- Animals that have double circulation systems need blood to be supplied to their tissues quickly due to their relatively high metabolic rates i.e. rates of energy used in the chemical reactions within their bodies (compared with e.g. fish). This necessitates sufficient blood flow because the transport functions of bloodinclude supplying the tissues with the chemical substances needed to continue activities including the essential chemical reactions.
- Animals that have double circulation systems also need to maintain relatively high body temperatures - which requires sufficient blood flow due to the blood's role in maintaining body temperature as neOcessary for homeostasis.
Source: http://m.ivyroses.com/Biology/Transport/Double-Circulation.php
