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Cards In This Set
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4 main characteristics of chordates
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- Notochord
- Muscular, post-anal tail
- Pharyngeal slits or clefts
- Dorsal, hollow nerve cord
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- ancestral vertebrate
- larvae have all 4 vertebrate characteristics, and retain them throughout adult hood
- larvae planktonic / adult burrows
- suspension feeders
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Cephalochordata = Lancelets
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- ancestral vertebrate
- larvae have all 4 chordate characteristics, lose many as progressing into adult hood
- larvae planktonic / adults sessile
- suspension feeders
- have only 9 hox genes instead of 13.
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Urochordata = Tunicate
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Chordates with define head
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Craniates
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Derived characteristics of Craniates
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- 2 clusters of hox genes
- gene families for transcription and signaling molecules
- neural crest (stem cell)
- More active and higher metabolic rates
- More complex muscularr system
- Heart with chambers - at least 2
- Red blood cells with hemoglobin
- Kidneys for excretion
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- least derived craniate lineage that still survives
- marine, bottom dweling scavangers
- skull made of cartilage
- lack jaws and vertebrae
- retain notochord into adult hood
- swim with segmented muscles
- small grain, eyes, ears, nasal opening
- mouths with keratin "teeth"
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Mixini = Hagfishes
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Vertebrates
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- craniates with backbones
- more complex nervous sytem and skeleton
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Derived characteristics of vertebrates
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- transcription factor genes: DLX family
- vertebrae enclosing spinal cord
- aquatic vertebrates - dorsals, ventral, anal fins stiffened by hard rays
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- oldest living lineage of vertebrates
- marine and freshwater, mostly parasitic
- larvae in FW streams resembling lancelet, suspension feeders
- most migrate to ocean as adults
- skeleton made of cartilage (no collagen)
- adult has notochord surrounded by cartilage pipe, surrounded by vertebrae related projections
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Petromyzontida = Lampreys
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Condonts
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- slender soft bodied vertebrates with eyes mineralized dental tissue
- hunters
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Evolution of bones in early vertebrates
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- mineralization associated wtih change in feeding from suspension to scavengers/hunters
- first mineralization - teeth
- second mineralization - skull
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Gnathostomes
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- vertebrates with jaws
- sharks, ray-finned fishes, lobe-fined fishes, amphibians, reptiles, birds, mammals
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Derived Characteristics of Gnathostomes
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- hinged jaws with teeth
- pharyngeal slits for gas exchange
- additional duplication of hox genes
- enlarged forebrain for sense of smell/vision
- lateral line system (aquatic vertebrates)
- ancestral: placoderms & acanthodians
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- sharks, rays, skates, etc. (~750 spp)
- "cartilage fish"
- marine, some are FW
- most are streamliined body
- fins: caudal, doral, pectoral/pelvic
- gas exchange through pharynx muscles to pump water over gills
- suspension feeders and predators: teeth, short digestive tracts, and spiral valve
- sharp vision, good olfaction, and ampullae of lorenzini (electric field detection)
- no ear
- internal fertilization
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Gnathostomes - Chondrichthyans
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Cartilage fish
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- skeleton primarily of cartilage with a little bit of calcium
- some bone in scales, base of teeth and some sharks vertebrae
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