Question

As Covid-19 is so tragically showing us proper lung function is crucial for survival. At the same time many organisms (e.g. Annelida, Platyhelminthes) do not have specialized respiratory organs at all. Explain how these organisms survive without respiratory organs and why we cannot do the same thing.

Answer 1

Question

The platyhelmenthis respire by absorbing oxygen directly through the skin into the body cell. Similarly most of the annelids too respire with the help of their skin by diffusion. These are very small invertebrates animals. Therefore the skin of these animals serve the role of lungs. As these are very small animals and do not much energy or much oxygen they can survive without lungs but mammals are big animals, they are mostly terrestrial and need oxygen in high amount as well as expel carbon dioxide in order to meet their energy demand, which can only be performed by well developed lungs.