Answer to Question #281358 in Zoology for Applied Biology

Question

why animals evolved lung to live on land, why not animals with gills?

Answer 1

Gills are evaginations of the body surface. Some open directly to the environment; others, as in fishes, are enclosed in a cavity. In contrast, lungs represent invaginations of the body surface. Many invertebrates use gills as a major means of gas exchange; a few, such as the pulmonate land snail, use lungs. Almost any thin-walled extension of the body surface that comes in contact with the environmental medium and across which gas exchange occurs can be viewed as a gill. Gills usually have a large surface area in relation to their mass; pumping devices are often employed to renew the external medium.