We have our musical ecosystem running; living, breeding, feeding and dying. I haven't set a finish line on this project, the main purpose is to give you ideas, and you're free to set your own objectives with it.
Perhaps you're interested in coding behaviours and want to add additional organisms, maybe a predator, or something less usual like a benevolent parasite. Maybe you're more interested in sound and want to explore the potential of Web Audio and get to know the library Tone.js. Perhaps you'd like to focus on visuals and explore drawing & animating in Canvas further. Or maybe you could look at interaction, taking these ideas in the direction of making a video game.