In unrelated news, I find myself wondering about predator-prey relationships. Clearly this is a specialization which has occurred over and over again on an evolutionary time scale. Otherwise all predators would be of one line of descent, and all prey of another. Yet aviforms, mammals, fish -- every phylum, every class has this split. What would a biosphere be like where the predator-prey split happens much earlier, and is an unbridgeable gap? Or is this what plants are, to animals?
ETA: This predator-prey thing came from me looking at the wallpaper in the bathroom here at the coffeehouse, which shows a trout striking at an insect. Never a moment wasted in my world!