What factors could lead to the rise of a new species?

Various factors that could lead to formation of new species are Geographical barrier, natural selection, genetic drift, and variations.

Geographical barrier-if sexually reproducing organisms are isolated by geographical barrier then the gene flow through gametes stops and the isolated members interbreed thus leading to the formation of new species.

Variations by Natural Selection- Nature select individuals that are better adapted to the environment. The organisms that are better adapted survive and reproduce more, whereas the organisms that are not adapted well to the environmental conditions are slowly erased from the environment.

Genetic drift- genetic drift is changes in the relative frequency of particular genes which which leads to disappearance of those genes as individuals either die or they do not reproduce