{"id":2627,"date":"2025-05-19T10:05:09","date_gmt":"2025-05-19T09:05:09","guid":{"rendered":"https:\/\/myknowledgehub.org\/?page_id=2627"},"modified":"2025-05-20T04:35:44","modified_gmt":"2025-05-20T03:35:44","slug":"chapter_3_3","status":"publish","type":"page","link":"https:\/\/myknowledgehub.org\/index.php\/evb_home\/modules_theory\/chapter_3_3\/","title":{"rendered":"EVB Chapter_3_3"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-page\" data-elementor-id=\"2627\" class=\"elementor elementor-2627\">\n\t\t\t\t<div class=\"elementor-element elementor-element-7bad944 e-flex e-con-boxed e-con e-parent\" data-id=\"7bad944\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-dead2f1 elementor-widget elementor-widget-spacer\" data-id=\"dead2f1\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-6f8f7e8 e-flex e-con-boxed e-con e-parent\" data-id=\"6f8f7e8\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-c9db006 elementor-widget elementor-widget-heading\" data-id=\"c9db006\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Chapter 3.3\n<br>\nEye in Vertebrates (Aves and Mammals)<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-9cbb10c e-flex e-con-boxed e-con e-parent\" data-id=\"9cbb10c\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-3b640fc elementor-widget elementor-widget-spacer\" data-id=\"3b640fc\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-a38fb1b e-flex e-con-boxed e-con e-parent\" data-id=\"a38fb1b\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-c76b677 elementor-widget elementor-widget-heading\" data-id=\"c76b677\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h4 class=\"elementor-heading-title elementor-size-default\">A. Structure and Function of Eye in Different Classes<\/h4>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-c125d08 e-flex e-con-boxed e-con e-parent\" data-id=\"c125d08\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-8ccba27 elementor-widget elementor-widget-image\" data-id=\"8ccba27\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/myknowledgehub.org\/wp-content\/uploads\/2025\/05\/gdc6ad6231bbf8da69ad6b842e9dce8cf99037a785d463220854a3899cd13deb511c2cf9a882ae733578c3eb9eae05f171cc814e674ddc158dec9a354ebb95007_1280-4559763-1024x683.jpg\" class=\"attachment-large size-large wp-image-2630\" alt=\"eye, girl, human, sight, vision, macro, beauty, eye, eye, eye, eye, eye\" srcset=\"https:\/\/myknowledgehub.org\/wp-content\/uploads\/2025\/05\/gdc6ad6231bbf8da69ad6b842e9dce8cf99037a785d463220854a3899cd13deb511c2cf9a882ae733578c3eb9eae05f171cc814e674ddc158dec9a354ebb95007_1280-4559763-1024x683.jpg 1024w, https:\/\/myknowledgehub.org\/wp-content\/uploads\/2025\/05\/gdc6ad6231bbf8da69ad6b842e9dce8cf99037a785d463220854a3899cd13deb511c2cf9a882ae733578c3eb9eae05f171cc814e674ddc158dec9a354ebb95007_1280-4559763-300x200.jpg 300w, https:\/\/myknowledgehub.org\/wp-content\/uploads\/2025\/05\/gdc6ad6231bbf8da69ad6b842e9dce8cf99037a785d463220854a3899cd13deb511c2cf9a882ae733578c3eb9eae05f171cc814e674ddc158dec9a354ebb95007_1280-4559763-768x512.jpg 768w, https:\/\/myknowledgehub.org\/wp-content\/uploads\/2025\/05\/gdc6ad6231bbf8da69ad6b842e9dce8cf99037a785d463220854a3899cd13deb511c2cf9a882ae733578c3eb9eae05f171cc814e674ddc158dec9a354ebb95007_1280-4559763.jpg 1280w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-8f68ff9 e-flex e-con-boxed e-con e-parent\" data-id=\"8f68ff9\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-c20e71a elementor-widget elementor-widget-text-editor\" data-id=\"c20e71a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h6><span style=\"color: #0000ff;\"><strong>Introduction<\/strong> <\/span><\/h6><p><strong>Definition and Evolutionary Significance<\/strong><br \/>The vertebrate eye is a <strong>complex sensory organ <\/strong>that detects light and converts it into electrochemical impulses, enabling vision. Its evolution represents one of the most remarkable examples of <strong>functional convergence<\/strong>, with camera-type eyes appearing independently in vertebrates and cephalopods.<\/p><p>\u00a0<\/p><h6><span style=\"color: #0000ff;\"><strong>I. General Structure of the Vertebrate Eye<\/strong><\/span><\/h6><p>1. <strong>Cornea<\/strong>: Transparent outer layer that refracts light. <br \/>2. <strong>Lens<\/strong>: Focuses light onto the retina. <br \/>3. <strong>Retina<\/strong>: Contains photoreceptors (rods for low light, cones for colour). <br \/>4. <strong>Optic Nerve<\/strong>: Transmits visual information to the brain. <br \/>5. <strong>Accessory Structures<\/strong>: Iris (controls pupil size), sclera (protective outer layer).<\/p><p>\u00a0<\/p><h6><span style=\"color: #0000ff;\"><strong><span style=\"font-size: 16px;\">II. The Avian Eye: Structure and Adaptations<\/span><\/strong><\/span><\/h6><p><strong>General Anatomy<\/strong><\/p><ul><li><strong>Large eyes relative to skull size <\/strong>(e.g., owls\u2019 eyes occupy 50% of skull volume). <\/li><li><strong>Pecten oculi<\/strong>: A vascular structure supplying nutrients to the retina (absent in mammals). <\/li><li><strong>Nictitating membrane<\/strong>: A translucent third eyelid for protection.<\/li><\/ul><p><strong>Diurnal Birds<\/strong> (e.g., Eagles, Hawks)<\/p><ul><li><strong>High cone density <\/strong>for exceptional daytime vision. <\/li><li><strong>Fovea centralis<\/strong>: A deep pit in the retina for extreme acuity (eagles have <strong>2x human visual resolution<\/strong>). <\/li><li><strong>Tetrachromatic vision<\/strong>: UV-sensitive cones enhance prey detection.<\/li><\/ul><p><strong>Nocturnal Birds<\/strong> (e.g., Owls)<\/p><ul><li><strong>Rod-dominated retinas <\/strong>for superior night vision. <\/li><li><strong>Tubular eye shape <\/strong>maximizes light capture. <\/li><li><strong>Asymmetrical ears + binocular vision <\/strong>for precise prey localization.<\/li><\/ul><p><strong>Aquatic Birds<\/strong> (e.g., Penguins, Cormorants)<\/p><ul><li><strong>Flat corneas <\/strong>for underwater focus. <\/li><li><strong>Red oil droplets <\/strong>in cones enhance contrast in dim waters.<\/li><\/ul><p>\u00a0<\/p><h6><span style=\"color: #0000ff;\"><strong>III. The Mammalian Eye: Structure and Adaptations<\/strong><\/span><\/h6><p><strong>General Anatomy<\/strong><\/p><ul><li><strong>Less variation in eye shape<\/strong>\u00a0compared to birds. <\/li><li><strong>Tapetum lucidum <\/strong>in nocturnal species (reflects light for enhanced night vision).<\/li><\/ul><p>\u00a0<\/p><p><strong>Primates<\/strong> (High-Acuity Vision)<\/p><ul><li><strong>Trichromatic vision<\/strong> (red, green, blue cones) in Old World monkeys and apes. <\/li><li><strong>Fovea specialization <\/strong>for detailed object recognition.<\/li><\/ul><p><strong>Nocturnal Mammals<\/strong> (e.g., Cats, Bats)<\/p><ul><li><strong>Tapetum lucidum<\/strong>\u00a0causes eyeshine. <\/li><li><strong>High rod-to-cone ratio <\/strong>(cats: 25:1).<\/li><\/ul><p><strong>Aquatic Mammals<\/strong> (e.g., Dolphins, Seals)<\/p><ul><li><strong>Spherical lenses<\/strong> for underwater focus. <\/li><li><strong>Corneal flattening <\/strong>reduces refractive error when surfacing.<\/li><\/ul><p><strong>Ungulates and Prey Species<\/strong> (e.g., Deer, Horses)<\/p><ul><li><strong>Horizontal pupils <\/strong>expand panoramic vision (300\u00b0 field of view). <\/li><li><strong>Limited colour vision<\/strong>\u00a0(dichromatic).<\/li><\/ul><p>\u00a0<\/p><h6><span style=\"color: #0000ff;\"><strong><span style=\"font-size: 16px;\">IV. Comparative Analysis of Avian and Mammalian Vision<\/span><\/strong><\/span><\/h6><p><img decoding=\"async\" class=\"alignnone wp-image-2629 size-full\" src=\"http:\/\/myknowledgehub.org\/wp-content\/uploads\/2025\/05\/Table-11.png\" alt=\"\" width=\"922\" height=\"289\" srcset=\"https:\/\/myknowledgehub.org\/wp-content\/uploads\/2025\/05\/Table-11.png 922w, https:\/\/myknowledgehub.org\/wp-content\/uploads\/2025\/05\/Table-11-300x94.png 300w, https:\/\/myknowledgehub.org\/wp-content\/uploads\/2025\/05\/Table-11-768x241.png 768w\" sizes=\"(max-width: 922px) 100vw, 922px\" \/><\/p><h6>\u00a0<\/h6><h6><span style=\"color: #0000ff;\"><strong>IV. Major Evolutionary Milestones in Vertebrate Eye Development<\/strong><\/span><\/h6><p>1. <strong>Early Vertebrates<\/strong> (~500 MYA):<\/p><ul><li>Evolution of <strong>camera-type eyes <\/strong>from light-sensitive patches.<\/li><\/ul><p>2. <strong>Mesozoic Birds<\/strong> (~160 MYA):<\/p><ul><li>Development of <strong>foveae and pecten oculi <\/strong>for flight precision.<\/li><\/ul><p>3. <strong>Nocturnal Adaptations<\/strong> (~100 MYA):<\/p><ul><li><strong>Tapetum lucidum <\/strong>in mammals; <strong>rod specialization<\/strong> in owls.<\/li><\/ul><p>4. <strong>Aquatic Adaptations<\/strong> (~50 MYA):<\/p><ul><li><strong>Spherical lenses <\/strong>in cetaceans and pinnipeds.<\/li><\/ul><h6>\u00a0<\/h6><h6><span style=\"color: #0000ff;\"><strong>Conclusion<\/strong><\/span><\/h6><p>The vertebrate eye demonstrates <strong>extraordinary adaptive diversity<\/strong>, from the UV-sensitive retinas of birds to the light-amplifying tapeta of nocturnal mammals. Key evolutionary trends include: i) <strong>enhanced acuity <\/strong>in predatory birds and primates, ii) <strong>spectral sensitivity expansions<\/strong> (UV in birds, IR in some snakes), and iii) <strong>ecological specialization <\/strong>(aquatic flattening, nocturnal tubular eyes).<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-2821eb8 e-flex e-con-boxed e-con e-parent\" data-id=\"2821eb8\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-c7a0925 elementor-align-center elementor-widget elementor-widget-button\" data-id=\"c7a0925\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"button.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"elementor-button-wrapper\">\n\t\t\t\t\t<a class=\"elementor-button elementor-button-link elementor-size-sm\" href=\"https:\/\/myknowledgehub.org\/index.php\/evb_home\/modules_theory\/\">\n\t\t\t\t\t\t<span class=\"elementor-button-content-wrapper\">\n\t\t\t\t\t\t\t\t\t<span class=\"elementor-button-text\">Back to Theory Modules<\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Chapter 3.3 Eye in Vertebrates (Aves and Mammals) A. Structure and Function of Eye in Different Classes Introduction Definition and Evolutionary SignificanceThe vertebrate eye is a complex sensory organ that detects light and converts it into electrochemical impulses, enabling vision. Its evolution represents one of the most remarkable examples of functional convergence, with camera-type eyes &hellip;<\/p>\n<p class=\"read-more\"> <a class=\"\" href=\"https:\/\/myknowledgehub.org\/index.php\/evb_home\/modules_theory\/chapter_3_3\/\"> <span class=\"screen-reader-text\">EVB Chapter_3_3<\/span> Read More &raquo;<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2437,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"site-sidebar-layout":"no-sidebar","site-content-layout":"page-builder","ast-site-content-layout":"full-width-container","site-content-style":"unboxed","site-sidebar-style":"unboxed","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"disabled","ast-breadcrumbs-content":"","ast-featured-img":"disabled","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","footnotes":""},"class_list":["post-2627","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/myknowledgehub.org\/index.php\/wp-json\/wp\/v2\/pages\/2627","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/myknowledgehub.org\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/myknowledgehub.org\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/myknowledgehub.org\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/myknowledgehub.org\/index.php\/wp-json\/wp\/v2\/comments?post=2627"}],"version-history":[{"count":7,"href":"https:\/\/myknowledgehub.org\/index.php\/wp-json\/wp\/v2\/pages\/2627\/revisions"}],"predecessor-version":[{"id":2636,"href":"https:\/\/myknowledgehub.org\/index.php\/wp-json\/wp\/v2\/pages\/2627\/revisions\/2636"}],"up":[{"embeddable":true,"href":"https:\/\/myknowledgehub.org\/index.php\/wp-json\/wp\/v2\/pages\/2437"}],"wp:attachment":[{"href":"https:\/\/myknowledgehub.org\/index.php\/wp-json\/wp\/v2\/media?parent=2627"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}