fauna vs organism

fauna and organism both are nouns.

Word	Noun	Adjective	Verb	Adverb
fauna	Yes	No	No	No
organism	Yes	No	No	No

As nouns, organism is a hypernym of fauna; that is, organism is a word with a broader meaning than fauna:

fauna: a living organism characterized by voluntary movement
organism: a living thing that has (or can develop) the ability to act or function independently

Other hypernyms of fauna include being.

fauna (noun)	organism (noun)
a living organism characterized by voluntary movement	a living thing that has (or can develop) the ability to act or function independently
all the animal life in a particular region or period	a system considered analogous in structure or function to a living body