geographical and reproduction isolation of organism gradually need to speciation justify the statement it is too urgent!!!
Answers
Geographical isolation is a major factor in the speciation of organisms that reproduce sexually because it interrupts with gene flow. In most of the cases, gene flow must be stopped so that sub-populations become genetically isolated. Changes in allele and genotype frequencies within the populations, as a result of the effect of natural selection on the range of phenotypes produced by mutation and sexual recombination, lead to the formation of races and sub-species. Continued genetic isolation leads to the formation of new species. Geographical barriers such as mountain ranges, seas or rivers may produce a barrier to gene flow and the inability of organisms or their gametes to meet leads to reproductive isolation and hence, speciation.
However, geographical isolation may not have any effect in case of self-pollinating or asexually reproducing plant species as they do not depend on other organisms for reproduction.