What would have happened ? If.............

There had been no difference between mitochondria and plastids.

Mitochondria are found in both plants and animal cells while Plastids are found only in plant cells.

Both of these organelles differ in their functions since,

Beside these dissimilarities, there are more similarities among both organelles,

Like both are double membrane-bound, both have their own genetic material, both have 70s ribosomes, both help in different forms of energy production.

If there would have been no difference between both, then the functions performed by them would have not been possible because during photosynthesis oxygen is evolved out as the end product from plastids and during oxidation of molecules in mitochondria oxygen is consumed (as an electron acceptor).

Thus, oxygen evolved would have been consumed by the plants themselves and life might have not existed on earth.