  In this work, we outline a mathematical description of biodiversity evolution
throughout the Phanerozoic based on a simple coupled system of two differential
equations and on the division of genera in two classes - Short-lived and
Long-lived types, as used by Rohde and Muller. We show that while the division
in only two classes cannot capture the complexity of biodiversity evolution in
short scales, broad trends can be described well. We also compute the systems'
Green functions as a way to qualitatively describe the possible effects of
intense perturbations of astrophyisical origin on the subsequent biodiversity
evolution.
