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Animal Eyes$
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Michael F. Land and Dan-Eric Nilsson

Print publication date: 2012

Print ISBN-13: 9780199581139

Published to Oxford Scholarship Online: December 2013

DOI: 10.1093/acprof:oso/9780199581139.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 26 September 2021

The origin of vision

The origin of vision

Chapter:
(p.1) 1 The origin of vision
Source:
Animal Eyes
Author(s):

Michael F. Land

Dan-Eric Nilsson

Publisher:
Oxford University Press
DOI:10.1093/acprof:oso/9780199581139.003.0001

Most of the types of eye that we recognize today arose in a brief period during the Cambrian, about 530 million years ago. The development of better eyes coincided with increases in size, speed, and armour, as visually guided predation became a common way of life. Opsin-based light sensitivity evolved in a common ancestor of all animals. Transduction mechanisms diverged early, and in the common ancestor of bilaterian animals there were at least two different types. These molecular mechanisms and corresponding genetic control networks have been modified and co-opted to form the wide range of eyes of modern animals. Eye evolution is driven by the evolution of visual tasks. Early animals could only perform few and simple behavioural tasks based on light sensitivity, but over time some animal groups acquired a growing list of ever more complex visual tasks. This development has gone from non-directional light sensitivity, via directional photoreceptors combined with body movements, to coarse spatial vision, and then to finer spatial vision with focusing optics. The evolution of advanced eyes need not have taken huge periods of geological time. It has been estimated that evolution from a patch of photosensitive tissue to an eye resembling that of a fish could have taken as little as half a million years. Eye structures responsible for spatial vision in vertebrates, cephalopods, and arthropods have evolved independently, which is now reflected in different embryologic development of eyes in these groups, and in the fundamental distinction between single-chambered eyes and compound eyes.

Keywords:   opsin, Cambrian, evolution, common ancestor, light sensitivity, transduction, directional photoreceptors, spatial vision, single-chambered eyes, compound eyes

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