As organisms evolve to take better advantage of their surroundings, they may come into competition. A predator may compete with its prey, or two species eating the same plant may compete with one another to find it. With only a limited amount of resources to go around, living things have to adapt not only to climate, geography, and other slow-changing variables but also to the more rapid evolutionary changes undertaken by their competitors. Although change in climate can be seen as a comparatively slow change, one's living competitors are constantly evolving, and this requires that both parties keep on their respective toes: Fighting for resources can be a never-ending battle, and evolution ensures that the playing field is rarely level. However, evolution does not necessary breed outright competition, as it is also possible for two species to enter a mutually beneficial relationship whereby they help each other. No...