echinodermata phylum echinodermata sea stars, sea urchins, sea cucumbers marine slow-moving or...
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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-: animal-plant; 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