Mammals and birds have four-chambered hearts and fully divided pulmonary and systemic circulations. the circulatory systems of reptiles and amphibians are sometimes presented as “inferior” because pulmonary and systemic circulations are not completely separate. what might be an advantage to incompletely separated circuits in these organisms?

According to the rna world hypothesis, rna acted as the genetic material and catalyzed reactions in ancient cells. what conclusion can you draw from this?               a.  this implies that dna and proteins aren't essential in cells today.    b.  this implies that rna can catalyze any chemical reaction that enzymes catalyze.    c.  this implies that if a cell has a problem with its dna, its rna can compensate for the damaged dna.    d.  this implies that dna and proteins evolved after rna.