Organization and variation as theoretical principles for biology

We argue that a theory of biological systems should rely on organization and variation as theoretical principles. As such, these principles are fundamental for the biological domain: biological systems are organized natural systems that undergo (functional) variation.
In this paper, we provide a specific characterization of each principle, by emphasizing their mutual relations: organization provides the relevant kind of complexity for functional variation to occur; in turn, variation enables the maintenance of organization over time, notably at the evolutionary scale. We will illustrate this discussion with examples from plant morphogenesis.