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## Let Us Revise Mark the following statements [T] if true and [F] if false. 1. The air breathed in, passes from nostrils through the trachea to the pharynx. 2. Alveoli are the units of lungs. 3. In the cell, energy is obtained by breaking down sugars into carbon dioxide and water in the presence...

## Let Us Revise Mark the following statements [T] if true and [F] if false. 1. The air breathed in, passes from nostrils through the trachea to the pharynx. 2. Alveoli are the units of lungs. 3. In the cell, energy is obtained by breaking down sugars into carbon dioxide and water in the presence of oxygen 4. When we inhale air, ribs move down and inwards while the diaphragm moves up. 5. The rib cage is an essential part of the respiratory system. ## Activity 10.2 ### Materials needed: * A breaker, a glass tube bent at right angles at two places * A cork with a hole, thread and coloured water * A small test tube, Potassium hydroxide solution or KOH solution * Vaseline and germinating gram seeds ### Method: * Put some germinating gram seeds in a conical flask. * Insert the short end of the glass tube through the hole in the cork. * Before fixing the cork on the flask suspend a tube containing KOH solution using a thread in the flask. * Take some coloured water in a beaker and dip the longer side of the glass tube inside it. * Apply Vaseline on the rim of conical flask to prevent air from entering * Note down the initial level of water in the tube. * Keep the set up for two hours and not down the final level of water without disturbing it. ### Observation: Water level rises in the bent glass tube. ### Conclusion: Carbon dioxide released by the seeds is absorbed by the KOH solution. This creates a partial vacuum in the flask forcing the water to rise up in the bent tube. The rise in level of water indicates that seeds release carbon dioxide during respiration.