Evolution acts in:
Populations. One species can be scattered all around the world, but not because one population needs to change the other will have to as well.
Example:
Let´s tasy on species of ant lives in India and in the US, but only the US is having a drought problem, then, only the population in the US is obliged to change, which doesn´t affect the Indian population.
Hope it helped,
BioTeacher101
