Since the advent of the theory of evolutio n, o ne of the tasks of biology has bee n to i nvestigate the phyloge netic relatio nship betwee n species. This task is especially impor ta nt because all of the differe nces which exist betwee n species, whether i n morphology, physiology , or ecology, i n ways of behavior, or even i n geographical distributio n, have evolved , like the species thems...

Biological systematics encompasses three distinct activities: taxonomy, classification (which may or may not be a reasonable reflection of phylogeny) and nomenclature (Fig. 1). Although systematists rigorously and distinctly practice these three components, they are often amalgamated under the term “taxonomy.” While the breadth of “taxonomy” is clearly understood among most practitioners, it ca...

iran contains 33 named endemic fish species, which together with undescribed taxa, approximates one-third of the ichthyofauna. endemism in relatively large species such as fishes, which are better known systematically than other taxa, can often serve to indicate areas in need conservation. an analysis of endemicity is given in terms of systematics, distribution and ecology.

the systematics, morphology, distribution, biology, economic importance and conservation of the freshwater eel ( anguilla anguilla ) of iran are described, the species is illustrated, and a bibliography on this fish in iran is provided. the species is found in the caspian sea basin as an exotic.

The systematics of the even light Po isotopes (N 126) are studied in the framework of the Particle-Core Model. The strong perturbation of the systematics in the very light isotopes is interpreted as arising from the interaction between regular and intruder structures. Results of Potential Energy Surface (PES) calculations and predictions of the Pairing Vibration Model support this interpretatio...