Term
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Definition
Protochordata (Cephalochordata and Urochordata)
Vertebrata |
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Term
Chordata Ancestral Features
(6) |
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Definition
Bilateral Symmetry
Anterioposterior Axis
Well-developed Coelom
Tube within a tube body plan
Metamerism
Cephalization |
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Term
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Definition
Pharyngeal gill slits
Dorsal, hollow nerve cord |
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Term
| 5 Chordata Characteristics |
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Definition
Notochord
Dorsal Tubular Nerve Cord
Pharyngeal Pouches or Slits
Endostyle or Thyroid Gland
Postanal Tail |
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Term
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Definition
Rod-like, semi-rigid tissue enclosed in a sheath
Usually extends the length of body, ventral to central nervous system
Mainly serves to support and stiffen the body, providing attachment for muscles
Present at least at embryonic stage (in adults of protochordates and jawless vertebrates)
First part of the endoskeleton to appear in the embryo
Replaced by vertebrae in the "jawed" vertebrates |
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Term
Dorsal Tubular Nerve Cord
(3) |
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Definition
In most invertebrates: Nerve cord is solid and ventral to digestive tract
In chordates:
Single, tubular cord is dorsal to digestive tract
Produced in embryo by enfolding of ectodermal cells on the dorsal side of body |
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Term
Pharyngeal Pouches or Slits
(2) |
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Definition
Pharyngeal slits lead from pharyngeal cavity to the outside (Filter-feeding in aquatic chordates)
In vertebrates, pockets form and may not break through to outside (Evolution of jaws, internal gills, Eustachian tubes, middle ear cavities, tonsils, parathyroid glands) |
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Term
Endostyle of Thyroid Gland
(2) |
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Definition
On ventral wall of the pharynx, produces mucus to gather food particles
In vertebrates becomes the thyroid gland (regulates metabolism) |
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Term
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Definition
Evolved to improve propulsion in water
Efficiency increased in fishes with addition of fins
Became vestigial in humans (coccyx) |
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Term
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Definition
Adults are sessile
Larvae are free-swimming
All marine
Surrounded by a tough, nonliving cellulose tunic
Only larval form has all 5 chordate features |
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Term
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Definition
"sea squirts"
Solitary and colonial species
During metamorphosis notochord and tail disappear
Dorsal nerve cord is greatly reduced |
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Term
Ecteinascidia turbinata
(4) |
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Definition
Mangrove tunicate
Caribbean, Gulf of Mexico, and East Coast of US
Trabectedin anti-tumor drug
Undergoing clinical trials for the treatment of breast, prostate, and ovarian cancer |
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Term
Subphylum Cephalochordata
(4) |
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Definition
Lancelets or "amphioxus"
Genus Branchiostoma
All marine
Has all 5 chordate characteristics |
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Term
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Definition
Aka Clade Craniata
Chordates w/ bony or cartilaginous cranium
Hagfish have a cranium but lack vertebrae
Technically excluded from Vertebrata |
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Term
Early Vertebrate Characters
Differ from protochordates by:
(3) |
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Definition
Large size and activity style
Endoskeleton (notochord) and musculature permitting greater speed and mobility
Well-developed cranium, tripartite brain, and various sensory organs |
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Term
Early Vertebrate Characters
Bones
(4) |
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Definition
Endoskeleton initially composed of cartilage but later bone
Structural strength of bone is superior to cartilage
Bone's original function was probably mineral storage
Regulate phosphorus and calcium for active metabolism |
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Term
Early Vertebrate Characters
(6) |
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Definition
Digestive, respiratory, and circulatory systems modified to meet increased metabolic demand:
Muscular pharynx
Vascularized gills
Ingestion moved from ciliary to muscular action
Ventral 3 chambered heart
Erythrocytes containing hemoglobin |
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Term
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Definition
"shell-skinned"
The earliest vertebrates
Not natural evolutionary assemblage
Conveniently describes several groups of heavily armored extinct jawless fishes |
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