Originally Posted by
cuppajoe_9
The pre-scorpion first develops a risistance to some sort of venom that is present in its environment. It then, over time, starts developing the poison in its own body as a defense against being eaten. Nature eventually selects those scorpions which collect the poison in a gland, as opposed to excreting it, because those would be more poisonous, and therefore less likely to be eaten. Eventually, the pre-scorpions develop the ability to eject the poison from their bodies, first as a defense mechanism, and then for the purposes of hunting. Nature selects for those scorpions which can hunt most efectively, and you wind up with something extremely scary.
There are plenty of reptiles who survive without the ability to change colours. The chameleon likely developed that trick out of necessity as his environment became increasingly multi-coloured, likely by flowers competing for the attention of insects.
Bats, despite their reputation, are not blind. Early bats probably hunted in the day, until they were forced by environmental pressures to develop the ability to do so at night. Better hearing is certainly an advantage when you can't see, and the echolocation probably developed in parallel with that.
The frog is an interesting one. Perhaps the ability to turn of the stomach acid developed first, maybe because this particular frog was suceptible to ulcers to the point where it affected its ability to procreate. Raising ones young inside one's self has obvious advantages in terms of chances of passing on one's genes.
I am not saying that this is definitely how these traits evolved, or even that it is probably how those traits evolved. All I'm saying as that, even if you can't imagine transitional forms for some creatures, I certainly can. That doesn't make me right, but it makes it true that transitional forms aren't impossible.