The correct answer is D.
The structure of human lungs is first demonstrated in an organism.
- Lungs are the respiratory organs. They are made up of alveoli.
Main Function :
- The main function of lungs is the gaseous exchange.
- This gaseous exchange occurs in the alveoli.
- Oxygen from atmosphere comes into the lungs through nostrils, nasal cavities, pharynx, larynx, trachea, bronchi and finally reaches the lungs.
- Then gaseous exchange occurs between blood and alveoli.
- Oxygen enters into the blood and carbon dioxide leaves the blood.
The structure of Earthworms Moist skin is second demonstrated in an organism.
- The earthworm has no special respiratory organs like lungs or gills.
- Respiration takes place through the body wall.
- The outer surface of the skin is richly supplied with blood capillaries which aid in the diffusion of gases.
- Oxygen diffuses through the skin into the blood while carbon dioxide from the blood diffuses out.
- The skin is kept moist by mucous and coelomic fluid and facilitates exchange of gases.
The structure of Fish Gills is third demonstrated in an organism.
- The gill filaments in fish have functions like lungs in people: it's the organ responsible for absorbing oxygen and expelling carbon dioxide.
- The gills also regulate levels of mineral ions and the pH of the blood, as well as being the primary site of nitrogenous waste excretion, in the form of ammonia.
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