Immunology and Reproduction
The relationship between a living organism and its environment is based on a tightly regulated balance between symbiosis and competition. Survival is dependent upon appropriate resource acquisition, permissive physicochemical environments, and competition for limiting resources and ecological niches exerted by other living organisms. The complexity of an organism is directly correlated to the sheer volume of challenges presented to its continued fertility (the ultimate currency of evolution). Generally, competition can be extra-organismal (acquisition of the same resource by competing organisms), interorganismal (direct predation), or intraorganismal (parasitism). The evolution of higher organisms required the development of advanced defense mechanisms to ensure survival in an overwhelmingly hostile biological environment. The systems in higher organisms that protect against biological insults are collectively referred to as the immune system. The immune system may act as friend or foe. Immune systems of higher vertebrates can be roughly subdivided into two major components: a phylogenetically older innate immune system and the more recently evolved adaptive immune system. Innate immunity is a genetically fixed, direct evolutionary relative of the ancient mechanisms of niche competition found in both plants and animals. The diversity of environments that humans occupy is staggering; thus, the human body has remarkably elaborate mechanisms to protect the individual from foreign pathogens..
