In the sentient levels, the goal is to prevail over active motes of various types that hunt and absorb other motes, including the player. Hunting them typically involves absorbing as many inactive motes as possible before chasing down the active ones with the extra mass one has gained.
S1O - artificial life
S1O1 - Absorb the Ovarium
The Ovarium is the first cell that you will encounter. It will attempt to move towards other cells, but will also try evading any attackers. It only shoots motes at a slow rate.
On the normal map, try moving downward to collect the blue motes. When you are large enough, which shouldn't take too long, return to the ovarium and try to claim it.
S1O2 - Absorb the Biophobe
The biophobe won't attack other motes, but if a larger mote gets too close, it will rapidly fire motes in an attempt to escape.
S2O - survival of the fittest
S2O1
S2O2
S2O3
S3O - deadly ecosystems
S3O1
S3O2
S3O3
One way to beat this difficult level is to randomize the map enough times such that you spawn right next to the Forax, which can allow you to quickly intercept it before it can gain enough mass to absorb you. With the right spawn placement, it is possible to beat this level in under 2 seconds.