Geographical isolation means separation of species by physical barriers like water forms, oceans, mountains etc. Geographical isolation just requires single parent. The offspring is just an exact copy of the parent. As there are less chances for variations to occur, new species are not formed in asexually reproducing individuals undergoing geographic isolation.

Geographical isolation is when diffrences occur in the same area due to some natural calamity or some other due to some other reason between two our more species and two different species can\’t reproduce with one another and variation donot occur.
It means separation of species by physical barriers like mountains,oceans,etc.
When a species divides into two different ones by residing in different places having different climate.. Like bears…. And polar bears
This is not in syllabus and you are from 12

Geographical isolation means seperation of species by physical barriers like water forms, mountains,etc
,what is geographical isolation

Reproductive isolation due to geographical barriers like river, forest