This is the first of five chapters on ecological modelling and presents basic homogenous (absence of spatial structure and variability among individuals) and deterministic (absence of stochasticity and randomness) population models. The first model describes unlimited exponential growth, which is followed by the introduction of intra-specific competition and density dependent growth. Two types of dynamics are considered: continuous in time and discrete in time. It is demonstrated that the time-discrete formulation can lead to chaotic population dynamics which in ecological models can be caused by scramble competiton where individuals share limited resources rather evenly so that all individuals suffer from the lack of resources. Opposed to this is contest competition where the share of the resources is uneven, so a few winners reproduce and/or survive, and the emerging population dynamics are not chaotic.