Chordates (Phylum Chordata)

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Chordates (Phylum Chordata) Tunicates/Sea
squirts (Urochordata) Lancelets
(Cephalochordata) Vertebrates (Craniata -
formerly vertebrata)
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A. Characteristics 1. Notochord a.
slender rod - provides axial support 2.
Pharyngeal gill slits a. feeding in
primitive chordates, became gills 3. Dorsal
Hollow Nerve Cord (DHNC) a. fluid filled
central canal above notochord b. solid and
ventral in other invertebrates 4. Postanal Tail
Dorsal, Hollow Nerve Cord
Notochord
Pharyngeal Slits
Postanal Tail
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B. Tunicates (Subphylum Urochordata) 1. Sessile
Marine animals 2. 2 life stages a. larval
stage has chordate traits
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C. The lancelets (Subphylum Cephalochordata) 1.
small (lt5cm), fusiform, Marine organisms 2.
Paedomorphosis a. juvenile morph is
retained in reproductive adult b. retained
larval form of Urochordates in reproductive adults
Urochordate Larva
Lancelet Adult
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C. Vertebrates 1. Subphylum Craniata a.
formerly Vertebrata
Phylogeny from
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2. Vertebral Column a. Centrum - Bony
vertebral column i. replaces notochord
a. Neural Arch - encircles nerve cord - forms
neural canal - some vertebrates lack vertebrae
i. Hagfish-strengthend notochord 3. Cranium
a. surrounds anterior brain - bone or cartilage
Vertebra
Cranium
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4. Jawless Fishes (Superclass Agnatha) a.
Hagfish (Class Myxini) - conatin most
primitive characters - No vertebrae b.
Lampreys (Class Cephalaspidomorphi) -
Cartilagenous vertebral plates - Parasitic
on other vertebrates
Hagfish
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5. Jawed Fishes (Superclass Gnathostoma) a.
Jaws b. 2 sets of paired fins (Yaw, Pitch, roll)
Modern Fishes
Jawless Ancestors
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c. Cartilaginous fishes (Class Chondrichtyes) -
Sharks and Rays - Cartilage skeleton -
Multiple gill slits - Oil filled liver for
buoyancy i. Also hydrodynamic lift
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- Reproduction i. Oviparous - lay eggs ii.
Ovoviviparous - retain eggs internally until
hatching iii. Viviparous - live bearing,
nourishment from mother
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d. Bony Fishes (Class Osteichthyes) - Operculum
- bony structure covering gills - swim bladder
i. burp/gulp - connected to stomach -
primitive ii. gas exchange - connected to
blood vessels - derived
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- Ray-finned fishes (Actinopterygii) i.
Extremely diverse ii. most of the fishes you
know
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- Lobe-finned fishes (Sarcopterygii) i.
Lungfish Live in shallow, fresh water
Rely on lungs during dry season ii.
Coelocanth Bottom dweller (off coast of
Africa)
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e. Transition to Land
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f. Amphibians (Class Amphibia) - Salamanders,
toads, frogs, caecillians -Moist skin i.
adapted for cutaneous respiration - Oviparous
i. Undergo metamorphosis
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g. Amniotes - Have amniotic egg i. shell
that retains water - Can lay eggs in dry
environments
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h. Turtles (Anapsids) - Shell - no temporal
fenestra (anapsid) - oviparous
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i. Snakes and Lizards (Lepidosaurs) - Diapsid
skull i. two fenestra (holes in temple)
- Cranial kinesis (skull flexion) - scales
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j. Archosaurs - Crocodilians, Pterosaurs,
Dinosaurs, Birds - Diapsid skull - Antorbital
fenestra
Archosaurs
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k. Birds (Class Aves)
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- Feathers i. Rachis and Barbs
Rachis
Barbs
Rachis
Barb
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- Bones (hollow, cross struts) - Keeled Sternum -
Furcula (Wish bone) - Homeotherm i. constant
body temperature ii. endothermy
Furcula
Bird in flight
Keeled Sternum
Flightless birds
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- Bill i. No teeth ii. Light keratin beak
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6. Class Mammalia - Mammals
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1. Synapsid skull a. 1 temporal opening
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2. Hair - keratinized filaments
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3. Mammary glands a. produce milk to nourish
young b. derived from sweat glands
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- Heterodont dentition i. incisors - snipping
ii. canines - tearing, grasping iii. cheek
teeth - premolars - crunching - molars grinding
or slicing
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- Limb position i. ventral - positioned under
body - differs from lateral position in
ancestors - Endothermy/Homeothermy
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(No Transcript)
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- Monotremes - oviparous
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- Marsupials i. primitive placenta ii.
altricial young
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- Eutherian mammals i. derived/advanced
placenta ii. precocial young iii. most
familiar mammals