Question

if the number of tertiary consumers is increased more then it is necessary it cause the imbalance of ecosystem,how?

Answer 1

If the number of tertiary consumers increase then it imbalances whole food chain and also ecosystem, If tertiary consumer increase then secondary consumers will decreases and because of decrease in secondary consumers number of primary consumers will increase.
In ecosystem there are so many food chains present which converted in to food web and if in these food web number of tertiary consumers increase more than it necessary then it will impact on whole ecosystem and it will cause imbalance in ecosystem.

I Hope it is true....!