Respiration in Organisms Class 7 Free Notes and Mind Map (Free PDF Download)

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respiration

Respiration enables energy release from food through cellular mechanisms. Breathing mechanics, including inhalation and exhalation, and diverse respiratory adaptations in animals, such as gills for aquatic organisms and tracheal systems in insects, are examined. Plant respiration, utilizing stomata and root air spaces, is also covered, providing a concise understanding of gas exchange across living systems

Why Is Respiration Necessary?

  • Respiration is a fundamental biological process that enables living organisms to derive energy from food. This energy is essential for sustaining life functions.
  • Cells require energy for vital processes like nutrient absorption, material transport, waste elimination, and reproduction.
  • Respiration is the mechanism by which energy is extracted from food sources.
  • Inhalation brings oxygen into the body, which is then transported to cells.
  • Within cells, oxygen facilitates the breakdown of food, releasing energy through cellular respiration.
  • Cellular respiration is a universal process in all living organisms.
  • The breakdown of glucose in the presence of oxygen within cells yields carbon dioxide, water, and energy.

The Process of Breathing

  • Breathing is the act of inhaling oxygen-rich air and exhaling carbon dioxide-rich air, facilitated by respiratory organs. It is a continuous, vital function. Breathing is a component of the broader process of respiration.
  • Inhalation: The intake of oxygen-rich air.
    • The rib cage expands upward and outward.
    • The diaphragm contracts and moves downward.
    • This increases chest cavity volume, drawing air into the lungs.
  • Exhalation: The expulsion of carbon dioxide-rich air.
    • The rib cage contracts downward and inward.
    • The diaphragm relaxes and moves upward.
    • This decreases chest cavity volume, forcing air out of the lungs.
  • Respiratory Rate: The frequency of breaths per minute.
    • Varies based on the body’s oxygen demand.
    • A resting adult typically breathes 15–18 times per minute, increasing to 25 times during strenuous activity.
  • Mechanism:
    • Air enters through the nostrils.
    • Passes through the nasal passages.
    • Reaches the lungs via the trachea.
    • The lungs are housed within the rib cage, with the diaphragm forming the base.
  • The air exchanged during breathing is a mixture of gases, not solely oxygen or carbon dioxide. Moisture is visible when exhaling onto a cold surface.

HOW DO WE BREATHE?

  • The breathing process involves air intake through the nostrils, passage through the nasal cavity, and delivery to the lungs via the windpipe. The lungs reside within the chest cavity, bordered by the rib cage and diaphragm.
  • Inhalation:
    • Ribs expand, and the diaphragm descends.
    • This creates more space in the chest cavity, pulling air into the lungs.
  • Exhalation:
    • Ribs contract, and the diaphragm ascends.
    • This reduces chest cavity volume, expelling air from the lungs.
  • Chest cavity volume fluctuates during breathing.
  • Airborne particles like smoke, dust, and pollen are filtered by nasal hairs during inhalation.

WHAT DO WE BREATHE OUT?

  • Exhaled air is a combination of gases, not just carbon dioxide.
  • During exhalation:
    • Ribs contract.
    • The diaphragm rises.
    • Chest cavity volume decreases.
    • Air is expelled from the lungs.

BREATHING IN OTHER ANIMALS

  • Insects:
    • Use spiracles for air intake.
    • Have a tracheal system for gas exchange.
    • Oxygen diffuses from spiracles to cells, and carbon dioxide diffuses out.
  • Earthworms:
    • Exchange gases through their moist skin.
  • Frogs:
    • Possess lungs and can also respire through their skin.
  • Fish:
    • Utilize gills for aquatic respiration.
    • Gills facilitate gas exchange with dissolved oxygen.
  • Mammals, reptiles, and birds have lung-based respiratory systems.

Aquatic Respiration

  • Aquatic organisms have adaptations for extracting oxygen from water. Gills in fish are a prime example.
  • Gills:
    • Skin projections rich in blood vessels.
    • Enable gas exchange with dissolved oxygen.

Plant Respiration

  • Plants, like animals, require respiration for survival. They exchange gases with the atmosphere.
  • Plants take in oxygen and release carbon dioxide.
  • Leaves use stomata for gas exchange.
  • Roots obtain oxygen from soil air pockets.

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