Explain the cause of circulatory in frog

In the frog, Rana, venous blood is driven into the right atrium of the heart by contraction of the sinus venosus, and it flows into the left atrium from the lungs. A wave of contraction then spreads over the whole atrium and drives blood into the ventricle, where blood from the two sources tends to remain separate.

Explanation:

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the sphincter muscles at the end of the digestive tract is the anus.

frogs. the lower the ph the higher the acid content. frogs have the highest tolerance in this scenario.