This MATLAB code simulates the solution to Fisher's equation, which models the spread of an advantageous gene in a population, using a finite difference method and the Runge-Kutta 4th order scheme. The code initializes parameters like the spatial and temporal grids, sets up the tridiagonal matrix A for the spatial derivatives, applies boundary conditions, initializes the population distribution function, iteratively solves the PDE at each time step by calculating the RK4 coefficients, stores the solution in a matrix, and plots the results in a video.