What will happen over time if a population of organisms from the same species is physically separated and can't reproduce with one another?

Not too sure about this but I think it would cause extinction  

Explanation:

Without reproduction, there would be no offsprings and eventually the older generation of that species would die out.

the  different  of  these  two  are  that  they  differently  handle  their  team.

an  expressive  leader  focuses  on  the  task  at  hand  and  make  sures  that  their  goal  is  achieved.  they  accurately  finish  the  task.  an  instrumental  leader  on  the  other  hand  works  on  the  unity  of  the  group,  they  care  more  about  their  employees.  all  the  while  creating  a  good  environment.