Lecture'19''Bio'200'''Lophotrochozoans:'• Coelomates'have'a'coelom''lined'with'muscular'tissue'(mesoderm)'• The'internal'organs'are'surrounded'by'muscle'• The'musculature'gives'the'coelomates'much'better'control'over'their'movements.'''SegmentationD''• Even'though'segmentation'has'evolved'multiple'times,'it'is'particularly'topical'when'you'talk'segmented'worms.''• Important'advance'in'animal'body'plant'• It'allows'for'specialization'and'development'of'individual'parts'of'the'animal,'like'reproduction,'digestion'excretion,'feeding,'respiration,'locomotion'• The'different'segments'in'these'animals'can'house'different'organs'or'perform'different'functions.'''Annelids:'• Lophotrochozoans'• Segmented'worms'• Annelid'segments'are'stack'of'hollow'rings.'• The'segments'are'divided'by'septate'• In'each'of'the'rings,'there'are'or'organs'for'excretion'or'locomotion.'• This'repetition'protects'an'annelid'from'physical'damage.''• The'annelid’s'ceoloms'function'as'a'hydrostatic'skeleton.''• Because'of'the'extra'musculature'that'we'see'in'the'body'cavity'because'these'are'coelomates,'each'of'these'segments'can'expand'or'contract'independently'which'then'will'then'allow'for'much'more'complexity'and'movement'then'what'we'see'in'a'cytocelomate'worm'that'also'has'hydrostatic'skeleton.''• The'interior'segments'have'specialized'sensory'organs'• Some'are'sensitive'to'light'and'some'have'even'elaborate'eyes'• A'well'develop'cerebral'ganglia/brain'is'present'in'the'very'front'• We'start'getting'to'animals'with'something'like'a'brain'• There'are'two'classes'of'Annelids:'Earthworms/Leeches'and'Polychaetes'DEarthworms'live'underground,'so'they'have'lost'their'eyes'• They'have'other'highly'developed'sensory'division'• The'leeches'group'with'the'earthworms'and'leeches'are'known'for'sucking'blood'or'other'fluids'• Both'leeches'and'the'earthworms'have'few'body'hairs''DThe'polychaetes,'have'many'hairs'• Most'polychaetes'are'marine'and'as'a'group'often'display'a'unusual'form'and'color'• They'often'have'one'or'more'pairs'of'eyes'and'tentacles.'Which'they'use'get'food'from'the'water'• 'One'of'the'largest'polychaetes'is'the'toothworm,'They'live'near'deep'sea'hydrothermal'vents.'They'don’t'have'functional'eyes'because'there'is'no'light'• But'they'do'have'symbiotic'chemoautotrophic'bacteria'that'provide'them'with'food.''Mollusks:'• Last'group'in'the'Lophotrochozoan'tree'• Highly'diverse,'more'than'100,000'members'of'species'• Bivalves'• Cephalopods'• Gastropods'• ChitonsD'• Many'body'plants'• The'ancestor'of'all'the'mollusks'were'probably'some'sort'of'segmented'worm,'but'the'development'of'the'three'part'mollusk'body'plan'lead'to'the'an'incredible'radiation'in'diversity'that'we'see'in'the'mollusks'• all'filter'feeders'• ex:'flame'scallop'• blue'ringed'octopusD'one'of'the'only'mollusks'that'is'dangerous'to'humans,'sharp'beak'that'will'deliever'a'poisionous'bite'• Banana'slugD'second'longest'slug'species'in'the'world.'It'gets'up'to'around'25cm,'nice'yellow'color,'nut'can'turn'multiple'flourence'colors'while'mating'• Have'been'around'for'a'very'long'time'ChitonsD'o Armored'little'pods''GastropodsD'o Slugs'and'snails''BivalvesD'o Clams,'mussels,'oysters'and'scallops.''CephalopodsD'o Octopuses''Three'party'body'plan:'o All'the'mollusks'derive'from'a'common'marine'ancestor'o This'ancestral'mollusk'had'this'three'part'body'plant'that'we'see'in'all'of'the'extant'modern'mollusk'groups'today:'o Muscular'foot'o Visceral'Mass'holds'the'organs'o Mantel'that'covers'the'internal'organs'of'the'visceral'mass'o Mollusks'organ'systems:'digestive'system,'reproduction,'and'excretory'system,'are'clustered'centrally'in'the'visceral'mass'in'the'body'of'the'mollusk'o The'footD'seen'in'all'mollusksD'used'for'locomotion'or'attachment'in'bivalves'and'chitons'and'also'for'food'capture'in'the'cephalopods.'o The'gastropods,'they'excrete'mucus'from'the'foot,'leaving'a'slug'trail.''o In'the'cephalopods,'the'foot'is'divided'into'tentacles,'used'for'direct'movement'and'capturing'prey.'This'indicates'the'foot'plays'multiple'parts.'o The'mantleD'thickened'sheet'of'skin'on'the'dorsal'part'of'the'mollusk'body.'It'covers'the'respiratory'organs.'For'most'mollusks,'it'will'secrete'a'shell.'The'shell'is'mostly'protective'as'the'mollusks'can'get'inside'it'shell'from'predators.'o Some'mollusks'like'the'cephalopods'and'slugs,'have'reduced'or'lost'this'shell.'''HeadsD'DSome'mollusks'groups'have'very'pronounced'heads'like'the'gastropods'and'cephalopods.''DThe'bivalves'have'no'or'very'tiny'heads'DThe'chitons'have'distinct'mouth'parts'at'a'interior'ends,'but'don’t'have'any'other'differentiation'of'a'head'DMost'mollusks'have'a'specialized'mouth'part'called'radula'DThe'radula'is'a'large'group'of'microscopic'teeth'arranged'in'rows'DMollusks'can'use'the'radula'to'scrape'algae''or'other'food'off'rocks'or'other'substrates'D'Some'gastropods'have'modified'radula'that'look'like'drills'to'bore'through'shells'of'prey'items.''DThe'bivalves'don’t'have'radula'because'they'are'headless.''SexD'o Most'mollusks'have'male'and'female'members'o Some'bivalves'and'gastropods'are'hermaphroditic'o Some'sea'slugs'and'oyster'have'separate'sexes'that'can'change'sex'multipul'times'in'the'course'of'a'single'season'o CrossDfertilization'is'the'standard'practice'in'mollusks'o Most'aquatic'mollusks'like'a'giant'clam'and'abalone,'they'have'external'fertilization,'preDzygotic'isolation'mechanism/'gametic'isolation'where'chemical'cues'that'typically'emanate'from'the'egg'that'fails'to'attract'sperm'or'can'prevent'fertilization,'effectively'blocking'the'incorrect'sperm'from'penetrating'the'egg''o .Gastropods'have'internal'fertilization,'this'along'with'mechanism'from'the'body'drying'out'where'some'of'the'main'adaptation'that'allowed'slugs'and'snails'to'colonize'land.'''Polyplacophora'aka'The'Chitons''o 1000'+'species'o Bodies'with'8'overlapping'dorsal'plates'o HerbivorousD'scraping'algae'off'rocks'with'radula'o Typically'live'in'shallow'water'o 'Small'oval'bodies''o Creep'along'on'broad'flat'foot'o While'most'chitons'use'external'fertilization,'few'use'internal'and'even'develop'embryos'internally''Gastropoda:'Snails'and'Slugs'o 40,000'species'o Most'slugs'and'snails'are'marine'like'Nudibranch'(sea'slug)'o Creep'along'on'muscular'foot'o The'nudibranch'make'it'clear'that'some'have'been'modified'for'free'swimming'as'well'o
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