Chapter 34 Phylum Hemichordata- Acorn Worms

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Chapter 34 Phylum Hemichordata- Acorn Worms

• Have three body regions proboscis, collar, and
  trunk
• Have both a ventral and dorsal nerve cord
  anterior portion of dorsal is hollow
• Have pharyngeal gill slits
• Have ciliated larvae identical to echinoderms
• Have a hydrostatic skeleton
• Filter-feeders using their pharyngeal slits

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Hemichordata
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Hemichordata
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Hemichordata
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Hemichordata
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Hemichordata
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Chapter 34 Vertebrate Evolution and Diversity

• Characteristics of Chordata
• 1. Notochord
• 2. Dorsal hollow nerve cord
• 3. Pharyngeal Slits
• 4. Muscular Postanal Tail

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Notochord This is a longitudinal, flexible rod
of cartilage that is located between the gut and
the dorsal nerve cord. The notochord can last
into adulthood, but in most cases it is replaced
by the vertebral column. The spongy material in
between the vertebral bones is all that is left
of the notochord.
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Notochord
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Dorsal, Hollow Nerve Cord This is a tube that is
formed from a plate of ectoderm that is rolled up
into a tube. It is located dorsal to the
notochord, it lies above the gut and beneath a
single, hollow nerve cord. Due to its hollow
structure the dorsal nerve cord is considered
very unique. It will develop into the chordate's
central nervous system.
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Pharyngeal Gill Slits These structures are
openings of the upper digestive tube. During the
embryonic stage these slits connect the outside
to the pharynx. Early chordates used them to
filter feeding. Over time the slits became
modified to function in gas exchange.  
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Muscular Post anal Tail Most chordates have a
tail extending beyond the anus. In many aquatic
species the tail is equipped with skeletal and
muscular tissue for movement.  
Anus Tail
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Subphylum Urochordata
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Subphylum Urochordata-sea squirtstunicates
cellulose in outer covering
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Subphylum Urochordata
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Subphylum Urochordata
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Subphylum Urochordata
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Subphylum Cephalochordata lancelets
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Subphylum Cephalochordata lancelets

• Most like early chordates (but chordates did not
  descend from them)
• Marine filter feeders
• Feeble swimmers
• Muscles segments develop from blocks of mesoderm
  called somites that are arranged around each side
  of the notochord.

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Subphylum Cephalochordata lancelets
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Subphylum Cephalochordata lancelets
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Subphylum Cephalochordata lancelets
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Fossils of early vertebrates
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Subphylum Vertebrata

• Notochord develops into a cartilaginous or boney
  vertebral column that surrounds and protects the
  spinal cord
• Have a cranium or skull that surrounds and
  protects the brain
• Have a advanced closed circulatory system
• Cephalization increases dramatically

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Embryonic formation of the neural crest
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Class Myxini-Jawless fish-Hagfish-All marine No
limbs or appendages Cartilaginous skeleton no
vertebrae
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Class Myxini-Jawless fish-Hagfish
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Class Myxini-Jawless fish-Hagfish
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Class Myxini-Jawless fish-Hagfish
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Class Myxini-Jawless fish-Hagfish
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Class Cephalaspidomorphi-lamprey-Jawless fish
Cartilaginous skeleton No limbs or appendages
notochord has dorsal extensions that partially
enclose the nerve cord vertebrae
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Class Cephalaspidomorphi-lamprey
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Class Cephalaspidomorphi-lamprey
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Class Cephalaspidomorphi-lamprey
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Class Cephalaspidomorphi-lamprey
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Class Cephalaspidomorphi-lamprey
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Evolution of the Vertebrate Jaw
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Ostracoderms- armored but no jaws some were
active and had paired fins
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Ostracoderms
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Placoderms-first jaws

• Skeletal rods called gill arches of the most
  anterior pharyngeal gill slits became the jaw

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Placoderms
Placoderms
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Chondricthyes sharks and rays

• Completely cartilaginous skeleton
• Strong powerful swimmers
• Must swim constantly to produce water flow over
  gills due to no operculum
• Lateral line system that
  detects sound waves
• Oviparous
• Ovoviviparous
• Viviparous
• Cloaca

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Chondricthyes sharks and rays
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Chondricthyes sharks and rays
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Chondricthyes sharks and rays
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Osteichthyes-bony fish

• Operculum-bony covering over gill arches pulls
  water into mouth and over the gills
• Swim bladder- gives buoyancy regulates level in
  water evolved from crude lungs
• Bony fish evolved in freshwater first and
  developed crude lungs to supplement gills for gas
  exchange then when they returned to salt water,
  the opening to the lungs closed and they evolved
  into swim bladders
• Two chambered heart

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Ray-finned fishes
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Ray-finned fishes
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Ray-finned fishes
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Lobed-finned fishes
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Lobed-finned or lobed finnedfishes Coelacanths
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Lobed-finned fishes
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Lobed-finned fishes
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Lobed-finned fishes
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Osteichthyes- bony fish
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Osteichthyes-bony fish
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Amphibians

• Three chambered heart-
• External fertilization
• Embryo and larvae forms must have water
• Epidermis is permeable to water
• No claws on toes

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Amphibians
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Amphibians-salamander
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Amphibians-tree frog
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Young tadpole
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Tadpole to frog
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Amniote egg
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Reptiles

• Amniote egg-
• Scales composed of keratin-also protein in hair
  and feathers
• Three chambered with partial septum in ventricle
• Internal fertilization-
• Modern reptiles are ectotherms but many dinosaurs
  were endotherms

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Reptiles
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Care of eggs and young
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Reptiles
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Reptiles
Reptiles
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Reptiles
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Reptiles
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Reptiles
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Reptiles
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Reptiles
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Aves-birds

• Evolved from dinosaurs (reptiles)
• Modifications for flight-
• Internal fertilization with amniote egg
• Four-chambered heart
• Elastic air sacs connected to lungs for increased
  respiration and dissipation of heat

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Archaeopteryx
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Archaeopteryx
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Flightless dinosaur with protofeathers
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Caudipteryx flightless but with true feathers
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Aves
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Aves-Birds
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Aves-Birds
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Mammalian Characteristics

• Hair- composed of keratin
• Endothermic
• Mammary glands
• Four-chambered heart
• Diaphragm
• Internal fertilization
• Differentiated teeth

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Monotremes
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Monotremes
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Monotremes
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Monotremes-echidnas
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Monotremes
Monotremes-echidnas
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Monotremes-echidnas
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Monotremes-echidnas
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Marsupials
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Marsupials
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Marsupials
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Marsupials
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Prosimians-lemurs
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Hominid
Hominoid
Primates
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New world monkeys Old world monkeys
prehensile tail lack prehensile tail
nostrils open to the sides nostrils open
downward all arboreal some ground
dwelling
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Apes-Hominoids Not hominids
Gibbon
Orangutan
Chimpanzee
Gorilla
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Apes-Bonobo
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Hominids-bipedal-upright stance
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Lucy-Australopithecus afarensis early hominid
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Turkana boy1.7 million years oldbetween homo
habilis and homo erectus
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