germ vs complex body part

germ and complex body part both are nouns.

Word	Noun	Adjective	Verb	Adverb
germ	Yes	No	No	No
complex body part	Yes	No	No	No

As nouns, complex body part is a hypernym of germ; that is, complex body part is a word with a broader meaning than germ:

germ: a small apparently simple structure (as a fertilized egg) from which new tissue can develop into a complete organism
complex body part: a particular complex anatomical part of a living thing and its construction and arrangement

Other hypernyms of germ include anatomical structure, bodily structure, body structure, structure.

germ (noun)	complex body part (noun)
a minute life form (especially a disease-causing bacterium); the term is not in technical use	a particular complex anatomical part of a living thing and its construction and arrangement
a small apparently simple structure (as a fertilized egg) from which new tissue can develop into a complete organism
anything that provides inspiration for later work