Science · Class 7
Respiration in Organisms
Aerobic and anaerobic respiration in plants, animals, and yeast.
4 sections15–25 min read6 MCQs · 2 examples
Chapter Overview
All living organisms respire to release energy from food. This chapter covers breathing vs cellular respiration, aerobic and anaerobic pathways, respiration in plants, fish, and earthworms.
Types of Respiration
- Aerobic: with oxygen — complete breakdown of glucose → CO₂ + H₂O + energy (more ATP)
- Anaerobic: without oxygen — partial breakdown (e.g. yeast → alcohol + CO₂; muscles → lactic acid)
- Breathing: intake/release of gases; respiration: cellular process
Respiration in Organisms
- Humans: lungs, alveoli — gas exchange
- Fish: gills extract dissolved oxygen
- Earthworm: moist skin
- Plants: stomata — respire day and night; photosynthesise only in light
Yeast and Muscles
- Yeast anaerobic respiration used in bread and alcohol
- Muscle cramps from lactic acid after heavy exercise
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Compare processes
Distinguish breathing and respiration.
- 1Breathing: physical gas exchange (inhale/exhale)
- 2Respiration: chemical breakdown of glucose in cells
- 3Breathing is part of getting O₂ for respiration
Answer
Breathing is mechanical; respiration is biochemical
Fish respiration
How do fish breathe underwater?
- 1Water passes over gills
- 2Dissolved O₂ absorbed into blood
- 3CO₂ released to water
Answer
Gills extract dissolved oxygen
Key Points to Remember
- ✓ Inhaled air has more O₂ than exhaled
- ✓ Plants respire through stomata
- ✓ Mitochondria site of cellular respiration
Exam Tips
- • Write equation for aerobic respiration
- • Compare aerobic and anaerobic respiration
- • Why do we breathe faster after exercise?
Practice MCQs — Respiration in Organisms
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 6Score: 0/0
Aerobic respiration needs: