Assertion: Each organelle has a specific function in the cell.
Reason: An organ is a group of tissues which perform a similar function.
Both the assertion and reason are true and the reason is not the correct explanation for assertion.
Organelles are specialized membrane-bound structures found in a cell with definite functions. Organs are a group of tissues which perform a similar function in the body of an organism. Just as different organs perform different functions in an organism, different organelles perform different functions in the cell. Except for the similarity in function at different levels, there's no direct connection. Hence, the reason is not the explanation for the assertion.