Structure of ‘staying together’ life cycles for a population with the maximal group size n = 3. (a) Schematic figure for the life cycles of a population with n = 3. Birth rates bi are identical for all cells in the same group size i. Fragmentation probability set q = (q1+1; q2+1, q1+1+1; q3+1, q2+2, q2+1+1, q1+1+1+1) determines the life cycle of the group structure. (b) Pure life cycles are obtained in a special case where a single fragmentation probability is equal to one, while all others are zero. An example of a pure life cycle using the fragmentation mode q = (0; 0, 0; 0, 0, 1, 0) is presented. In a pure life cycle, all groups follow a regular schedule of development and fragmentation. (Online version in colour.)