No, it isn't invisable or even invisible.
It all just cooks together inside the critter really knowing the critter needs to fly then one day, wings pop out it's butt and it commences to flapping.
You are extremely ignorant. Extremely. Why even pretend you care anything at all about science?
So if we say it takes millions of years (though we can't prove that anything has actually been around that long) then people will have to drop their expectation of ever seeing it happen and we can claim any bloody thing we like.. Yep. Snake oil. I thought this was supposed to be science. It's nothing more than a different religion trying to disprove God apparently. I don't see much science in it. There's a lot there pretending at science. But this is more like a debate between protestants and Catholics than a debate on science.
That isn't reasoning, that's typing. To a Witch Doctor, everything is My God versus Your God. Science reasons things in ways you don't understand and probably think you will go to Hell for understanding. That doesn't give us much to talk about or you much to say to a science class.