Question

Unicellular organisms have no specific organ for various requirements

Answer 1

unicellular organism don't require any organ because their entire body is in contact with environment. All these stuffs occurs by diffusion so there's no need for specific organ.

Answer 2

Answer:

Because the entire surface of the organism is in contact with the environment, single-celled organisms do not require specific organs for taking in food, exchanging gases, or removing waste. 

Thus, simple diffusion is sufficient for gas exchange, and no specific organs are required.