Briefly explain why it’s important to know how cells function

Knowing the biochemical processes in a cell is significant in medicine and other fields such as agriculture. In medicine,  this knowledge can inform the development of pharmaceuticals that treat diseases that affect cells. In agriculture, this knowledge can be used in the fight against plant diseases hence improving yields.  

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

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.