The transport system is necessary in a plant or in an animal because of the following reasons:

1) In plants, water and dissolved minerals are transported from roots to leaves by xylem whereas prepared food is transported from leaves to all parts of the plant by phloem. Thus, xylem and phloem transport substances in plants.

2) If there were no transport system in plant, leaves would not get water for the photosynthesis and thus, they would not be able to make food and all the parts of the plant would not be survived without food and hence, plant would die.

3) In case of animals, food and water are transported to all parts of the body so that they can generate energy and grow. Similarly, waste products produced during the function of body cells are transported to their respective organs so that they can be excreted.

4) If there were no transported system in animals, they would not be able to get energy and get rid of waste. Thus, their survival would not be possible.