I'd like to explore some details on a so-called water-ball planet (i.e. a planet in the habitable zone of a sun, covered by a 100 km deep ocean). I am particularly interested where life could develop on such a planet.
In the previous question What are the conditions of an Earth-like, water-ball planet? I asked about the composition of the ocean and it turned out that it will be probably depleted of phosphate, an essential element for earthly life forms.
Given the current theories of how life developed on Earth, which theories would also apply to a water-ball planet? If life could have developed using the same mechanisms as it did on Earth (not necessarily using the same chemical compounds), at what point would further Earth-like evolution be impossible due to the conditions on the water-ball planet?