Generally speaking, speciation occurs more rapidly as you go down the evolutionary chain. Bacteria evolve new species rapidly, sometimes in a few years. Large mammals (as in whales and bears) and large predatory birds (as in hawks and condors) may not produce a recognisable new species for thousands of years. In the mean time, more go extinct than appear.

Most species on Earth are invertebrate animals: the insects, spiders and mites. They are all evolving new species at a rate somewhere between that of one-celled creatures and that of the large relic species. Most speciation requires when populations be separated by distance enough to prevent the exchange of genetic material. Islands and mountain tops (and caves) that are uninhabited (by humans) have huge numbers of undescribed species of both plants and animals. They are also usually small area and the species are vulnerable, especially to habitat destruction and from the ravages of new (pest) species such as rats that man brings with him.