The biosphere of Persia is divided into several ecosystems, determined mainly by geographical (climatic differentiation, topography, soil type, etc.) and biological (vegetation, wild life, etc.) factors. Five primary ecological regions may be distinguished in Persia, each with a characteristic combination of features: the Caspian lowlands, the Alborz system and mountain ranges in Khorasan, the Persian plateau, the Zagros system with the Makrān mountain ranges, and the lowlands along the Persian Gulf.

Wildlife of Iran is diverse and composed of several animal species including bears, gazelles, wild pigs, wolves, jackals, panthers, Eurasian lynx, and foxes. Domestic animals include, sheep, goats, cattle, horses, water buffalo, donkeys, and camels. The pheasant, partridge, stork, eagles and falcon are also native to Iran.

As of 2001, 20 of Iran’s mammal species and 14 bird species are endangered. Among them are the Baluchistan bear (Ursus thibetanus gedrosianus), a subspecies of Asian Black Bear, Persian fallow deer, Siberian Crane, hawksbill turtle, green turtle, Oxus cobra, Latifi’s viper, dugong and dolphins. The Asiatic Cheetah is a critically endangered species which extinct elsewhere and now can only be found in Iran.

Wildlife of Iran, includes leopards, bears, hyenas, wild boars, ibex, gazelles, and mouflons, which live in the wooded mountains. Jackals and rabbits are common in the country’s interior. Wild asses live in the Kavirs. Cheetahs and pheasants are found in the Caspian region, and partridges live in most parts of the country. Aquatic birds such as seagulls, ducks, and geese live on the shores of the Caspian Sea and the Persian Gulf, while buzzards nest in the desert. Deer, hedgehogs, foxes, and 22 species of rodents live in semidesert, high-elevation regions. Palm squirrels, Asiatic black bears, and tigers are found in Baluchistan. Tigers also once inhabited the forests of the Caspian region but are now assumed to be extinct.

Iran possesses a very rich and diverse bird fauna, due to the great range of habitats and Iran’s position at a crossroads between three major faunal regions. The native fresh-water fishes of Persia include 155 species in 24 families and the Persian fauna includes seventy-five species and subspecies of snake.