This thesis focuses on the discussion of ecological models. Ecological models try to picture how different species interact with one another. While there are many ways two species can interact with each other, in this thesis we focus on three main interaction models. The first model is the Lotka-Volterra predator-prey-model, where one species is prey to the other. Then, a competition model is introduced, in which both species live of the same resource. Lastly, a model of a symbiotical interaction between two species is discussed, where both species benefit from one another. Starting with strongly simplified models, we then progress to expand them to better reflect natural occurrences. Finally some practical uses of these ecological models are presented, to show which significance they hold in different fields.