Investigation of How Temperature Impacts the Population Growth Rate of Tetrahymena thermophila

  • Saurav Acharya
  • Jocelyn Cheng
  • Maddy Haines
  • Sung Ju Lee


Global temperatures are increasing as a result of climate change (Hansen et al., 2010). Alterations in temperature have the potential to significantly impact all ecosystems and the species that inhabit them. Tetrahymena thermophila (T. thermophila), a freshwater phagocytic cilate, is one of many species that may be impacted by rising water temperatures. The objective of this study was to measure the differences in the population growth rate of wild-type T. thermophila at 11°C, 20°C, 30°C, and 40°C, respectively. This experiment was executed by initially diluting the stock solution of T. thermophila with Tetrahymena media, SSP growth medium. This step was performed to provide optimal conditions and avoided restricting growth rates of T. thermophila by limiting space and nutrients. A sample was taken to be counted at each respective temperature every 2 hours for a total of 8 hours and lastly, at the 26 hour mark to complete the growth curve. A one-way ANOVA analysis was performed and a p-value of 0.04706 was obtained. This provided moderate evidence to reject the null hypothesis at a 5% significance level that temperature has no effect on T. thermophila population growth rate. The rejection of the null hypothesis lent support for the alternative hypothesis that temperature does in fact have an effect on population growth rate. Overall, it was noted that as temperature increases, growth rate increases as well. Using a post-hoc Tukey-Kramer HSD test on the oneway ANOVA results, it was determined that there was a significant difference in the population growth rate for the 11°C and 40°C treatment groups.