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40 Cards in this Set
- Front
- Back
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Mechanisms of evolution
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high reproductive potential
competition for the declining resources survival of the few- natural selection |
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homology
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2 or more features that share a common ancestry
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analogy
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features with a similar function
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radial symmetry
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a boy is laid out equally from a central axis
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frontal plane
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divides a bilateral body into dorsal and ventral, where as a transverse plane divides into top and bottom
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hydrostatic skeleton
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a fluid-filled cavity enclosed by a membrane and muscular coat
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3 groups of living chordates
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vertebrates
cephalochordates urochordates |
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coelom
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fluid-filled internal body cavity
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schizocoelom
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solid mass of mesodermal cells split to form the body cavity within them
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enterocoelom
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mesoderm arises as outpocketings of the gut that pinch off to form body cavity (deuterostomes)
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protostomes
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blastopore = mouth
spiral cleavage schizocoelic coelom ectodermal skeleton |
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5 fundamental features of Chordates
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notochord
dorsal hollow nerve cord endostyle/thyroid gland pharyngeal slits post-anal tail |
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notochord
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lies dorsal to coelom but beneath and parallel to the CNS mechanical propertes
can be flexed laterally side to side but cannot be collapsed (core of cells and fluid encased in tough sheath) |
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endostyle
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a glandular groove in the floor of the pharynx, involved in filler feeding
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dorsal & tubular nerve cord
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neural plate folds or rolls up and sinks inward from the surface as a tube to take up residence...just above the notochord
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myomere
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blocks of muscle & segmentation in chordates
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protochordates
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primitive chordates
sessile & burrowing both dioceous and monoceous |
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hemichordate
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burrowing forms and sessile forms
system: nephridium, pulsatile vesicle, muscle and connective tissue lining, probiscis duct, podousla w/specialized blood vessels |
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enteropheusta
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acorn worms: marine animals
deep/shallow waters 3 regions : probiscis, collar, trunk live in mucous lined burrows |
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glomerulus (hemichordates)
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podousla w/specialized blood vessels
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pulsatile vesicle (hemichordates)
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contractile tissue, or heart vessicle
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nephridium (hemichordates)
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an excretory organ
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pterobranchia
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2 genera: sessile pterobranch
suspension feeding live in secreted tubes small and colonial zooid |
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zooid
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each individual contributes to the group
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Hemichordate affinities to Echinoderms
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marine
unsegmented pentaradial symmetry endoskeleton water vascular system no head/brain present nervous system: radial nerves from central nerve ring |
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cephalochordates
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ex: lancelets, amphioxus
pharyngeal slits, etc. suspension feeding: oral hood, buccal cirri (prevent entrance of large particles), wheel organ, Hatscheks pit/groove velum, atriopore |
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velum
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partial diaphragm, short sensory tentacles
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Hatscheks pit/groove
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like vertebrate pituatary glands
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cephalochordates: circulatory system
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paired anterior and posterior cardinal veins + the hepatic vein = swollen sinus venosus --> the endostylar artery (ventral aorta) --> the visceral, skeletal, coelomic vessels
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larval amphioxus
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planktonic
assymetrical in head and pharyns pharyngeal slits only on left side of the body |
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specialized notochord of amphoixus (cephalochordate)
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notocord sheath
plates of slowly contracting muscles cytoplasmic extensions of these plates synapse w/the dorsal nerve cord fluid-filled spaces separate muscle cells |
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urochordata
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5 chordate characteristics
suspension feeding marine tunic-flexible outer body cover ex: ascidiacea (sea squirts) |
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Sea Squirts (Ascidiacea)
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marine animals, brightly colored, solitary/colonial
adults are sessile, larvae planktonic sensory vesicle: the ocellus and the otolith neural crest: pigment cells the CNS has 3 subdivisions |
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3 subdivisions of the CNS (Ascidiacea)
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visceral ganglion
dorsal nerve cord sensory vesice (ocellus and otolith) |
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adult solitary ascidian
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tunic
atrium branchial basket viscera incurrent and excurrent siphons oral tentacles the heart = single layer of muscle |
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Larvacea (appendicuularia)
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monoecious
suspension feeding (gelatinous matrix) protandrous (sperm and eggs, same gonad) House building, reverse flow clears clogged filters |
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Thaliacea
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free living, pelagic
derivative of the adult ascidian |
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Chordate Origin hypotheses
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1. chordates from Annelids/ Arthropods (a/a on its back = basic chordate body)
2. chordates from echinoderms (both deuterostomes, share embryonic similarites) |
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prochordate to chordate
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the dorsoventral inversion of chordates occured w/in the deuterostomes
dorso/ventral axis changed (reversed) |
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paedomorphisis
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retention of some larval traits in the adult
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