We thus implemented the level set method (Sethian, 1999) in Python to detect the exact surface of the meristem: a suitable surface obtained by the thresholding of the image is evolved to the smooth surface that is the most accurate representation of the surface contrast in the 3D images.
Essentially, the part of the domain where the signal is below S2ends up at a steady state on the lower branch of the bifurcation diagram, while that part of the domain which is subject to a signal above the threshold evolves to the elevated, unique steady state.
However, Maynard Smith's model argues that natural selection favours a situation in which all traits evolve to the same trait values relative to their specific critical thresholds.
The immune system has evolved to defend the organism against a variety of pathogens and applies threshold mechanisms for regulation.
These orphans are not "real" orphans but evolving to quick for the threshold of similarity to catch them.
Communities on clumped fractal landscapes evolved to (or got stuck at) the critical biodiversity threshold, whereas communities with an intermediate degree of order (H = 0.5) generally evolved beyond this point and attained a high level of species richness.
In less than 4,000 generations, both thresholds evolved to zero levels (Fig. 2a, b).
