Of course. But while we can't draw an exact line where it begins, we can certainly categorize some obvious things as being on one side of it or the other.
In terms of thinking, feeling, and suffering, it's obvious that
1. pigs (for example) are certainly capable of these things, as least as much as a young human child, and
2. wheat is not meaningfully capable of these things.
So there is a moral cost to killing a pig that there isn't to killing a wheat plant.
This isn't something particularly revolutionary. It's illegal to torture and kill pigs outside of certain sanctioned contexts, so we recognize this intuitively as a society. We just choose to remain cognitively dissonant when it comes to our food sources.
This seems pretty intuitive. I think most people have roughly the same mindset.
You obviously need to participate in ending life to sustain yourself, but it's not necessary to end life capable of thinking, feeling, and suffering.