Most range models relate current species' localities to underlying environmental conditions. These correlative range models largely ignore biological traits including size, physiology, and behavior. My research focuses on incorporating these biotic details into mechanistic models that link individual energetics and population dynamics to predict climate-induced range shifts for reptiles and amphibians. My NCEAS research applied the models to demonstrate how differential traits among lizard species lead to differential responses to climate change. Additional research demonstrated the range implications of geographic variation in physiology among lizard populations. Ongoing research is investigating how trait adaptation across latitudinal gradients determines ranges. These findings show that biology matters when predicting responses to climate change. In a quantitative comparison of correlative and mechanistic range models, we found that both classes of models can be useful depending on particular model assumptions and the quality of existing data needed to parameterize models. Mechanistic range models are emerging as a viable alternative to correlative approaches and may be essential to predicting range dynamics in changing environments.