Download ECHINODERMATA

ECHINODERMATA
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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
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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
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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
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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
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very modified for flight
furcula (wishbone), feathers
Archaeopteryx; discovered in 1861
Fig. 34.29
BIRDS
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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
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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
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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
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many factors, including:
habitat loss (agriculture, development)
introduction of non-native species
global climate change
2 root causes
– overpopulation
– overconsumption