In Nature’s Arena, the first volume of The Rules of Coexistence, we embark on a journey to unravel one of nature's most fundamental forces. This book moves beyond the simple idea of 'survival of the fittest' to reveal a world of sophisticated strategies and profound consequences. You will discover the theoretical arena where life is possible—the fundamental niche—and witness how the brutal realities of the living world compress it into the realized niche. We will explore the mechanisms of battle, from the frantic scramble for resources to the direct contest of dominance and territoriality.