically. After heavy physical exercise or very fast running etc., we get sometimes muscles cramps. It means painful contraction of muscles are called cramps. During heavy exercise, some of our muscles respire anaerobically the anaerobic respiration by muscles bring about partial breakdown of glucose to form lactic acid. This lactic acid accumulates in the muscles. The accumulation of lactic acid in the muscles causes muscle cramps.




How do we get relief from muscle cramps?

The cramps occur when muscle cells respire anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps. We get relief from cramps after a hot water bath or a massage. Hot water bath or massage improves circulation of blood. As a result, the supply of oxygen to the muscle cells increases. The increase in the supply of oxygen results in the complete breakdown of lactic acid into carbon dioxide and water.

Class 7 Science Chapter 10 Important Questions Set – 3

What do you mean by breathing?

Breathing means taking in air rich in oxygen and giving out air rich in carbon dioxide with the help of respiratory organs. The taking in of air rich in oxygen into the body is called inhalation and giving out of air rich in carbon dioxide is known as exhalation. It is a continuous process which goes on all the time and throughout the life of an organism.

What do you mean by breathing rate?

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 breath means one inhalation plus one exhalation.

Discuss the breathing rate in adults and child.

Average breathing rate in an adult human being at rest is 15 to 18 times per minute. The breathing rate of a person changes according to the oxygen requirement of the body. The breathing rate of a person increases with increased physical activity like running, weightlifting etc. During heavy exercise, the breathing rate can increase up to 25 times per minute. While we exercise, not only do we breathe fast, we also take deep breaths and thus inhale more oxygen. Another point is to be noted that the breathing rate in children is higher than that of adults, children breath about 20 to 30 times per minute.

List the similarities and differences between aerobic and anaerobic respiration.
Differences between aerobic and anaerobic respiration are as:

    • i) Aerobic respiration occurs in the presence of oxygen whereas anaerobic respiration occurs in the absence of oxygen.
    • ii) Aerobic respiration creates large amount of energy is released whereas anaerobic respiration creates small amount of energy is released.
    • iii) In aerobic respiration food molecules are broken down into water and carbon dioxide whereas in anaerobic respiration food molecules are broken down into ethyl alcohol and carbon dioxide.
    • Similarities: Both aerobic and anaerobic respiration produce energy and keep out carbon dioxide.



Explain the respiratory system in humans.

We take air through our nostrils. When we inhale air, it passes through our nostrils into the nasal cavity. From nasal cavity the air reaches our lungs through the windpipe. Lungs are present in the chest cavity. This cavity is surrounded by ribs on the sides. A large muscular sheet called diaphragm form the floor of the chest cavity. Breathing involves the movement of the diaphragm and the rib cage.

Class 7 Science Chapter 10 Important Questions Set – 4

Explain an anaerobic respiration in yeast and in our muscles.

In Yeast: Yeast gets energy through anaerobic respiration. In the absence of oxygen, glucose breaks down into alcohol and carbon dioxide.
In muscles: Our muscles can also respire anaerobically, but only for a short time. During heavy exercise, anaerobic respiration take place in which glucose is broken down into lactic acid and energy.

Discuss the breathing mechanism of human body.

The chest cavity is separated from the abdomen by a muscular wall called diaphragm. When diaphragm move downwards and ribs move up and outwards, the space in chest cavity increases. As a result, air from atmosphere rushes through nose, trachea to lungs (inhalation or inspiration). When the diaphragm moves upwards to its original position, ribs moves down and inward, the space in the chest cavity decreases. As a result, air from lung is forced out of the body through air passage (exhalation or expiration).

What is the percentage of oxygen and carbon dioxide in inhaled and exhaled air?

When we inhale oxygen, during the process of respiration glucose is broken down to release energy. In the case of inhalation, some of the oxygen is used up, whereas carbon dioxide and water are produced. This is why, the exhaled air contains less of oxygen but more of carbon dioxide and more of water vapor.
In an inhaled air, the amount of oxygen and carbon dioxide are 21%, 0.04% and a little water vapor is taken. And in exhaled air, the amount of oxygen and carbon dioxide are 16%, 4.4% and a lot of water vapor is released.

Discuss the respiratory system in cockroach.
A cockroach has small openings on the sides of its body. Other insects also have similar openings. These openings are called spiracles. Insects have a network of air tubes called tracheae for gas exchange. Oxygen rich air rushes through spiracles into the tracheal tubes, diffuses into the body tissue, and reaches every cell of the body. Similarly, carbon dioxide from the cells goes into the tracheal tubes and moves out through spiracles. These air tubes or tracheae are found only in insects and not in any other group of animals.




Write down the respiratory system in earthworm.

The earthworm breathes through its skin. The skin of earthworm is quite thin and moist. Gases can easily pass through the skin of earthworm. The skin of earthworm has a good blood supply. So, the earthworm absorbs the oxygen of air needed for respiration through its thin and moist skin. This oxygen is then transported to all the cells of the earthworm by its blood where it is used in respiration. The carbon dioxide produced during respiration is carried back by the blood.
This carbon dioxide is expelled from the body of the earthworm through its skin. Thus, in earthworm the exchange of gases take place through the thin and moist skin. Although frogs have a pair of lungs like human beings, they can also breathe through their skin, which is moist and slippery.

Class 7 Science Chapter 10 Important Questions Set – 5

Write down the natural defence mechanism of our nostril, when we inhale dust or foreign materials?

The air around us has various types of unwanted particles, such as smoke, dust, pollen, etc. When we inhale, the particles get trapped in the hair present in our nasal cavity. However, sometimes these particles may get past the hair in the nasal cavity. Then they irritate the lining of the cavity, as a result of which we sneeze. Sneezing expels these foreign particles from the inhaled air and a dust- free, clean air enters our body.
When you sneeze, you should cover your nose so that the foreign particles you expel are not inhaled by other persons.

Write short notes on “effect of smoking”.

The lungs are very delicate organs which are essential for breathing and keeping us alive. The biggest enemy of our lungs is the habit of smoking. Smoking send tobacco smoke inside the body. The chemicals present in tobacco smoke damage the lungs in many ways. Smoking cause heart diseases. Smoking causes lung cancer. Smoking destroys the lung tissue gradually due to which breathing becomes very difficult. Smoking also damages the health of non-smokers who inhale the air containing tobacco smoke. And smoking kills gradually. Many people die every year from disease caused by smoking. The bad habit of smoking must be avoided to lead a healthy life.

Explain the respiration in plants.

Plants take in oxygen and give out carbon dioxide in the cells, oxygen is used to break down glucose into carbon dioxide and water as in other organisms. In plants each part can independently take in oxygen from the air and give out carbon dioxide. Leaves of the plant have tiny pores called “stomata” for exchange of oxygen and carbon dioxide. Like all other living cells of plants, the root cells also need oxygen to generate energy. Roots take up air from the air spaces between present between the soil particles. The stems of some plants have tiny pores called “lenticels” which help in exchange of gases.

What are the differences between respiration and combustion?
In respiration, the energy released which is stored in chemical molecules whereas the energy released does not get stored in combustion. In respiration, no release of light and heat whereas heat and light is released in combustion. In respiration, step wise release of energy, no rise in sudden temperature whereas in combustion, fast reaction and sudden release of energy in one step, rise in temperature also takes place in respiration. Respiration, happens at the body temperature whereas combustion requires high ignition temperature for burning fuel molecules.

What do you know about “Yawning and Sneezing”?

Yawning: The action of opening one’s mouth wide while taking a long and deep breath of air is called yawning. When we are tired, bored, stressed, over worked, feel sleepy or drowsy, we do not breathe as deeply as we normally do and hence our breathing rate slows down. Due to slower breathing rate, less oxygen goes into our body which is insufficient for respiration. Yawning helps in bringing more oxygen into our blood because during yawning our mouth opens wide and we take a long and deep breathe of air without any control over it.
Sneezing: The sudden expulsion of air from the nose, due to the irritation of nasal passage is called sneezing. When we inhale air, the unwanted particles present in air are usually get trapped in the hair present in our nasal passage and irritate the lining of nasal passage, as a result of which we sneeze. Sneezing expels all the unwanted particles from the inhaled air so that a dust free, clean air enters into our lungs.