Alveoli or alveolar sac are present in lungs.They are also called as air sacs. The alveoli of lungs provide a large surface area for gaseous exchange. The number of alveoli in human lungs has been estimated to be approx. 300 million. The rich network of capillaries surrounding them help in exchange of gases. Both alveolar wall and capillary wall are made of squamous epithelium. It allows the exchange of gases according to their partial pressure differences.
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Organisms that are more complex, such as eukaryotes, have cells that are specialized for specific functions. Gene regulation needs to be more complex to produce these specialized cells for complex organisms. Please Mark Me Brainliest
