Transport systems in multicellular animals


Why are transport systems needed in multicellular animals?

1. Diffusion alone is not sufficient to meet the metablic demands of the animals.                           2. Hormones are made in one area but need to be transported to another                                     3. Small SA:V meaning that diffusion is not sufficient to absorb or remove materials                             4. Food is digested in one organ but needs to be transported to individual cells for respiration     5. Metablic waste needs to be transported to excretory organs

Types of Ciculatory systems:

When substances are transported in a mass of fluid with a pumping system: Mass transport system

Open circulatory system: very few vessels, blood pumped out of the heart to the open body cavity and come sinto direct contact with tissues at a low pressure, blood returns to the heart through open ended vessel.

Example: insects contain open circulatory system. Heart extends along the thorax. The blood does not contain oxygen or


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