The document discusses the BAM (Biotic, Abiotic, Movement) diagram, which is a heuristic for conceptualizing species' ecological niches and geographic distributions. It describes the three components of the BAM diagram - the abiotic niche defined by physiological requirements, the biotic niche defined by biotic interactions, and accessibility defined by a species' ability to disperse. The document also discusses Hutchinson's distinction between scenopoetic and bionomic variables and provides examples demonstrating the importance of dispersal limitations on species' distributions.