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Practice Class 7 Science Chapter 10 Respiration in Organisms MCQ Questions with Answers based on the latest NCERT syllabus. Learn about stomata, cellular respiration, earthworm respiration, lactic acid, and spiracles with detailed explanations, exam tips, and original NCERT-based solutions for CBSE and State Board students.
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Chapter Information
Subject: Science
Class: 7
Chapter: Respiration in Organisms
Question Type: Multiple Choice Questions (MCQs)
Difficulty Level: Easy to Moderate
Based On: Latest NCERT Syllabus
Introduction
Respiration is an essential life process through which living organisms obtain energy from food. Plants, animals, and microorganisms have different methods of exchanging gases and carrying out respiration. Understanding these processes helps students learn how living organisms survive, grow, and perform daily activities. This practice set focuses on important NCERT concepts related to respiration and energy release.
What You Will Learn
✔ Exchange of gases in plants
✔ Cellular respiration
✔ Respiration in earthworms
✔ Cause of muscle cramps
✔ Respiratory organs of insects
✔ Important NCERT concepts
Why This Topic Is Important?
Respiration is one of the most important biological processes. Questions from this chapter are frequently asked in CBSE, State Board, Olympiad, and scholarship examinations. A clear understanding of respiration also helps students relate science to everyday activities such as exercise, breathing, and plant life.
Exam Relevance
These questions are useful for:
✔ CBSE Exams
✔ State Board Exams
✔ School Tests
✔ Unit Tests
✔ Half-Yearly Exams
✔ Annual Exams
✔ Olympiad Preparation
✔ Scholarship Examinations
Q1. In plants, the exchange of gases takes place through:
A) Stomata
B) Flowers
C) Stem
D) Roots
Answer
Stomata
Concept Behind This Question
Plants exchange gases through tiny openings present mainly on the surface of their leaves.
Step-by-Step Solution
Stomata are small pores found mostly on the lower surface of leaves. They allow:
- Oxygen to enter the plant.
- Carbon dioxide to leave or enter depending on the process.
- Water vapour to escape during transpiration.
Flowers, stems, and roots have other functions, but the main gas exchange in plants occurs through stomata.
Therefore, the correct answer is: Stomata.
Exam Tip
Remember:
Plants → Gas Exchange → Stomata
Q2. The process of breakdown of food in the cell with the release of energy is called:
A) Digestion
B) Cellular respiration
C) External respiration
D) Photosynthesis
Answer
Cellular respiration
Concept Behind This Question
Cells release energy from food through a chemical process called cellular respiration.
Step-by-Step Solution
In cellular respiration:
- Food (especially glucose) is broken down inside cells.
- Energy is released for life processes.
- Carbon dioxide and water are produced during aerobic respiration.
Digestion breaks food into simpler substances, while photosynthesis prepares food in green plants.
Therefore, the correct answer is: Cellular respiration.
Exam Tip
Remember:
Food + Oxygen → Energy + Carbon Dioxide + Water
Q3. Earthworms breathe through their:
A) Gills
B) Spiracles
C) Lungs
D) Skin
Answer
Skin
Concept Behind This Question
Different animals have different respiratory organs.
Step-by-Step Solution
Earthworms do not possess lungs or gills.
Their moist skin allows oxygen to diffuse into the body while carbon dioxide diffuses out.
Keeping the skin moist is essential for their respiration.
Therefore, the correct answer is: Skin.
Exam Tip
Remember:
- Earthworm → Skin
- Fish → Gills
- Humans → Lungs
- Insects → Spiracles
Q4. During heavy exercise, we get cramps in the legs due to the accumulation of:
A) Lactic acid
B) Water
C) Carbon dioxide
D) Alcohol
Answer
Lactic acid
Concept Behind This Question
When muscles do not receive enough oxygen during vigorous activity, they perform anaerobic respiration.
Step-by-Step Solution
During heavy exercise:
- The oxygen supply to muscles may become insufficient.
- Muscles temporarily undergo anaerobic respiration.
- This leads to the formation of lactic acid, which may cause muscle cramps and fatigue.
After rest, the body gradually removes the excess lactic acid.
Therefore, the correct answer is: Lactic acid.
Exam Tip
Remember:
Heavy Exercise → Less Oxygen → Lactic Acid → Muscle Cramps
Q5. The tiny openings on the sides of an insect’s body are called:
A) Spiracles
B) Trachea
C) Gills
D) Lungs
Answer
Spiracles
Concept Behind This Question
Insects breathe through a system of air tubes connected to openings on their body.
Step-by-Step Solution
Tiny openings called spiracles are present on the sides of an insect’s body.
Air enters through these spiracles and travels through branching tubes called the tracheal system to different parts of the body.
Therefore, the correct answer is: Spiracles.
Exam Tip
Remember:
Insects → Spiracles → Tracheal System
Important Formulas & Concepts
1. Respiration
Respiration is the process by which food is broken down to release energy for life activities.
2. Cellular Respiration
Food + Oxygen → Energy + Carbon Dioxide + Water
This process takes place inside cells.
3. Gas Exchange in Plants
Plants exchange gases mainly through stomata, which are tiny pores present on leaves.
4. Respiration in Different Organisms
| Organism | Respiratory Organ |
| Humans | Lungs |
| Fish | Gills |
| Earthworm | Skin |
| Insects | Spiracles |
5. Anaerobic Respiration
When oxygen is insufficient, muscles produce energy through anaerobic respiration, leading to the formation of lactic acid.
6. Spiracles
Spiracles are tiny openings on the sides of an insect’s body that allow air to enter the tracheal system.
Related Practice Questions
- What is the difference between breathing and respiration?
- Why must the skin of an earthworm remain moist?
- What is the function of stomata in plants?
- Why do muscles produce lactic acid during heavy exercise?
- How does the tracheal system help insects breathe?
Mini Quiz Challenge
True or False
- Plants exchange gases mainly through stomata.
- Cellular respiration releases energy from food.
- Earthworms breathe through lungs.
- Lactic acid may accumulate during heavy exercise.
- Insects breathe through spiracles.
Exam Tips
✔ Learn the respiratory organs of different organisms.
✔ Understand the difference between breathing and cellular respiration.
✔ Revise the role of stomata in plants.
✔ Remember the cause of muscle cramps.
✔ Practice examples of aerobic and anaerobic respiration.
Quick Revision Notes
✔ Plants exchange gases through stomata.
✔ Cellular respiration releases energy from food.
✔ Earthworms breathe through moist skin.
✔ Lactic acid causes muscle cramps during heavy exercise.
✔ Insects breathe through spiracles.
✔ Spiracles are connected to the tracheal system.
Common Mistakes Students Make
❌ Confusing breathing with cellular respiration.
❌ Thinking earthworms breathe through lungs.
❌ Mixing up spiracles and trachea.
❌ Assuming plants exchange gases through roots only.
❌ Believing lactic acid is produced during normal breathing.
Key Takeaways
- Stomata are the main sites of gas exchange in plants.
- Cellular respiration releases energy required for life processes.
- Earthworms exchange gases through their moist skin.
- Lactic acid may accumulate in muscles during strenuous exercise.
- Insects breathe through spiracles connected to the tracheal system.
FAQs
1. Through which structure do plants exchange gases?
Plants mainly exchange gases through stomata present on their leaves.
2. What is cellular respiration?
Cellular respiration is the process in which food is broken down inside cells to release energy.
3. How do earthworms breathe?
Earthworms breathe through their moist skin, which allows gases to diffuse.
4. Why do muscle cramps occur during heavy exercise?
Muscle cramps may occur because lactic acid accumulates when muscles temporarily receive insufficient oxygen.
5. What are spiracles?
Spiracles are tiny openings on the sides of an insect’s body through which air enters the tracheal system.
Conclusion
This Class 7 Science MCQ Practice Set covers the key concepts of Respiration in Organisms, including stomata, cellular respiration, respiration in earthworms, lactic acid formation, and spiracles. Regular practice of these NCERT-based questions strengthens conceptual understanding, improves scientific reasoning, and helps students perform confidently in school examinations and competitive tests.
NCERT Reference
Book: NCERT Science Class 7
Chapter: Chapter 10 – Respiration in Organisms
Based On: Latest NCERT Curriculum (CBSE)
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