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Why Do We Respire?
- Cells: Smallest units of organisms, performing functions like nutrition and excretion.
- Energy: Needed for all activities (eating, sleeping, reading).
- Food: Provides stored energy released during respiration.
- Breathing: Involves taking in oxygen and releasing carbon dioxide.
Cellular Respiration
- Definition: Breakdown of food in cells to release energy.
- Process: Glucose + Oxygen → Carbon Dioxide + Water + Energy.
- Types:
- Aerobic Respiration: Uses oxygen.
- Anaerobic Respiration: Does not use oxygen.
Anaerobic Respiration
- Yeast: Survives without air, producing alcohol and carbon dioxide.
- Muscle Cells: Respire anaerobically during heavy exercise when oxygen is low.
- Muscle Cramps: Caused by lactic acid from partial glucose breakdown.
Relieving Muscle Cramps
- Hot Water Bath or Massage: Improves blood circulation.
- Oxygen Supply: Increased, breaking down lactic acid completely.
Fun Fact
- Yeasts: Single-celled organisms.
- Use: Make wine and beer through anaerobic respiration, producing alcohol.
Key Points
- Respiration provides energy for cells.
- We breathe in oxygen and breathe out carbon dioxide.
- Energy release can be aerobic or anaerobic.
- Muscle cramps are due to anaerobic respiration.
Breathing
Activity 6.1: Holding Your Breath
- Try This: Close your nostrils and mouth tightly. Check how long you can hold your breath.
- Observation: You can’t survive long without breathing.
What is Breathing?
- Breathing: Taking in oxygen-rich air (inhalation) and giving out carbon dioxide-rich air (exhalation).
- Continuous Process: Goes on all the time, throughout life.
Breathing Rate
- Definition: Number of breaths (inhalation + exhalation) per minute.
- Measurement: You can count your breaths in a minute to find your breathing rate.
Activity 6.2: Measuring Breathing Rate
- Steps:
- Count breaths (inhalations and exhalations) in a minute.
- Note the breathing rate after walking, running, and resting.
- Compare with classmates.
- Observation: Faster breathing when more energy is needed (e.g., after exercise).
Breathing and Energy
- Extra Energy Needs: Faster breathing supplies more oxygen to cells, speeding up food breakdown and energy release.
- Hunger After Exercise: Explained by the increased energy demand and faster food breakdown.
Breathing Rate Changes
- Rest: Average adult breathes 15–18 times per minute.
- Exercise: Breathing rate can increase up to 25 times per minute. Deep breaths bring in more oxygen.
- Drowsiness: Breathing rate slows down, potentially reducing oxygen supply.
Activity 6.3: Breathing Rate in Different Activities
- Task: Look at various activities and determine where breathing rate is slowest and fastest.
- Order Activities: Rank activities by breathing rate based on your experience.
Key Points
- Breathing involves inhalation and exhalation.
- Breathing rate changes with activity levels.
- Faster breathing provides more oxygen, releasing more energy.
How Do We Breathe?
Mechanism of Breathing
- Inhalation:
- Air enters through nostrils into the nasal cavity.
- Passes through the windpipe to the lungs.
- Lungs are in the chest cavity, surrounded by ribs and the diaphragm.
- Ribs move up and out, diaphragm moves down, increasing chest space.
- Air rushes into the lungs.
- Exhalation:
- Ribs move down and in, diaphragm moves up.
- Chest space reduces.
- Air is pushed out of the lungs.
Activity 6.4: Measuring Chest Expansion
- Task: Measure chest size before and after deep breaths with a measuring tape.
- Observation: Note the chest expansion among classmates.
Breathing Model (Activity 6.5)
- Materials: Plastic bottle, Y-shaped tube, balloons, rubber sheet.
- Steps:
- Remove the bottom of the bottle, insert the tube with balloons inside.
- Seal the bottle, tie a rubber sheet at the open base.
- Inhale Simulation: Pull rubber sheet down, balloons inflate.
- Exhale Simulation: Push rubber sheet up, balloons deflate.
- Representation:
- Balloons represent lungs.
- Rubber sheet represents the diaphragm.
What do we breathe out?
Breathing Out (Activity 6.6)
- Task: Blow air into lime water using a straw.
- Observation: Lime water turns milky.
- Explanation: Shows presence of carbon dioxide in exhaled air.
Fun Facts and Tips
- Smoking: Damages lungs and is linked to cancer.
- Sneezing: Traps and expels unwanted particles from inhaled air.
- Breathing Exercise (Pranayama): Increases lung capacity and oxygen supply.
Air Composition
- Inhaled Air: 21% oxygen, 0.04% carbon dioxide.
- Exhaled Air: 16.4% oxygen, 4.4% carbon dioxide.
Key Points
- Breathing involves rib and diaphragm movements.
- Inhalation increases chest cavity space; exhalation decreases it.
- Exhaled air contains more carbon dioxide and less oxygen.
Breathing in Other Animals
Animals with Lungs
- Examples: Elephants, lions, cows, goats, frogs, lizards, snakes, birds.
- Similar to Humans: Have lungs in their chest cavities.
Breathing in Different Organisms
Cockroach
- Spiracles: Small openings on the sides of the body.
- Tracheae: Network of air tubes for gas exchange.
- Process:
- Oxygen enters through spiracles into tracheal tubes.
- Diffuses into body tissues.
- Carbon dioxide exits through spiracles.
Earthworm
- Skin Breathing: Breathes through moist, slimy skin.
- Gas Exchange: Gases pass through the skin easily.
Frog
- Dual Breathing:
- Lungs: Similar to humans.
- Skin: Moist and slippery for additional breathing.
Breathing Under Water
Fish
- Gills: Help use oxygen dissolved in water.
- Structure: Projections of skin well supplied with blood vessels for gas exchange.
Do Plants Also Respire?
Plant Respiration
- Oxygen Intake: From the air, releasing carbon dioxide.
- Process: Oxygen breaks down glucose into carbon dioxide and water.
- Independence: Each part of the plant breathes independently.
Leaf Respiration
- Stomata: Tiny pores for gas exchange.
Root Respiration
- Oxygen Intake: From air spaces between soil particles.
- Overwatering Effect: Reduces air spaces, hindering root respiration.
Key Points
- Respiration is essential for all living organisms.
- Different organisms have various mechanisms for breathing.
- Plants respire through all their parts, including roots and leaves.
Chapter Summary:
- Respiration is essential for the survival of living organisms.
- Respiration releases energy from food.
- Oxygen we inhale breaks down glucose into carbon dioxide and water.
- Energy is released during this process.
- Breakdown of glucose happens in the cells (cellular respiration).
- With oxygen, it is called aerobic respiration.
- Without oxygen, it is called anaerobic respiration.
- During heavy exercise, muscles use anaerobic respiration due to low oxygen.
- Breathing is part of respiration, taking in oxygen and releasing carbon dioxide.
- Respiratory organs for gas exchange differ in various organisms.
- During inhalation, lungs expand and return to the original state during exhalation.
- Physical activity increases the breathing rate.
- Animals like cows, buffaloes, dogs, and cats have similar respiratory organs and breathing processes as humans.
- In earthworms, gas exchange occurs through moist skin.
- In fishes, gas exchange happens through gills.
- In insects, gas exchange occurs through tracheae.
- In plants, roots take in air from the soil.
- Leaves have stomata for gas exchange.
- Breakdown of glucose in plant cells is similar to that in other living beings.
Keywords
| Serial No. | Keywords | Serial No. | Keywords |
|---|---|---|---|
| 1 | Aerobic respiration | 7 | Gills |
| 2 | Anaerobic respiration | 8 | Lungs |
| 3 | Breathing rate | 9 | Inhalation |
| 4 | Cellular respiration | 10 | Spiracles |
| 5 | Diaphragm | 11 | Tracheae |
| 6 | Exhalation | 12 | Ribs |
