Animals can live only on what plants have already turned fro

what =something that,具体分析如下：
1 Animals live on something.2 plants have turned THE something from inorganic to vegetable matter.现在把这两句合并起来：Animals live on (something that=)what plants have turned (something 这个字在这里不能再写了,已经被前面what取代了) from inorganic to vegetable matter.这是定语从句.
2 如果把what放入以上这段话,它应该是在什么位置呢?
plants have already turned WHATfrom inorganic to vegetable matter (在turned的后面).
--------------------(我相信,你已经明白了.wish you a good day.)---------------
再问： 非常详细，感谢，其实我已经明白你的意思了，但还想确认一下我理解的没错：what前面的（something that）这个词组是被省略掉了吗？还是只是等同于what？ 能不能详细翻译一下这个句子呢Animals can live only on what plants have already turned from inorganic to vegetable matter.
再答： 动物只能食用植物从无机物到蔬物质转变过来的有机物质。