Abstract Despite being an essential micronutrient, copper is also a potentially toxic heavy metal. Using selection experiments, we produced Chlamydomonas reinhardtii populations with increased tolerance of copper ions and then derived pure cell lines from these populations. Strains derived from the same population (both adapted and nonadapted) significantly differed in terms of growth parameters. Cultivation of the strains in a range of copper ion concentrations revealed differences in growth and photosynthetic performance, which could be attributed to microevolutionary processes occurring with each cell division. Our results demonstrate the effects of environmental factors on rapidly multiplying microorganisms.