Question

why multicellular organism required special organs for exchange of gases between their bodies and their environment?

please answer fastly

Answer 1

In multicellular organisms ,all cells may not be in direct contact with the surrounding environment. so, multicellular organisms required special organs for exchange of gases between their bodies and their environment.

Answer 2

In unicellular organisms gaseous exchange takes place by the process of diffusion. Since the cells are in direct contact with environment. Therefore oxygen requirement is fulfilled by diffusion.

But in case of multicellular organisms, diffusion is insufficient to fulfill the oxygen requirement because :-
1. All body cells are not in direct contact with environment.
2. Diffusion is a slow process. It will take too much time to supply oxygen to all the cells.