I had assumed that 生物 was just a fancier word for 生き物 in the way that onyomi compounds often are. But when I looked in the dictionary I became less sure.
For 生物 I see:
Animals, plants, microbes etc. A generic term for things which are living.
But for 生き物 I get:
Living things. Especially animals. (synonym for) 生物
From these definitions I see that 生物 clearly refers to both plants and animals, but 生き物 seems to refer primarily to animals. But then the definition of 生き物 says it is a synonym for 生物.
So the question is, are these words synonyms or do they have distinct meanings? Would it be weird to refer to plants as 生き物 for example?