Lets say you raise and someone calls you in position and he checks to you , Now of course you have to defend an x% frequency of your investment on the flop, that x% amount is unknown and it doesnt matter in this example but the question is if you choose to defend your investment by checking back then does your required defense ratio increases or decreases on the turn? or remain the same as your previous street?

For example you need to defend 70% of your preflop range on the flop and if you did that against a bet then you would need another 70% defense frequency of your flop range on the turn but since you defended by checking back then does this number drops or increases? or remain the same?

My english are bad , i hope you understand what i am asking.

Depends on why you checked back and the specific turn card. If you check back as a defensive measure with lots of bluffcatchers and weak draws, then particularly scary turn and river cards will cause you fold a lot of your range. If you were checking back as a slowplay with lots of strong hands, then particularly scary turns could force you to calldown instead of raising with your planned slowplay.

On dynamic boards that smash my opponent's range, I check back a lot of bluffcatchers and weak draws that don't have enough draw potential to semibluff.

On static boards that miss my opponent's range, I cbet more, but my checking range is filled with hands that hopefully earn more by checking than by betting like bluffcatchers and slowplays. In a no limit game, I'll have more slowplays than in a limit game. In a limit game, it's harder to make up missed bets, but in no limit the pot grows geometrically instead of linearly, which allows us to make up missed bets later in the hand.