MrIzzz.. what is your goal anyways?? build muscle mass?
if so man, pushups and situps won't get you very far at all
if you're just looking to lose some fat or whatever it's fine if you do enough per day... it's mainly about diet in that situation.
but muscle mass, yeah you have to force your muscles to grow with significant resistance, bodyweight alone like pushups/situps isn't very much... you might notice some results initially - but you will quickly plateau once your body has adapted to the amount of stress pushups/situps is able to provide.