Respiration is the process by which living organisms release energy from the food they eat. This energy is necessary for all life activities like movement, growth, and repair. Different organisms use different methods to breathe and get energy. Some use oxygen (aerobic respiration), while others can release energy without oxygen (anaerobic respiration). This chapter Class 7 Science Chapter 9 Respiration in organisms explains how plants, animals, and microbes respire to survive and carry out their daily functions.
Class 7 Science Chapter 9 Respiration in organisms-Textbook Answers
Objective Type Questions
- Fill in the blanks with the correct words:
1. A series of (physical/chemical) reactions result in the release of energy by oxidation of food.
Ans: A series of chemical reactions result in the release of energy by oxidation of food.
2. When the diaphragm…….(contracts/expands) oxygen-rich air is taken into the lungs.
Ans: When the diaphragm contracts, oxygen-rich air is taken into the lungs.
3. The wind pipe is made up of several ring-like structures, held together by ………..(muscles/cartilage).
Ans: The windpipe and pipe is made up of several ring-like structures, held together by cartilage.
4. Plant roots typically take in…………spaces between soil particles and give off.
Ans: Plant roots typically take in oxygen available in small spaces between soil particles and give off carbon dioxide.
5………….. (Aerobic/Anaerobic) respiration is the most efficient form of respiration.
(oxygen/carbon dioxide) available in small (oxygen/carbon dioxide).
Ans: Aerobic respiration is the most efficient form of respiration.
B. Choose the correct option.
1. Which of these are like slits and are made up of thread-like structures?
a. Gills b. Filaments
c. Capillaries d. All of these
Answer: a. Gills
2. Which of these carries the inhaled air into tiny air bags in human beings?
a. Trachea b. Bronchi
c. Bronchioles d. Larynx
Answer: c. Bronchioles
3. Which of these carries oxygenated blood from the lungs to the heart?
a. Bronchus b. Pulmonary artery
c. Pulmonary vein d. Alveoli
Answer: b. Pulmonary vein
4. Which of these is formed as a result of respiration in plants?
a. Energy b. Carbon dioxide
c. Water d. All of these
Answer: d. All of these
5. Which of these is formed as a result of anaerobic respiration?
a. Energy b. Carbon dioxide
c. Energy and ethyl alcohol d. Energy, carbon dioxide, and ethyl alcohol
Answer: d. Energy, carbon dioxide, and ethyl alcohol
6. Which of these refers to breathing?
a. Intake of air rich in oxygen
b. Breakdown of food to produce water and carbon dioxide
c. Releasing energy from the breakdown of food
d. All of these
Answer: a. Intake of air rich in oxygen
7. Which of these do amphibians use to breathe in air on land?
a. Trachea b. Spiracles
c. Surface of the skin d. Lungs
Answer: c. Surface of the skin
8. Which of these helps to pull in oxygen-rich air into the lungs?
a. Expansion of the diaphragm b. Relaxation of the diaphragm
c. Up and down movement of the ribs d. Tracheal tubes
Answer: c. Up and down movement of the ribs
9. Why do farmers plough the soil?
a. To increase root respiration
b. To decrease root respiration
c. To increase respiration through stomata
d. To decrease respiration through stomata
Answer: c. To increase respiration through stomata
10. Which of these is true about anaerobic respiration?
a. It is carried out in humans for a short time.
b. It takes place in our muscle cells when we are doing heavy work or exercise, running fast, etc.
c. It is common in many micro-organisms.
d. All of these
Answer: d. All of these
Class 7 Science Chapter 9 Respiration in organisms- 1 mark
I. Very Short Answer Type Questions:
- Animals in which exchange of gases takes place directly from the water or air through diffusion:
Examples: Earthworm, Hydra - Animals that breathe through spiracles:
Examples: Cockroach, Grasshopper - Animals that breathe through their moist skin as well as their lungs:
Examples: Frog, Salamander - Organisms that respire anaerobically:
Examples: Yeast, Certain bacteria
Class 7 Science Chapter 9 Respiration in organisms- 2 marks
III. Short Answer Type Questions:
- Define respiration. Why is it called a chemical process?
Respiration is the process by which energy is released from the breakdown of food (glucose) in cells. It is a chemical process because it involves chemical reactions that produce new substances and energy. - How does the diaphragm help in pumping air?
The diaphragm contracts and moves downward during inhalation, creating space in the chest cavity for air to enter. It relaxes and moves upward during exhalation, pushing air out of the lungs. - What is oxyhaemoglobin?
Oxyhaemoglobin is the compound formed when oxygen binds with haemoglobin in the red blood cells. It transports oxygen from the lungs to different parts of the body. - Why do roots of plants need to respire?
Roots need to respire because they require energy to perform essential functions. Respiration provides this energy by breaking down glucose using oxygen from the air in the soil. The energy released helps roots absorb water and minerals from the soil, supports their growth, and keeps the root cells alive and functioning properly.
Class 7 Science Chapter 9 Respiration in organisms- 4 marks
IV. Long Answer Type Questions:
1. Explain how a fish respires in water, with the help of gills.
Ans:
Step-by-step Explanation:
- a. Water leaves through gill openings:
After gas exchange, the water flows out through slits behind the gills. - b. Water enters through the fish’s mouth:
The fish opens its mouth to let water flow in. - c. Water passes over the gills:
Gills are located on both sides of the fish’s head. As water flows over them, oxygen dissolved in the water passes into the fish’s blood. - d. Oxygen diffuses into the blood:
The thin walls of the gills allow oxygen to move from the water into the blood vessels in the gills. - e. Carbon dioxide is removed:
At the same time, carbon dioxide (a waste gas) from the fish’s blood passes out into the water through the gills.
2. Describe how exchange of gases takes place inside the human respiratory system.
Ans:
- Breathing In (Inhalation):
- When we breathe in, oxygen from the air enters our nose, passes through the windpipe (trachea), and reaches the lungs.
- Inside the Lungs:
- The lungs have many tiny balloon-like structures called alveoli.
- These alveoli are surrounded by thin blood vessels called capillaries.
- Exchange of Gases:
- Oxygen from the alveoli passes into the blood through the capillaries.
- At the same time, carbon dioxide from the blood moves into the alveoli.
- Breathing Out (Exhalation):
- The carbon dioxide collected in the alveoli is sent out of the body when we breathe out.
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