ECHINODERMATA Phylum Echinodermata sea stars, sea urchins, sea cucumbers marine slow-moving or sessile.

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