We discussed the different models that might appear on 2020 Ap exam. Those models will be only from units one to five. We talked about the different stages in the demographic transition and how the natural increase rate changes. We also talked about the kind of diseases that might occur in those stages through discussing the Epidemiological transition model. We also talked about the migration patterns that occur in those stages through studying zelinsky model of migration. We reviewed ravenstein's laws of migration and we talked about the characteristics of migrants.