Respiration in Organisms – Class 7 Science Notes and Questions Answers
Introduction: Respiration is one of the most essential biological processes. Every living organism, whether plant or animal, requires energy to perform daily activities such as growth, repair, movement, and reproduction. This energy is released through the process of respiration. In Class 7 Science, the chapter “Respiration in Organisms” helps us understand the types of respiration, the role of oxygen, the process in humans and other animals, and the importance of breathing. Below you will find detailed NCERT notes and a complete set of questions and answers designed for exams, NCERT learning, and concept clarity.
📘 Notes – Respiration in Organisms
1. What is Respiration?
Respiration is the biological process by which living organisms break down food molecules (like glucose) to release energy. This energy is used for all life activities.
2. Types of Respiration
- Aerobic Respiration: Takes place in the presence of oxygen. Food is completely broken down into carbon dioxide and water. It releases a large amount of energy.
- Anaerobic Respiration: Takes place in the absence of oxygen. Food is partially broken down into substances such as alcohol or lactic acid. It releases less energy compared to aerobic respiration.
3. Breathing vs Respiration
- Breathing: The physical process of inhaling oxygen and exhaling carbon dioxide.
- Respiration: The chemical process of breaking down glucose inside the cells to release energy.
4. Human Respiratory System
The main organs of the human respiratory system include the nose, trachea, lungs, and diaphragm. The air we inhale passes through the nose, windpipe, and bronchi before reaching the lungs, where gaseous exchange occurs.
5. Process of Breathing in Humans
- Inhalation: The diaphragm contracts and moves downward, creating space in the chest cavity. Air rich in oxygen enters the lungs.
- Exhalation: The diaphragm relaxes and moves upward, pushing air rich in carbon dioxide out of the lungs.
6. Breathing in Animals
- Earthworms: Breathe through moist skin.
- Fish: Use gills to extract oxygen from water.
- Insects: Have spiracles (tiny holes) on their body surface for respiration.
- Amphibians (like frogs): Use both lungs and skin.
7. Cellular Respiration
This is the process of breaking down glucose inside the cell’s mitochondria to release energy in the form of ATP (Adenosine Triphosphate). It is a continuous process required for survival.
8. Importance of Respiration
- Provides energy for growth and repair.
- Enables movement and locomotion.
- Supports life processes such as digestion, circulation, and excretion.
- Maintains balance of gases in the environment.
✍️ Questions and Answers – Respiration in Organisms
📝 Multiple Choice Questions (7)
Q1: Respiration is a process that:
- Releases oxygen
- Releases energy
- Consumes carbon dioxide
- Produces proteins
Answer: (b) Releases energy
Q2: The site of cellular respiration is:
- Nucleus
- Chloroplast
- Mitochondria
- Vacuole
Answer: (c) Mitochondria
Q3: Which of the following organisms breathe through their skin?
- Frogs
- Birds
- Humans
- Cows
Answer: (a) Frogs
Q4: Which gas is released during respiration?
- Oxygen
- Carbon dioxide
- Nitrogen
- Hydrogen
Answer: (b) Carbon dioxide
Q5: The energy released in respiration is stored in:
- DNA
- ATP
- RNA
- Chlorophyll
Answer: (b) ATP
Q6: In anaerobic respiration in muscles, glucose is converted into:
- Alcohol and CO2
- Lactic acid
- Water and CO2
- None
Answer: (b) Lactic acid
Q7: The breathing rate of a person increases during:
- Sleep
- Exercise
- Rest
- Meditation
Answer: (b) Exercise
📝 Very Short Answer Questions (7)
Q1: Define breathing.
Answer: The process of inhaling oxygen and exhaling carbon dioxide is called breathing.
Q2: Name the muscle that helps in breathing.
Answer: Diaphragm.
Q3: Which gas is essential for respiration?
Answer: Oxygen.
Q4: What is the respiratory organ of fish?
Answer: Gills.
Q5: Where does gaseous exchange occur in humans?
Answer: In the alveoli of the lungs.
Q6: Which type of respiration releases more energy?
Answer: Aerobic respiration.
Q7: Name the organism that respires through spiracles.
Answer: Insects (e.g., grasshopper).
📝 Short Answer Questions (7)
Q1: Differentiate between aerobic and anaerobic respiration.
Answer: Aerobic respiration occurs in the presence of oxygen and produces CO2, water, and large energy. Anaerobic respiration occurs without oxygen and produces less energy along with alcohol or lactic acid.
Q2: Why does our breathing rate increase during exercise?
Answer: During exercise, muscles require more energy. To meet this demand, oxygen intake increases, causing faster breathing.
Q3: Explain why anaerobic respiration is less efficient.
Answer: Anaerobic respiration partially breaks down glucose, releasing less energy compared to complete breakdown in aerobic respiration.
Q4: How do plants respire?
Answer: Plants respire through stomata in leaves and lenticels in stems, taking in oxygen and releasing carbon dioxide.
Q5: What causes muscle cramps during intense exercise?
Answer: Lack of oxygen leads to anaerobic respiration in muscles, producing lactic acid which causes cramps.
Q6: Why is mitochondria called the powerhouse of the cell?
Answer: Because mitochondria are the site where glucose is broken down to release energy in the form of ATP.
Q7: State two functions of the diaphragm.
Answer: Helps in inhalation by contracting and creating space, and aids exhalation by relaxing and reducing chest cavity space.
📝 Long Answer Questions (7)
Q1: Describe the human respiratory system with a labeled explanation.
Answer: The human respiratory system consists of the nose, trachea, bronchi, lungs, and diaphragm. Air enters through the nose, passes into the trachea, then bronchi, and finally reaches alveoli in the lungs where gaseous exchange occurs. Oxygen diffuses into blood, and carbon dioxide diffuses out.
Q2: Explain the process of cellular respiration.
Answer: Cellular respiration is the breakdown of glucose in cells to release energy. In aerobic respiration, glucose + oxygen → carbon dioxide + water + energy. In anaerobic respiration, glucose → lactic acid/alcohol + less energy. It occurs in mitochondria.
Q3: Discuss the difference between breathing and respiration.
Answer: Breathing is a physical process involving inhalation and exhalation, while respiration is a biochemical process in which glucose is broken down inside cells to release energy. Breathing is external, respiration is cellular.
Q4: Explain respiration in fish.
Answer: Fish use gills for respiration. Water enters the mouth, passes over gills, and oxygen is absorbed into blood while carbon dioxide is expelled. This adaptation allows them to survive in aquatic habitats.
Q5: Why is respiration essential for life?
Answer: Respiration provides the energy needed for all vital processes like growth, repair, reproduction, locomotion, and maintaining body functions. Without respiration, cells cannot survive.
Q6: Write a note on anaerobic respiration in yeast and humans.
Answer: In yeast, anaerobic respiration breaks down glucose to alcohol, carbon dioxide, and energy. In humans, it produces lactic acid and energy. Yeast fermentation is used in baking and brewing, while lactic acid accumulation causes muscle fatigue.
Q7: Explain how different organisms adapt for respiration.
Answer: Earthworms respire through moist skin, insects through spiracles and tracheae, fish through gills, amphibians like frogs through lungs and skin, while mammals rely on lungs. These adaptations suit their habitats.
Conclusion: Respiration is the fundamental life process that ensures the release of energy from food. Without respiration, life cannot exist. From unicellular organisms to humans, every organism has developed its own way of breathing and respiration. This chapter is not only important for exams but also for understanding how life sustains itself.
Related Reading: Explore More Class 7 Science Chapters
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