Question

how does blood get supplied to the cells of animals who do not have arteries ?

Answer 1

Transport system in simple organisms

In unicellular organisms like Amoeba food and gases are directly taken from the surroundings and wastes are thrown out through the cell membrane. The movement of food and gases inside the cell takes place by the movement of cytoplasm.

In simple multicellular organisms like Hydra, the transportation of material from cell to cell takes place through simple diffusion.