Topic outline

    • Respiration in Organisms

      Q20. What is inhalation and exhalation?

      Ans. 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.


      Q21. How do frogs breathe?

      Ans. Frogs have a pair of lungs like human beings to breathe air. They can also breathe through their skin, which is moist and slippery.


      Q22. Name some animals that breathe through lungs.

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


      Q23. Why do mountaineers carry oxygen with them?

      Ans. Mountaineers carry oxygen with them because the amount of air available to a person is less than that available on the ground.

      Q24. Why should we cover our nose while sneezing?

      Ans. When we sneeze, we should cover our nose so that the foreign particles we expel are not inhaled by other persons.


      Q25. How does respiration occur in earthworms?

      Ans. Earthworms breathe through their skins. The skin of an earthworm feels moist and slimy on touching. Gases can easily pass through them.


      Q26. What role does hair present in the nasal cavity play in the process of respiration?

      Ans. When we inhale, the particles get trapped in the hair present in our nasal cavity. Thus, the hairs present in the nasal cavity filters the air.


      Q27. What is normal range of breathing rate per minute in an average adult person at rest?

      Ans. On an average, an adult human being at rest breathes in and out 15ñ18 times in a minute.


      Q28. Why do we get muscle cramps after heavy exercise?

      Ans. The cramps occur when muscle cells respire anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps.

      Q29. What happens during exhalation?

      Ans. 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.


      Q30. What happens during inhalation?

      Ans. 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.


      Q31. What happens to the air we breathe in?

      Ans. The air we breathe in is transported to all parts of the body and ultimately to each cell. In the cells, oxygen in the air helps in the breakdown of food and energy is released.


      Q32. How does respiration work in yeast?

      Ans. Yeasts are single-celled organisms. They get energy through anaerobic respiration. In the absence of oxygen, glucose breaks down into alcohol and carbon dioxide.


      Q33. Why are yeasts used to make wine and beer?

      Ans. Yeasts are single-celled organisms. They respire anaerobically and during this process yield alcohol. They are, therefore, used to make wine and beer.

      Q34. What is the function of gills in fish?

      Ans. Gills in fish help them to use oxygen dissolved in water. Gills are projections of the skin and are well supplied with blood vessels for exchange of gases.


      Q35. How do plant roots respire?

      Ans. Like all other living cells of the plants, the root cells also need oxygen to generate energy. Roots take up air from the air spaces present between the soils particles.


    • Download to practice offline.