ABSTRACT This study investigates the role of visual perception in data-based scientific reasoning within population dynamics. Visual perception involves representational characteristics of stimuli and context-based conceptions, influenced by top-down (contextual assumptions) and bottom-up (data representation) effects. In population dynamics, top-down effects relate to assumptions like natural equilibrium, while bottom-up effects concern how data are represented, typically through line graphs. We assessed pre-service biology teachers’ (N = 20) initial conceptions on population dynamics, categorizing them as either the Balance of Nature (BoN) or Flux of Nature (FoN) metaphors. Participants viewed line graphs depicting population dynamics while eye-tracking technology recorded their visual focus and think-aloud protocols provided verbal data. ANOVA results showed significant differences in eye-tracking metrics between AOI groups of BoN and FoN graphs, but no significant effects between initial conceptions and eye-tracking measures. Heat map analyses revealed that participants focused on visually prominent graph features, especially when interpretation required conceptual knowledge and pattern identification.