The order certainly didn't come from some ridiculous anthropomorphized deity because then what would have made the deity? It is entirely possible for nature to produce its own "laws" and it is entirely possible for nature to break them as well, which is likely how this universe came to be. I do not have a degree in physics and thus cannot explain it well enough for you to be satisfied with the answer (though who could explain it well enough for you to be satisfied?). As humans we cannot even fathom how the order of existence works, we try to find out with physics but our minds are very limited, which is one reason why our species invented deities and religion, to explain what could not at the time be explained by science. We have come far enough in science to debunk the existence of deities. If one wants to take a pantheistic view, that would make more sense than all the other ridiculous religious views floating around. In pantheism, the universe itself is god, not some silly deity with human or animal qualities and personalities. The "laws" of physics are simply what we have observed, they are not laws like what a congress passes with bills.
In the order of existence, yes lettuce has the same value as i do or may even have a greater value depending on what comes to eat, live off of, or enjoy it. All things have some form of value, be they plant or animal or even rock. Just because man is too stupid to see the value doesn't mean it is non-existent. The average joe schmoe sees a piece of lettuce as nothing more than salad, an advanced mind sees sustenance, which gives it value, the plant itself valued its existence once, though, once again, we humans may not understand by what mechanism a plant could understand its value. But the plant does value itself or it would not work so hard to survive. An insect sees it as sustenance, which gives it value. The rocks have value because they make up the landscape, build up the planet. If it exists, it has some form of value. Asbestos even has value. Every atom, every electron can be valuable. That said, just because things have obvious value in the grand order of existence does not mean some magical sky creature is making that order exist. Someday, perhaps while man still exists (though probably not), the laws of physics could change, violently and our universe could disappear or give rise to a new one. Please do direct any further questions to a physicist.