Respiration in Organisms notes for science class 7 NCERT, PSTET and CTET

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Our Each cell of an organism performs certain functions such as nutrition, transport, excretion and reproduction.

To perform these functions, the cell needs energy.

 

From where the cell get energy?

The food has stored energy.

This stored energy gets released during respiration.

All living organisms respire to get energy from food. Breathing is a part of respiration. During breathing, we breathe in air and air contains oxygen. We breathe out air which is rich in carbon dioxide. The air we breathe in is transported to all parts of the body and ultimately to each cell.

Oxygen in the air helps in the breakdown of food.

The process of breakdown of food in the cell with the release of energy is called cellular respiration.

Types of Respiration

Food can also be broken down, without using oxygen.

So energy can be released from cells in the presence OR absence of oxygen.

When breakdown of glucose occurs with the use of oxygen it is called aerobic respiration.

Examples: In most of our body cells Aerobic respiration takes place.

Food can also be broken down, without using oxygen. This is called anaerobic respiration.

Examples: Some organisms like Yeast thrive/Lives in oxygen deficient conditions. They are called anaerobes. Muscles cells can also respire anaerobically



Why you get muscle cramps after exercise?

  • The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps.
  • The cramps get normal on warm water bath or massage because that increase blood circulation helps in complete breakdown of lactic acid into carbon dioxide and water.

BREATHING

  • Breathing means taking in air rich in oxygen and giving out air rich in carbon dioxide with the help of respiratory organs.

    The taking in of air rich in oxygen into the body is called inhalation and giving out of air rich in carbon dioxide is known as exhalation.

    It is a continuous process.

    The number of times a person breathes in a minute is termed as the breathing rate.

    During breathing inhalation and exhalation take place alternately.

    A breath means one inhalation plus one exhalation.

    Mechanism of breathing.

    Air enters through our nostrils.

    It passes through our nostrils into the nasal cavity.

    From the nasal cavity, the air reaches our lungs through the windpipe.

    Lungs are present in the chest cavity.

    This cavity is surrounded by ribs on the sides.

    A large, muscular sheet called diaphragm forms the floor of the chest cavity

Inhalation and Exhalation

    • INHALATION: During inhalation, ribs move up and outwards and diaphragm moves down. This movement increases space in our chest cavity and air rushes into the lungs. The lungs get filled with air.
    • EXHALATION: During exhalation, ribs move down and inwards, while diaphragm moves up to its former position. This reduces the size of the chest cavity and air is pushed out of the lungs.

    Why do we Sneeze?

    Our Nasal cavity has hairs in it, these hairs trap the dirt particles in air, sometimes these particles may get past the hair in the nasal cavity. Then they irritate the lining of the cavity, as a result of which we sneeze. Sneezing expels these foreign particles from the inhaled air and a dust free, clean air enters our body.

REATHING IN OTHER ANIMALS

Animals such as elephants, lions, cows, goats, frogs, lizards, snakes, birds, have lungs in their chest cavities like the human beings.

Insects respire using Tracheal system:-

A network of tubes interconnected with each other, this network is called as tracheae, the ends of tubes have openings for gaseous exchange, these openings are called spiracles.

Earthworm and Frogs respire through skin

The skin of earthworm and frog feels moist and slimy on touching. Gases can easily pass through them. Although frogs have lungs, but they do respire through skin.

Breathing under Water in Fishes

Gills are projections of the skin. Gills are well supplied with blood vessels for exchange of gases.

Respiration In Plants:

The leaves of the plants have tiny pores called stomata for exchange of oxygen and carbon dioxide. The root cells also need oxygen to generate energy. Roots take up air from the air spaces present between the soil particles.

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