NCERT Gist: Respiration in Organisms | Additional Study Material for UPSC PDF Download

- The process of breakdown of food in the cell with the release of energy is called cellular respiration.
- Cellular respiration takes place in the cells of all organisms.
- In the cell, the food (glucose) is broken down into carbon dioxide and water using oxygen.
- When breakdown of glucose occurs with the use of oxygen it is called aerobic respiration.
- Food can also be broken down, without using oxygen. This is called anaerobic respiration.
- Breakdown of food releases energy.
- There are some organisms such as yeast that can survive in the absence of air. They are called anaerobes.
- They get energy through anaerobic respiration
- In the absence of oxygen, glucose breaks down into alcohol and carbon dioxide.
- Yeasts are single-celled organisms.
- They respire anaerobically and during this process yield alcohol. They are, therefore, used to make wine and beer.
- Our muscle cells can also respire anaerobically, but only for a short time, when there is a temporary deficiency of oxygen.
- 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.
- When we inhale air, 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.
- Breathing involves the movement of the diaphragm and the rib cage. A cockroach has small openings on the sides of its body. Other insects also have similar openings. These openings are called spiracles.
- Insects have a network of air tubes called tracheae for gas exchange.
- Oxygen rich air rushes through spiracles into the tracheal tubes, diffuses into the body tissue, and reaches every cell of the body.
- Earthworms breathe through their skins.
- The skin of an earthworm feels moist and slimy on touching. Gases can easily pass through them.
- Though frogs have a pair of lungs like human beings, they can also breathe through their skin, which is moist and slippery.
- Gills in fish help them to use oxygen dissolved in water.
- Gills are projections of the skin.
- Gills are well supplied with blood vessels for exchange of gases.