what is meant by transportation?

In unicellular organisms, transportation of substances happens through diffusion and osmosis. Gases move in and out of the cell by diffusion. Other substances move by osmosis.

Diffusion: Random motion of particles in order to attain equilibrium of concentration is called diffusion. Diffusion can be observed in many aspects of day to day life. The aroma of food comes from the kitchen because of diffusion. A pleasant smell of flowers comes because of diffusion. Bad odour of garbage comes because of diffusion.

Osmosis: Movement of water through a semi-permeable membrane from high water concentration to low water concentration is called osmosis. Osmosis is a type of diffusion. Cell membrane is a semi-permeable membrane. Substances move across the cell membrane because of osmosis. Seeds swell up; when soaked in water; because of osmosis.