By Subhash Kumar | Science Educator | UREducator
Published: | Updated:
Generate Customized PDF
Get a printer-friendly version of this complete lesson plan
Respiration in Organisms
Complete Teaching Resource for CBSE Class 7 Science Chapter 6
Class: VII
Subject: Science
Chapter: 6
Duration: 4 Hours
What Students Will Achieve
Knowledge
- Define respiration and explain its importance
- Differentiate between aerobic and anaerobic respiration
- Describe the human breathing mechanism
- Identify respiratory organs in different organisms
Understanding
- Explain why breathing rate increases during exercise
- Analyze how different organisms adapt for respiration
- Understand the role of respiration in energy production
- Explain the causes and effects of muscle cramps
Skills
- Measure and compare breathing rates
- Construct models of respiratory systems
- Demonstrate gas exchange in respiration
- Compare respiratory adaptations across species
Prior Knowledge Assessment
Starter Questions:
- Why do we breathe faster after running?
- What gas do we exhale during breathing?
- How do fish breathe underwater?
The Energy Release Process
Types of Respiration
Aerobic Respiration
(With oxygen)
- Complete breakdown of glucose
- Produces CO2, H2O and 38 ATP
- Occurs in mitochondria
- Equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
Anaerobic Respiration
(Without oxygen)
- Partial breakdown of glucose
- Produces lactic acid (animals) or alcohol+CO2 (yeast)
- Only 2 ATP produced
- Emergency energy source
Why Breathing Rate Increases During Exercise
| Factor | Effect | Result |
|---|---|---|
| Energy Demand | Muscles need more ATP | Faster cellular respiration |
| Oxygen Need | More oxygen required | Increased breathing rate |
| CO2 Production | More waste CO2 generated | Faster removal needed |
| Oxygen Shortage | Temporary deficit | Anaerobic respiration in muscles |
Experiment: Measuring Breathing Rate
Objective: Demonstrate how activity level affects breathing
- Measure resting breathing rate (breaths per minute)
- Walk briskly for 2 minutes, measure immediately after
- Run for 1 minute, measure immediately after
- Rest for 5 minutes, measure again
- Compare results and explain the differences
The Human Respiratory System
Key Components
Air Passage
- Nostrils → Nasal cavity → Pharynx → Trachea
- Trachea branches into bronchi → bronchioles
- Ends in alveoli (air sacs)
- Mucus and cilia filter air
Lungs
- Spongy, elastic organs in chest cavity
- Right lung (3 lobes), Left lung (2 lobes)
- Contain ~300 million alveoli
- Surface area ~75m2 (tennis court size)
Breathing Muscles
- Diaphragm: Dome-shaped muscle below lungs
- Intercostal muscles between ribs
- Work together to change chest volume
- Create pressure differences for air flow
Breathing Mechanism
| Process | Muscle Action | Chest Changes | Air Movement |
|---|---|---|---|
| Inhalation | Diaphragm contracts (flattens) Rib muscles contract |
Chest cavity expands Volume increases |
Air rushes in (lower pressure) |
| Exhalation | Diaphragm relaxes (domes up) Rib muscles relax |
Chest cavity shrinks Volume decreases |
Air pushed out (higher pressure) |
Activity: Lung Model Construction
Objective: Demonstrate how lungs work using a bottle model
- Cut bottom off a plastic bottle (chest cavity)
- Attach balloon to straw (lung)
- Insert straw through bottle neck
- Stretch rubber sheet over bottle bottom (diaphragm)
- Pull sheet down to "inhale" (balloon inflates)
- Push sheet up to "exhale" (balloon deflates)
Respiratory Adaptations Across Species
Comparative Respiratory Systems
Fish (Gills)
- Extract oxygen from water
- Rich blood supply in gill filaments
- Counter-current flow maximizes O2 uptake
- Operculum protects gills
Insects (Tracheae)
- Network of air tubes throughout body
- Enter through spiracles (openings)
- Direct oxygen delivery to tissues
- No blood involvement in gas transport
Earthworms (Skin)
- Moist skin allows gas exchange
- Capillaries close to skin surface
- Mucus maintains moisture
- Dies if skin dries out
Frogs (Multiple)
- Lungs (simple sacs)
- Moist skin (especially in water)
- Buccal cavity breathing
- Adapt based on environment
Plant Respiration
| Feature | Description | Adaptations |
|---|---|---|
| Gas Exchange | Occurs in all living cells | Stomata in leaves, lenticels in stems |
| Root Respiration | Oxygen from air spaces in soil | Root hairs increase surface area |
| Day vs Night | Respiration continues 24/7 | Photosynthesis masks respiration during day |
Project: Comparing Respiratory Systems
Objective: Research and present different respiratory adaptations
- Choose an organism (fish, insect, amphibian, etc.)
- Research its respiratory system
- Create a labeled diagram
- Explain adaptations to its environment
- Compare to human respiratory system
- Present findings to class
Evaluation Strategies
Formative Assessments
- Labeling respiratory system diagrams
- Breathing rate experiment reports
- Class discussions on respiration scenarios
- Quiz on aerobic vs anaerobic respiration
Summative Assessments
- Chapter test (MCQs + short answers)
- Model building and demonstration
- Case study on athlete's breathing
- Research project on animal adaptations
Extended Learning: Visit to Aquarium
Objective: Observe fish respiration and adaptations
- Count operculum movements (breathing rate)
- Compare different fish species
- Observe gill structures in display models
- Interview aquarium staff about water oxygenation
- Prepare a comparative report
Frequently Asked Questions
Why do we get muscle cramps after heavy exercise?
Muscle cramps occur because:
- During intense exercise, oxygen supply can't meet demand
- Muscles switch to anaerobic respiration
- Lactic acid builds up as a byproduct
- Accumulated lactic acid causes pain and cramps
- Massage or hot bath improves circulation to remove lactic acid
How do whales and dolphins breathe if they live in water?
Marine mammals have special adaptations:
- They have lungs like land mammals (not gills)
- Must surface regularly to breathe air
- Blowholes on top of head act as nostrils
- Can store more oxygen in blood and muscles
- Slow heart rate during dives to conserve oxygen
