  We study the interplay of population growth and evolutionary dynamics using a
stochastic model based on birth and death events. In contrast to the common
assumption of an independent population size, evolution can be strongly
affected by population dynamics in general. Especially for fast reproducing
microbes which are subject to selection, both types of dynamics are often
closely intertwined. We illustrate this by considering different growth
scenarios. Depending on whether microbes die or stop to reproduce (dormancy),
qualitatively different behaviors emerge. For cooperating bacteria, a permanent
increase of costly cooperation can occur. Even if not permanent, cooperation
can still increase transiently due to demographic fluctuations. We validate our
analysis via stochastic simulations and analytic calculations. In particular,
we derive a condition for an increase in the level of cooperation.
