"One hundred and twenty-five years [after the publication of Charles Darwin's masterpiece, On the Origin of Species], we know a lot more about animals and plants than Darwin did, and still not a single case is known to me of a complex organ that could not have been formed by numerous successive slight modifications. I do not believe that such a case will ever be found. If it is -- it'll have to be a really complex organ, and... you have to be sophisticated about what you mean by 'slight' -- I shall cease to believe in Darwinism." [Richard Dawkins, The Blind Watchmaker, p.91]
Physics books may be complicated, but ... the objects and phenomena that a physics book describes are simpler than a single cell in the body of its author. And the author consists of trillions of those cells, many of them different from each other, organized with intricate architecture and precision-engineering into a working machine capable of writing a book.... Each nucleus... contains a digitally coded database larger, in information content, that all 30 volumes of the Encyclopedia Britannica put together. And this figure is for each cell, not all the cells of the body put together.
To begin with, an ancestor like an ordinary squirrel, living up trees without any special gliding membrane, leaps across short gaps. [It could leap further if it had something to slow a fall.] So natural selection favors individuals with slightly pouchy skin around the arm or leg joints, and this becomes the norm.... Now any individuals with an even larger skin web can leap a few inches further. So in later generations this extension of skin becomes the norm, and so on.... It is easy to imagine true flapping flight evolving from repetition of the muscular movements used to control glide direction, so average time to landing is gradually postponed over evolutionary time.
Some biologists, however, prefer to see long-distance downhill gliding as the dead end of the tree-jumping line of evolution. True flight, they think, began on the ground rather than up trees.... There are some mammals such as kangaroos that propel themselves very fast on two legs, leaving their arms free to evolve in other directions.... But bipedal mammals don't seem to have taken the next step and evolved the power of flight. The only true flying mammals are bats, and their wing membrane incorporates the back legs as well as the arms.... Perhaps birds began flying by leaping off the ground, while bats began by gliding out of trees. Or perhaps birds too began by gliding out of trees. The debate continues. [108-113]
When light first strikes the retina a photon interacts with a molecule called 11-cis retinal, which rearranges within picoseconds to trans-retinal. (A picosecond is about the time it takes light to travel the breadth of a single human hair.) The change in the shape of the retinal molecule forces a change in the shape of the protein, rhodopsin, to which the retinal is tightly bound. The protein's metamorphosis alters its behavior. Now called metarhodopsin II, the protein sticks to another protein, called transducin. Before bumping into metarhodopsin II, transducin had tightly bound a small molecule called GDP. But when transducin interacts with metarhodopsin II, the GDP falls off, and a molecule called GTP binds to transducin. (GTP is closely related to, but critically different from, GDP.)
"Molecular Machines: Experimental Support for the Design Inference" by Michael J. Behe
Information on Darwin's Black Box: The Biochemical Challenge to Evolution by Michael J. Behe