Explain the Scaling from individuals to Ecosystems?

Models that explain how individual organisms acquire energy and materials, and how they use them for survival, growth and reproduction, have the potential to link ecological processes at several levels (Kooijman 2000). Dynamic physiological models that explain the flows of energy and elemental matter through individuals, and models that ascertain how these flows scale-up to higher organizational levels, have so many different applications. These models can contribute to life history theory, offer strong constraints on the dynamics of populations, and make the foundation for analytically and computationally tractable models of ecosystems.