Evolution on similar time scales to those of population dynamics has been recognized for decades. Selection mediated by ecological interactions can change heritable phenotypic variation and lead to evolutionary dynamics, and that, in turn, affects ecological interaction. Hence, understanding of population dynamics should be insufficient without taking account of the feedbacks between ecological interaction and trait evolution. In this study, we examined the feedbacks between ecological and evolutionary dynamics using a predator-prey (rotifer-algal) system cultured in laboratory. We used some pairs of algal clones that have different fitness tradeoff and observed both population dynamics and changes in algal clonal frequencies (evolutionary dynamics) at the same time. Depending on the algal pair used, various patterns of population and evolutionary dynamics occurred, although the feedbacks between ecology and evolution was too complicated to understand intuitively. We would like to discuss the underlying mechanisms of the observed eco-evolutionary dynamics based on the ongoing theoretical analysis.