Well there are infact 2 walls. There is the atrial septum which separates right and left atriums. And there is the ventricular septum which separates the right and left ventricles.
I'm not quite sure if if it's asking you for two or one answer, but maybe writing both shall help.
They are found in any habitat but most live on lan, mainly in soil or on plant material
Oxygen, nitrogen, carbon, hydrogen NOT magnesium
