The relationship between the area of a habitat, or of part of a habitat, and the number of species found within that area is described by the species-area curve. It says that log S = log C + Z log A. Here S is the number of species, A is the habitat area, and Z is the slope of the species-area relationship. Larger areas tend to contain larger numbers of species. So, the correct answer is 'log S = log C + Z log A'.