What single cell flourished on earth

Prokaryotic single-celled organisms.

Explanation:

even though many debate on this. the earliest forms of like pretty much began with bacteria. During the Precambrian Timespan most life was composed of these single celled organisms.

endo:

regulates body hormones, aldosterone, vasopressin

neural:

signal, regulates body using electric signals, reflex

endo has to do with hormones; aldosterone and vasopressin are both hormones. i also had this question and got it right : d

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