Are there really that many other ways? Photosynthesis, sure, but that doesn't seem to produce much and doesnt allow much "liveliness".
Anyway...
The 'why' is trivial-seeming to me. Once one organism can consume ready-made nutrients from another organism for less energy cost than producing, it will, or it will be out competed by others who do. So carnivores exist everywhere. Even deer happily eat baby birds that they come across, and rabbits eat their own.
Anyway... The 'why' is trivial-seeming to me. Once one organism can consume ready-made nutrients from another organism for less energy cost than producing, it will, or it will be out competed by others who do. So carnivores exist everywhere. Even deer happily eat baby birds that they come across, and rabbits eat their own.
Almost Tragedy of the Commons?