"In this book, authors would like to investigate the application of discrete fractional operators to biological, chemical reaction and chaotic system with applications in physics. The dynamical analysis will be carried out using the equilibrium points of the system for studying their stability properties and chaotic behavior will be illustrated with the help of bifurcation diagrams and Lyapunov exponents. The book is divided into three parts. Part - I is dedicated for the analysis of biological systems like tumor immune system and neuronal models with introducing memristor based flux control. There are very few works carried out with flux controlled memristor elements in biological systems, we in this book would like to provide new direction towards the study. The memductance functions are considered as quadratic, periodic, exponential functions. Part - II of the books depicts the application of discrete fractional operators in chemical reaction-based systems with biological significance. Here, we perform analysis of two different chemical reaction models one being disproportionation of glucose, which plays important role in human physiology and other constitutes the Lengyel - Epstein chemical model. Chaotic behavior of the systems is studied and the synchronization of the system is performed in this part of the book. For the final part of the book, we propose the complex form of the Rabinovich-Fabrikant system which describes physical systems with strong nonlinearity exhibiting unusual behavior. This chapter will provide the study of the Rabinovich- Fabrikant system using discrete fractional operator. The chaotification technique and the application of the systems will be explored in the final chapter. The book as a whole will provide a detailed understanding of the importance of constructing models with discrete fractional operators and change in dynamics between commensurate and incommensurate order systems"--