Transport is the movement of materials to-and-fro from the cells.
In unicellular organisms, which are single celled, the cell can directly absorb the food, water and air from the surrounding. Plants and animals are multi-cellular organisms. They are made of large collection of cells. These cells need water, minerals and nutrients for their growth and survival. The cells are not in direct contact with their surroundings, thus cannot directly exchange the nutrients with the surrounding. The multi-cellular organisms however have a special network of tubes and vessels that make the supply of nutrients to the cells within the body possible.
