observe vs check up on

observe and check up on both are verbs.

Word	Noun	Adjective	Verb	Adverb
observe	No	No	Yes	No
check up on	No	No	Yes	No

As verbs, check up on is a hypernym of observe; that is, check up on is a word with a broader meaning than observe:

Other hypernyms of observe include check, check into, check out, check over, go over, look into, suss out.

observe (verb)	check up on (verb)
stick to correctly or closely	examine so as to determine accuracy, quality, or condition
make mention of
watch attentively
observe with care or pay close attention to
discover or determine the existence, presence, or fact of by perception with the eyes
follow with the eyes or the mind
show respect towards
behave as expected during of holidays or rites
conform one's action or practice to