CBSE Class 7 Science Exemplar Chapter 10: Respiration in Organisms NCERT Solutions
This resource provides comprehensive NCERT Solutions for CBSE Class 7 Science Exemplar, focusing on Chapter 10: Respiration in Organisms. It covers essential concepts such as the difference between aerobic and anaerobic respiration, the process of breathing in humans, and how aquatic animals like fish respire. The solutions explain the role of muscle cells during heavy exercise, the function of yeast in fermentation, and the mechanics of exhalation. Understanding these processes is crucial for grasping how living beings obtain energy and manage gas exchange. These solutions are designed to help students clarify doubts, reinforce their learning, and prepare effectively for their examinations by offering clear, step-by-step explanations for each question.
Quick info
| Board | CBSE |
|---|---|
| Class | Class 7 |
| Subject | Science Exemplar |
| Session | 2026 |
| Language | English |
| Type | NCERT Solutions |
| Chapter | Chapter 10 |
Chapter summary
Chapter 10 of the CBSE Class 7 Science Exemplar, 'Respiration in Organisms,' delves into the fundamental processes of how different living beings respire. The NCERT Solutions cover multiple-choice questions that explore aerobic and anaerobic respiration, the physiological mechanisms of breathing in humans, and the specialized respiratory organs of aquatic animals like fish. This chapter highlights the energy release mechanisms and gas exchange vital for life.
Learning outcomes
- Understand the process of aerobic and anaerobic respiration.
- Identify the products of anaerobic respiration in muscle cells and yeast.
- Explain the mechanics of exhalation in humans.
- Describe how fish respire using gills.
- Differentiate between the functions of breathing and cellular respiration.
Topics covered
Paper topics
- Respiration in Organisms
- Aerobic Respiration
- Anaerobic Respiration
- Muscle Respiration during Exercise
- Yeast Respiration
- Breathing Process in Humans
- Exhalation Mechanics
- Respiration in Fish
- Gills Function
- Gas Exchange
Important topics
- Aerobic vs. Anaerobic Respiration
- Products of Anaerobic Respiration
- Mechanism of Breathing
- Respiration in Aquatic Animals
PDF preview
Read page by page below. PDF is streamed from the official NCERT website — no download button on this page.
Questions and Solutions
Multiple Choice Questions
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
Explanation: During strenuous physical activity, our muscle cells may not receive sufficient oxygen to perform aerobic respiration. In such conditions, they switch to anaerobic respiration. This process breaks down glucose in the absence of oxygen to produce lactic acid and a small amount of energy. The accumulation of lactic acid in the muscles is responsible for the feeling of fatigue and soreness experienced after intense exercise.
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.
Explanation: Yeast is a type of fungus that can perform both aerobic and anaerobic respiration. In the absence of oxygen (anaerobic conditions), yeast breaks down sugars like glucose through a process called fermentation. This fermentation produces ethanol (alcohol) and carbon dioxide. This property makes yeast extremely valuable in the wine and beer industries for producing alcoholic beverages.
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.
Explanation: Exhalation is the process of releasing air from the lungs. During exhalation, the diaphragm, a large muscle below the lungs, relaxes and moves upwards. Simultaneously, the external intercostal muscles relax, causing the rib cage to move downwards and inwards. These movements decrease the volume of the chest cavity, which increases the pressure inside the lungs, forcing the air out.
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)
Explanation: Breathing is the physical process of ventilation, involving the intake of oxygen-rich air and the expulsion of carbon dioxide-rich air. Therefore, its primary functions are to supply the body with oxygen (i) and to remove carbon dioxide from the body (iii). The breakdown of food to release energy (ii) and the production of water in cells (iv) are part of cellular respiration, which occurs inside the cells and utilizes the oxygen obtained through breathing.
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.
Explanation: Fish live in water and respire using gills. Gills are specialized organs with a large surface area and a rich supply of blood capillaries. As water passes over the gills, dissolved oxygen from the water diffuses into the blood, and carbon dioxide diffuses out of the blood into the water. This process allows fish to efficiently obtain oxygen from their aquatic environment.
Common mistakes
- Confusing the products of anaerobic respiration in different organisms.
- Misunderstanding the direction of rib movement during exhalation.
- Confusing breathing (gas exchange) with cellular respiration (energy release).
Revision tips
- Focus on the by-products of anaerobic respiration in muscle cells and yeast.
- Visualize the movement of ribs and diaphragm during breathing.
- Compare and contrast the respiratory mechanisms of humans and fish.
- Review the definitions of aerobic and anaerobic respiration.
Practice MCQs
Q1. During strenuous physical activity, what substance is primarily produced in our muscle cells when anaerobic respiration occurs?
Explanation: When oxygen supply is insufficient during heavy exercise, muscle cells resort to anaerobic respiration, breaking down glucose to produce lactic acid and a small amount of energy. This lactic acid accumulation can cause muscle fatigue.
Q2. Yeast is industrially significant in the production of wine and beer primarily because of its ability to perform which type of respiration?
Explanation: Yeast undergoes anaerobic respiration in the absence of oxygen, converting sugars into ethanol (alcohol) and carbon dioxide. This process, known as fermentation, is fundamental to the alcoholic beverage industry.
Q3. What is the movement of the ribs during the process of exhalation?
Explanation: During exhalation, the muscles contract, causing the rib cage to move downwards and inwards. Simultaneously, the diaphragm relaxes and moves upwards, reducing the volume of the chest cavity and forcing air out of the lungs.
Q4. Breathing is a vital biological process. Which of the following accurately describes its main functions?
Explanation: Breathing is the physical process of gas exchange. Its primary functions are to take in oxygen from the atmosphere and expel carbon dioxide from the body. The breakdown of food for energy occurs through cellular respiration, which uses the oxygen obtained from breathing.
Q5. Fish possess gills, which are rich in blood vessels. What is the main function of these gills for the fish?
Explanation: Gills are specialized respiratory organs in fish that are highly efficient at extracting dissolved oxygen from the water as it passes over them. They also facilitate the release of carbon dioxide.
Frequently asked questions
What is the main difference between aerobic and anaerobic respiration?
Aerobic respiration occurs in the presence of oxygen and produces a large amount of energy, carbon dioxide, and water. Anaerobic respiration occurs in the absence of oxygen and produces less energy along with substances like lactic acid or alcohol and carbon dioxide.
What happens in our muscle cells during heavy exercise?
During heavy exercise, our muscle cells may not get enough oxygen. They then perform anaerobic respiration, breaking down glucose to produce lactic acid and energy. This lactic acid can cause muscle cramps.
How do fish breathe?
Fish breathe using gills, which are specialized organs that extract dissolved oxygen from the water as it flows over them. Gills are rich in blood vessels to facilitate efficient gas exchange.
What is the role of yeast in industries like wine and beer production?
Yeast is used because it can perform anaerobic respiration (fermentation). In this process, it converts sugars into alcohol (ethanol) and carbon dioxide, which are essential for making alcoholic beverages.
What are the key actions of the ribs and diaphragm during exhalation?
During exhalation, the ribs move down and inwards, and the diaphragm moves upwards. This reduces the volume of the chest cavity, increasing pressure and forcing air out of the lungs.
Content reviewed by the NCERT Help team. Editorial Team and update policy
NCERT Solutions PDF PDF on NCERT Help. URL unchanged for search indexing.