    ‘Sentence i: Why, are the’ left-Gnd ‘right sides ofthe  human heart divided into’ ventricles grid trig?    Sentence & The function’ of ‘the .‘attia,*is__rigrely  pumpin. blood recigved ‘from the'‘veria “cawrd dd  pulmp siéin to the .ventriciés. Why oouldin” we :have-  evolved a: heart. with’ no atid ard the. Sipoatrial Node  being on- "the ventricles, -which. “Would’ ‘increase  ventricilar coriractién and decrease ‘energy ‘required  for. heartbeat?