This book represents the first attempt to quantify environmental factors and life history traits that accelerate or decelerate species diversity in animals. About 15%, 8% and 77% of species are distributed in marine (70% of earth's surface), freshwater (< 1%) and terrestrial (~ 29%) habitats. Hence, the terra firma fosters more diversity. The harsh hadal, desert and elevated montane habitats restrict diversity to 0.5-4.2%. Costing more time and energy, osmotrophic and suspension modes of food acquisition limit diversity to < 20%. In minor phyletics, evolution has proceeded from a 'wrong combination' of low motility and gonochorism to sessility and hermaphroditism. The motile major phyletics are more speciose (166,279 species/phylum) than the latter (1,975 species/phylum). As evolution and speciation are driven by motility, sessility is limited to 2.9% animals.

Selfing hermaphrodites (0.9%), parthenogens ( 96%), spermatozoan (81%) rather than spermatophore mechanism of sperm transfer, promiscuity and polygamy over monogamy, iteroparity (99.6%) over semelparity and internal fertilization (84%) are preferred, as they accelerate diversity. Body size and egg size determine fecundity. Indirect life cycle (82%) and incorporation of feeding larval stages accelerate diversity. Brooding and viviparity (6.4%) decelerate it. Parasitism extends life span and liberates fecundity from eutelism.

Evolution is an ongoing process, and speciation and extinction are its unavoidable by-products. The in-built conservation mechanism of reviving life after a sleeping duration has been reduced from a few million years in microbial spores to a few thousand years in plant seeds and a few hundred years in dormant eggs in animals. Hence, animal conservation requires priority. The existence of temperature-resistant/insensitive individuals, strains and species shall flourish during the ongoing global warming and earth shall continue with such burgeoning species, hopefully inclusive of man.