please answer this if you can by today.I have an exam tomorrow

Asked by  | 21st Dec, 2008, 09:54: AM

Expert Answer:

In single-celled organisms, the entire surface of the organism is in contact with the environment for the diffusion of substances.


In multi-cellular organisms all cells may not be in direct contact with the surrounding environment. So simple diffusion will not meet requirements of all the cells. So in multi cellular organisms, a specialised transport system is required to transport oxygen to cells deep within the body.



Answered by  | 21st Dec, 2008, 10:11: PM

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