2.52: Understand the Need for a Transport System in Multicellular Organisms

TRANSPORT SYSTEM: A system that provides a constant supply of necessary substances through a medium to cells via an exchange surface - e.g circulatory system

MULTICELLULAR ORGANISMS: Organisms composed of more than one cell

MULTICELLULAR ORGANISMS RELY ON DIFFUSION

Diagram showing the Relation between Surface Area and Volume

EXPLANATION: As Multicellular organisms are composed of more than one cell, they have a small surface area in relation to their volume, and hence have a small surface area to volume ratio With a small surface area to volume ratio, Multicellular organisms therefore have inefficient rate of diffusion, preventing cell to rely on diffusion to transport necessary substances in and out of the cell (rate of metabolism will exceed rate of exchange of vital materials and wastes) Hence, Multicellular organisms rely on transport systems to provide a constant supply of necessary substances through a medium to their cells via an exchange surface

COMMON FEATURES OF TRANSPORT SYSTEMS: TUBES OR VESSELS Tubes or vessels to carry necessary substances from one part of organism to another in a structured process     2. CLOSE CONTACT WITH CELLS Transport system will have close contact with cells via exchange surface for efficient exchange of necessary substances     3. PUMPS Transport system may have pumps to ensure a constant supply of necessary substances to cells - the heart acts as a pump to ensure the constant circulation of blood by which materials are transported by in the human circulatory system