Ed Yong’s new piece in National Geographic on the evolution of eyes across different branches of animal life is a great one: “Inside the Eye: Nature’s Most Exquisite Creation”. Awesome photographic comparisons of eyes from different kinds of creatures and discussion of their evolutionary diversity.
The same can’t be said for other eye components. Take lenses. Almost all of them are made from proteins called crystallins, which improve their owners’ vision by focusing light onto underlying photoreceptors. But unlike opsins, with their single dynasty, crystallins are unified by name only. Yours are unrelated to those of a squid or a fly. Different animal groups have independently evolved their own brand of crystallins by co-opting proteins that had very different jobs, unrelated to vision: Some broke down alcohol; others dealt with stress. But all were stable, easy to pack, and capable of bending light—perfect for making lenses.
The eye is the evolutionary gift that keeps on giving to those of us who teach about homology and convergence.