MCQ’s
Notes with Exercise
Class 11th Biology Chapter 13, Gaseous Exchange, discusses how organisms exchange gases with their environment, an essential process for cellular respiration and energy production. Here’s a general overview:
- Definition of Gaseous Exchange: Gaseous exchange refers to the process by which oxygen is taken in from the environment, and carbon dioxide, a waste product of cellular respiration, is released.
- Gaseous Exchange in Plants:
- Stomata: Small pores found on the surface of leaves. They open and close to allow gases (oxygen and carbon dioxide) to move in and out during photosynthesis and respiration.
- Lenticels: Openings in the bark of woody plants that facilitate gas exchange.
- During the day, plants take in carbon dioxide for photosynthesis and release oxygen. At night, they primarily respire, taking in oxygen and releasing carbon dioxide.
- Gaseous Exchange in Humans:
- Respiratory System: In humans, gaseous exchange occurs in the lungs, specifically in tiny air sacs called alveoli.
- Inhalation: Oxygen-rich air enters the lungs, where oxygen diffuses into the blood through the walls of the alveoli.
- Exhalation: Carbon dioxide, a waste product from cellular respiration, is carried from the blood to the alveoli and expelled from the body during exhalation.
- Mechanism of Breathing:
- Inspiration: The diaphragm and intercostal muscles contract, causing the chest cavity to expand and air to flow into the lungs.
- Expiration: The diaphragm relaxes, reducing the chest cavity’s volume and pushing air out of the lungs.
- Gaseous Exchange in Other Organisms:
- Fish: Use gills to extract oxygen from water and release carbon dioxide.
- Insects: Have a system of tubes called tracheae, which allow gases to diffuse directly to and from body tissues.
- Amphibians: Can exchange gases through their skin in addition to their lungs, especially in moist environments.
- Factors Affecting Gaseous Exchange:
- Surface area available for exchange (larger surface areas facilitate better gas exchange).
- Thinness of the respiratory surface (thinner surfaces allow for quicker diffusion of gases).
- Concentration gradient between the gases in the environment and in the body (a steep gradient allows for efficient gas exchange).
- Importance of Gaseous Exchange: It is crucial for maintaining the oxygen supply for cellular respiration, which produces energy (ATP), and for removing carbon dioxide, which can be toxic if it accumulates in the body.
This chapter explains the various methods and structures organisms use for the exchange of oxygen and carbon dioxide, highlighting its importance for survival and energy production.