Biology'1B'–'Evolution'Lectur e'12''–''species'sel ection'(macroevol),'transitional'forms,'evolution'of'novel'phenotypes' Species selection Traits'that'arise' via'micro evolution'can'also'act'to'increase'net'speciation'rate'('='Speciation'rate' –'Extinction'rate).''Traits'that'increase'sp eciation 'rat e'and/or'decrease'extinction'rate'in'a'clade'of 'species'can'be'id enitifed'through'comparison'of'closely'relat ed'clades,'especia lly'if'trait'arises'repeatedly'and'is'consistently'as sociated'with'high'species'diversity'in'those'clades'relative'to'sister'clades'that'la ck'this'trait'(se e'Figure'fr om'Rabosky'&'McCune'2010).'The'power'of'species'selec tion,'relative'to'individual‐based'selection'within'species,'is'clearest'when'traits'that'are'disadvantageous'with in'speci es'are'associated'with'increased'net'speciation'among'clades'–'ie.'op posing'effects.'Exam ple'–'evolution'of'self‐compatibility'(SC;'ability'to'self‐fertilize)'in' m onoecious'plants'vs,'self‐incompatibility'(SI,'no'self'fertilization).''SI'can'be'a'dis advantage'within'species'if'pollinators'ar e'limiting''‐'in'this'circumstance,'SC'allows'reprodu ction.''But'in'the'longer‐term'SC'increased'rate'of 'inbreeding,'loss'of'genetic'diversity'etc'= >'higher'extinction'rat es.'SC'has'arisen'repeatedly'in'flowering'plants'(eg.'Figure'for'Solanaceae'(tomatoes'&'relatives )),'but'analysis'of'phylogenies'suggest'that'it'leads'to'higher'ext inction'rates'of'species,'despite'short‐term 'advantage'to'individuals.'Thus,'clades 'with'SI'have'more'species'surviving'than'those'with'SC.' The fossil record: transitional forms Comparison'of'extant'(living'forms)'=>'predictions'of''evolution arily'transitional'phenotypes'in'the'fossil'record' Major Transitions in Phenotypes 'e.g.'Vertebrate'Fish'' '''''' '''Amphibian'Tetrapods''[see'next'page]'Biology'1B'–'Evolution'Lectur e'12''–''species'sel ection'(macroevol),'transitional'forms,'evolution'of'novel'phenotypes''' ' ' ' ' ' ''''''Figure'34.20'(page'711,'8th'edition)'' ' ' ' '• There'is'a'huge'jump'between'these'groups'(particular ly'in'p henotypes),'which'cannot'be'construc ted'from'modern'fauna—this'is'where'the'fossil'recor d'comes'into'play'• The'transition'from'ancestors'of'lungfish'to'ancestors'of'tetrapo ds,'and'key'insights'are'coming'from'fossils''--Acanthostega has a moving neck, lungs, limbs, but no wrists and a weak rib cage that would have made breathing on land very difficult, so it probably lived in a swamp --Tiktaalik, however, has the evolved traits of Acanthostega plus wrists and a stronger rib cage (see image below) • The'extinct'forms'are'not'necessarily'direct'anc es tors,'but'they'do 'allow'us'to'see'how'a nd'when'certain'traits/adaptations'evolved'''Evolution of Novel Structures and Exaptation • The'hammer'and'anvil'bones'of'the'middle'ear'of'mammals'that'act'as'transmitters'from'the'outer'ear'into'the'inner'ear'• There'is'a'complete'set'of'fossil'transitions'that'takes'us'from'the'original'function'of'the'bones'(articulation'points'of'the'jaw)'in'cynodonts'and'synapsids'Point'of'transition'from'exclusively'aquatic'organisms'to'terrestrial'vertebrates'is'imp ortant'Biology'1B'–'Evolution'Lectur e'12''–''species'sel ection'(macroevol),'transitional'forms,'evolution'of'novel'phenotypes''Figure'34.31'(page'721,'8th'edition),'see'also'Figure'25.6'(page'513,'8th'edition)''• Co‐opting'structures'from'one'function'to'another'is'known'as'exaptation'(don’t'need'a'new'structure'to'arise ,'can'simply'modify'an'existing'one)'• Feathers'are'another'example—their'original'purpose'may'not'h ave'been'for'flight,'but'rather'for'attracting'mates'or'thermoregulation'‐‐new'studies'have'found'dinosaurs'with'feathers'tha t'w ere'colored,'but'not'for'flight,'suggesting'their'use'in'display'Evolutionary Novelties—evo-devo • Re‐programming'of'developmental'pathwa ys'can'cause'changes'in'timing/location'of'expression'of'key'regulatory'gen es'• Within'sets'of'genes,'there'are'often'duplicates,'allowing'one'copy'to'be'kept'a nd'others'to'be'used'for'new'functions'Biology'1B'–'Evolution'Lectur e'12''–''species'sel ection'(macroevol),'transitional'forms,'evolution'of'novel'phenotypes''Figure'25.22'(page'527,'8th'edition)'• In'insects,'the'Ubx'gene'suppresses'leg'development'to'6'legs,'but'it 'can'have'a'different'effect'in'other'species''• Very'different,'but'homologous'structures'typically'have'a 'common'site'of'developmental'genes''''These'structures'have'very'differen
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