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ECHINODERMATA • • • • Phylum Echinodermata sea stars, sea urchins, sea cucumbers marine slow-moving or sessile ECHINODERMATA • deuterostome developmental characters • symmetry: secondarily radially symmetrical • larval stage: bilateral symmetry; ancestral condition • adult stage: radial symmetry; derived condition • not homologous with that in Cnidaria • homoplasy ECHINODERMATA • • • • • • • • aboral-oral body orientation oral: side with a mouth aboral: side opposite the mouth water vascular system derived from coelom, including tube feet endoskeleton derived from mesoderm ossicles: crystals of calcium carbonate increase body size without shedding dioecious ECHINODERMATA • reduced circulatory, excretory, respiratory systems • diffusion important • well-developed nervous, muscle, digestive systems • uncentralized nervous system (no cephalization); nerve rings & cords • great regenerative ability • will examine 2 Classes ASTEROIDEA • Class Asteroidea (aster-: star; sea stars); Fig. 33.39 ASTEROIDEA • central disk with gradually tapering arms • madreporite on aboral surface; opening into water vascular system • tube feet with suckers and ampullae • ambulacral groove • muscles contract around ampullae, moves tube feet ASTEROIDEA • • • • • eats bivalves everts stomach between shell releases digestive enzymes pumps out predigested body reproductive system: gonads within each arm HOLOTHUROIDEA • Class Holothuroidea (holothur-: animalplant; sea cucumbers) HOLOTHUROIDEA • tube feet • tentacles: modified tube feet around mouth • “under pressure, disembowels itself” • “breathes thru anus” • “entertains visitors in its anus” • “projects its anal plumbing in your face” HOLOTHUROIDEA • respiratory trees: coming from anus • pearlfish; elongate, thin; feeds at night • day: forces way into anus, up the respiratory trees • advantage to fish: protection?; food? • disturbed: shoots out of anus Cuvierian tubules; sticky web HOLOTHUROIDEA • evisceration: sides split open, throws out most internal organs • lost parts later regenerate • probably not for defense • adaptation to environmental stress • lowers energetic demand CHORDATA • Phylum Chordata • deuterostome developmental characters • 3 subphyla – 2 invertebrate: marine – 1 vertebrate: marine, freshwater, terrestrial, aerial • 4 key chordate characters; Fig. 34.3 CHORDATA • 1) notochord: dorsal, longitudinal, laterally flexible rod • noto = back; chord = string of a musical instrument • between digestive tube and nerve cord • energy-saving for swimming • localizes muscle contractions among segments • 2) dorsal, hollow nerve cord • cells of ectodermal plate roll together to form neural tube; Fig. 34.7 CHORDATA • becomes central nervous system (brain, spinal cord) • stimulates dorsal swimming muscles • 3) pharyngeal slits • original function: trap food particles for filter feeding • later: respiration as pharyngeal gill slits CHORDATA • • • • • • 4) muscular, post-anal tail propulsive force in swimming ancestral chordate aquatic, active some segmentation seen in body muscles; vertebral column 3 subphyla; Fig. 34.2 CHORDATA • Subphylum Cephalochordata • lancelets; Fig. 34.4 CEPHALOCHORDATA • filter-feeder with fish-like swimming • adult with all 4 chordate characters • endostyle: secretes mucus onto pharynx • becomes thyroid gland in vertebrates • functional shift; comparative anatomy CHORDATA • Subphylum Urochordata • tunicates; Fig. 34.5 UROCHORDATA • uro: tailed (tadpole-like larva) • has all 4 characters • adult: marine, sessile, filter feeder – endostyle • produce anti-cancer chemicals • regenerative medicine • sister group of Subphylum Vertebrata VERTEBRATA • Subphylum Vertebrata (vertebrates) • all 4 chordate characters, but with modification, reduction or loss • comparative embryology • human embryo shows all 4 chordate characters; Fig. 22.18 VERTEBRATES • vertebrate trends in the 4 chordate characters • notochord: becomes core around which vertebral column forms • becomes mostly replaced by cartilage and/or bone • dorsal, hollow nerve cord becomes augmented by neural crest; Fig. 34.7 VERTEBRATES • neural crest: embryonic cells near dorsal margins of neural tube • unique to vertebrates • develop into cranium (braincase), skin pigment cells, teeth, sense organs, etc. • pharyngeal slits took on another function: gills for respiration • first vertebrates jawless • skeletal rods support pharyngeal gill slits; Fig. 34.13 VERTEBRATA • two pairs of anterior skeletal rods modified into jaws • capabilities beyond filter feeding • muscular, post-anal tail retained • diversity within vertebrates; Fig. 34.2 • cartilaginous fish; sharks, rays – endoskeleton of cartilage VERTEBRATA • ray-finned fish; most speciose – endoskeleton of bone VERTEBRATA • lobe-finned fishes (= coelacanths): sister group of lungfish + tetrapods; Fig. 34.18, 34.20 VERTEBRATA • 3 tetrapod groups (land vertebrates); 4 feet & legs; Fig. 34.20 • amphibians • reptiles (includes birds) • mammals AMPHIBIA • amphibians: tied to water because eggs need constant moisture REPTILIA • fossil groups such as dinosaurs; Fig. 34.24 • living groups: lizards, snakes, turtles, crocodiles REPTILIA • freedom from water/moist habitats • amniotic egg; Fig. 34.25 • functionally analogous to seeds of land plants • internal moisture, nutrients • amniotes (reptiles, birds, mammals); Fig. 34.24 BIRDS • birds; some group as a reptile • one of 3 vertebrate flying groups (Fig. 34.24) – pterosaurs (not a dinosaur) – bats • • • • very modified for flight furcula (wishbone), feathers Archaeopteryx; discovered in 1861 Fig. 34.29 BIRDS • • • • • • evolved from reptiles; what group? theropod dinosaurs Velociraptor has a furcula other small species with feathers Microraptor fossil what was original function of feathers? – thermoregulation? – display? MAMMALIA • Class Mammalia; Fig. 34.35 • montremes, marsupials, eutherians MAMMALS • hair; mammary glands (milk) • incus, malleus middle ear bones; Fig. 34.31 • shift from quadrate-articular jaw joint to squamosal-dentary jaw joint • functional shift from jaw joint to improved hearing • quadrate → incus • articular → malleus MAMMALS • • • • • monotremes: egg-laying mammals reveals ancestry from amniotes marsupials: pouch (marsupium) eutherians: placenta direct connection between developing embryo and mother PRIMATES • primates; Fig. 34.37 PRIMATES • • • • arboreal (tree-dwelling); leaping stereoscopic (3-D) vision grasping hand & foot enlarged brain HOMININS • hominins (many fossil species, Homo sapiens) • bipedal (walk upright), fully opposable thumb; Fig. 34.41 HOMININS • which is the sister taxon to hominins (includes Homo sapiens)? • several ape species were candidates SISTER GROUP • chimpanzee + bonobo clade FUTURE • future of biodiversity linked to future of humans • human-caused mass extinction FUTURE • • • • • many factors, including: habitat loss (agriculture, development) introduction of non-native species global climate change 2 root causes – overpopulation – overconsumption