Apopulation of animals is split in half by a river. before speciation is completed, the two halves are rejoined when a drought causes the river to run dry. how would this impact the two populations?

The gene flow would increment or quality stream would increment between the two parts, and speciation would not happen. The probability of speciation would diminish as qualities were shared between the two gatherings. Kept up quality stream between two populaces can likewise prompt a mix of the two quality pools, diminishing the hereditary variety between the two gatherings.

20000 as first it increases by 2500 then by 5000 so next it will increase by 10000