I presume you mean, how does a new species form?...
A group of one species get seperated from another, and circumstance change. shall we say... the tempertature rises? this one group (in a high temperature) will have an advantage if they have less fur, for they will not be as hot, therefore they become 'desirable mates' and through many generations the species has less fur, becoming an altogether seperate species than it started
Yes, geographic barriers guarantee the formation of new species.
macroevolution
Reproductive variation.
DNA
Yes, directional selection can lead to the formation of a new species by favoring certain traits within a population, eventually causing enough genetic divergence to create a new species.
the formation of species
speciation
The development of a new species through evolution is called speciation.
IT's means formation about a speciale craft....
the formation of a new species over a few generations
The general term for the process by which new species form is "speciation." Speciation occurs when populations of a species become isolated and diverge through various mechanisms, leading to genetic and phenotypic differences that eventually result in the formation of distinct species.
Allopatric Speciation (geographic isolation) can lead to the formation of a new species because the population is split in two smaller populations by a physical barrier (river, canyon, mountain...).