When should students collaborate during inquiry learning using an online learning environment? We compare "continuous collaboration" to "individual predictions" followed by collaborative exploration of natural selection and evolution in a unit featuring interactive models illustrating the marine biodiversity crisis. In the individual condition students made their own predictions about the dynamics of a simulated fish population subject to predation before comparing and discussing their ideas in pairs. In the continuous condition students collaboratively predicted and discussed their ideas. Results suggest that the individual condition where students developed and expressed their own ideas before sharing them with a peer enabled them to refine their thinking and improve their understanding of natural selection better than the continuous condition.