Evolution's Witness: How Eyes EvolvedWith predation and carnivory as catalysts, the first known eye appeared in a trilobite during the Cambrian explosion approximately 543 million years ago. This period was a crucible of evolution and teemed with anatomic creativity although the journey to formed vision actually began billions of years before that. The Cambrian period, however, spawned nearly all morphologic forms of the eye, followed by descent over hundreds of millions of years providing an unimaginable variety of eyes with at least ten different designs. Some eyes display spectacular creativity with mirror, scanning or telephoto optics. Some of these ocular designs are merely curiosities, while others offer the finest visual potential packed into a small space, limited only by the laws of diffraction or physiological optics. For example, some spiders developed tiny, well-formed eyes with scanning optics and three visual pigments; scallops have 40-100 eyes circling their mantle, each of which has mirror optics and contains two separate retinae per eye; deep ocean fish have eyes shaped like tubes containing yellow lenses to break camouflage; and some birds have vision five times better than ours; but this is only part of the story. Each animal alive today has an eye that fits is niche perfectly demonstrating the intimacy of the evolutionary process as no other organ could. The evolution of the eye is one of the best examples of Darwinian principles. Although few eyes fossilize in any significant manner, many details of this evolution are known and understood. From initial photoreception 3.75 billion years ago to early spatial recognition in the first cupped eyespot in Euglena to fully formed camera style eyes the size of beach balls in ichthyosaurs, animals have processed light to compete and survive in their respective niches. It is evolution's greatest gift and its greatest triumph. This is the story of the evolution of the eye. |
Contents
Molecular Genesis Hadean Eon 46003750 million years ago | 3 |
1 The Age of First Cellular Life Archean Eon 37502500 million years ago | 5 |
2 The Age of Complex Cellular Life Proterozoic Eon 2500543 million years ago Cryogenian Period 850650 million years ago Ediacaran Period 650... | 12 |
3 Eukaryotes Organize and Metazoans Arise Neoproterozoic Era 1000543 million years ago Cryogenian Period 850650 million years ago Ediacaran ... | 17 |
4 Early Animals Prepare the Ground Ediacaran Period 650543 million years ago | 25 |
5 Visions Big Bang Blazes the Trail Early Paleozoic Era Cambrian Explosion 543490 million years ago | 38 |
Paleozoic Era Cambrian Period 543490 million years ago | 50 |
7 Vertebrates Gain a Foothold Paleozoic Era Cambrian Period 543490 million years ago | 63 |
16 March of the Archosaurs Mesozoic Era Triassic Period 251208 million years ago Jurassic Period 208145 million years ago | 152 |
17 Dinosaurs and Their Companions Mesozoic Era Triassic Period 251208 million years ago Jurassic Period 208145 million years ago | 161 |
18 Cephalopods Change Direction Mesozoic Era Jurassic Period 208145 million years ago | 164 |
19 Snakes Arise from the Ground Mesozoic Era Cretaceous Period 14565 million years ago | 172 |
20 The Age of BirdsThe Eye Taken to Great Heights Mesozoic Era Cretaceous Period 14565 million years ago Cenozoic Era Tertiary Period 652 mil... | 176 |
21 Pollinators Coevolve Mesozoic Era Cretaceous Period 14565 million years ago Cenozoic Era Tertiary Period 652 million years ago | 202 |
22 Mammalia Diversifies Mesozoic Era Cretaceous Period 14565 million years ago Cenozoic Era Early to MidTertiary Period 6556 million years ago | 216 |
23 The Age of Mammals Mesozoic Era Late Cretaceous Period 10065 million years ago Cenozoic Era Tertiary Period 6518 million years ago Quater... | 224 |
8 Shelly Fauna Rule the Seas Paleozoic Era Ordovician Period 490445 million years ago | 70 |
9 The Piscine Eye Develops Paleozoic Era Silurian Period 445415 million years ago | 77 |
10 The Piscine Eye Matures Paleozoic Era Early Devonian Period 415398 million years ago | 85 |
11 Insects Arise to Fly Paleozoic Era Early Devonian Period 415398 million years ago | 109 |
12 Stealth Speed and Predation Paleozoic Era Devonian Period 415362 million years ago | 114 |
13 The Age of Tetrapods and Terrestrials Vertebrate Animalia Comes Ashore Paleozoic Era Late Devonian Period 385362 million years ago | 119 |
14 Terrestrial Life Flourishes Paleozoic Era Carboniferous Period 362299 million years ago Permian Period 299251 million years ago | 131 |
Mesozoic Era Triassic Period 251208 million years ago | 138 |
24 Planktonic Soup Evolves Cenozoic Era Tertiary Period 6518 million years ago Quaternary Period 18 million years ago to present | 230 |
25 Mammals Return to the Sea Cenozoic Era Tertiary Period 6518 million years ago Quaternary Period 18 million years ago to present | 235 |
26 The Visual Witness and a Conscious Brain Cenozoic Era Quaternary Period 18 million years ago to present | 240 |
Appendices | 243 |
Glossary | 265 |
Bibliography | 273 |
297 | |
Other editions - View all
Evolution's Witness: How Eyes Evolved Ivan R. Schwab,Richard R. Dubielzig,Charles Schobert No preview available - 2012 |
Common terms and phrases
accommodation acuity adaptations animals appeared apposition eye aquatic Archaea arthropods beetles birds bony brain Cambrian Chapter choroid ciliary color vision compound eyes cones cornea create creatures crystalline lens diapsids diurnal dorsal early Ediacaran elasmobranchs evolution evolutionary evolved extraocular muscles eyespot fish fossil fovea frogs genes gland globe hagfish ichthyosaurs illustrates Image by Richard insects invertebrates jellyfish lampreys last common ancestor layer lenses lids light lineage lizards mammals mechanisms metazoan microvillus mollusks neurologic niche nictitans nocturnal ocellus ocular oil droplets ommatidia ommatidium opsins optic nerve organisms photons photopigment photoreceptors placoderms predators prey primates probably proteins protists pupil radiated rays refraction reptiles reptilian retina rhabdom rhabdomeric rhodopsin Richard Dubielzig sclera sensory simple eyes snakes species spherical spiders squid stereopsis structure superposition eye surface synapsids tapetum terrestrial tetrapods theropods tion trilobites tuatara turtles vascular vertebrates visual field visual pigments visual witness wavelengths worms