"C" Climate change, because if the past time had more hurricanes than in these times, then the weather has changed. .
A double circulatory system is composed of a <u>PULMONARY </u>circuit and a(n) <u>SYSTEMIC </u>circuit
Pulmonary circulation means where blood goes to lungs to get purified and exchange gases, i.e. CO2 is released into the lungs and oxygen is taken into the blood.
Systemic circulation is between heart and entire body, where oxygen is supplied to every cell of the body and CO2 is absorbed.
Before the Siderian period the world had much less oxygen in it. Meaning, seas devoid of oxygen. Durring the Siderian the algae activity that signifies the period began to pump oxygen into the oceans. Allowing then unreactive metalic iron in the sea to be precipitated out into iron oxide. In the case of temperature being a culprit in the Siderian, most likely not. Unless you factor it into giving the agal life energy. Temperature does affect oxidation, but oxidation cannot occur without oxygen. The higher the temperature, the easier it is for oxygen to bond with iron, the lower, the slower it will react.
