Answer: The given statement is True.
According to competitive exclusion principle-
Two species, which compete for the same limiting resource (like food) in a particular area can not exist together. The species having slighter advantage over the other will survive and exclude the other one. In other words, the other species will either extinct or move to some other niche.
This is also called Gause's principle.
Thus, the given statement that two organisms cannot fill the same niche is true according to this principle.