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Anatomy-Chordates/Craniates
Exam 1
17
Anatomy
Undergraduate 3
02/24/2014

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Term
Phylum Chordata BIG FOUR
Definition
-notochord: flexible rod for support
-dorsal hollow nerve cord: hollow cord that is dorsal (above) the notochord
-pharyngeal slits: filter-feeding organs
-post anal tail: tail posterior to anus

-endostyle: area where the pharyngeal slits are located
-segmentation: repeated patterns in sharks
-bilateral symmetry
Term
notochord
Definition
-provides longitudinal support: core of cells and fluid encased in a tough sheath of fibrous tissue, stiffness is attributed to the turgidity of fluid-filled cells
-flexible laterally, but cannot change it's length
-stretches whole length of the animal

-anteriorly forms the floor of skull
-posteriorly supports the trunk and tail

-in vertebrates, the vertebrae develop after the notochord, and reinforces or replaces the notochord (some have both)
Term
pharyngeal slits/endostyle
Definition
pharyngeal slits: feeding mechanism
-bilateral apertures that connect the pharynx (anterior gut) to the outside
-used in suspension and filter-feeders along with the endostyle

-endostyle: has ciliated cells that secrete mucous that also trap food

-part of the respiratory system--gills reside in the slits anre involved in gas exchange
Term
dorsal hollow tube
Definition
-forms early in development, will turn into brain/vertebral column
-neurocoel: lumen for brain and spinal cord
-development: neurulation
Term
postanal tail
Definition
-tail that develops caudal to the anus or cloaca
-made of muscle, notochord, or vertebral bones, blood vessels and nerves
-some vertebrates: exists only in embryonic form
-function: important for movement and balance
Term
chordates
Definition
chordates are animals that have a notochord in the embryo stage (at least)
Term
craniates
Definition
craniates are chordates with a neurocranium
Term
vertebrates
Definition
vertebrates are chordates with a neurocranium and vertebrae
Term
vertebrate characteristics
Definition
-notochord
-dorsal hollow nerve cord
-pharyngeal slits and endostyle
-postanal tail

-sensory organs
-bilateral body plan/symmetry
-metamerism of muscles: repeated segments of structure
-endoskeleton: with vertebral column, cranium, and pharyngeal skeleton derived from neural crest
-multichambered heart
-coelum: open area in abdominal cavity
-muscular digestive tract: coordinated movement of food, increased breakdown of food with mechanical and chemical processing
-paired glomerular kidneys
-endocrine system: hormones
-separate sexes (most)
-two pairs of appendages (most)
Term
Von Baer's Law
Definition
All early craniate embryos exhibit a similar pattern of structure and development.

Common features develop early reflecting common ancestry.
Term
origin of craniata
Definition
-ancestral chordate of vertebrates were free swimming
-common ancestry of vertebrates and cephalochordata
-urochordata (in it's larval, free swimming form) may be the closest living relative to vertebrates
Term
earliest vertebrates
Definition
-changes in feeding apparatus lead to transitions to vertebrate evolution--increased movement
-prevertebrate organisms were filter feeders
-development of a jaw for hunting and capturing prey
-became pump filter feeders: development of a muscular pump and cartilaginous bars to support pharynx
-increased activity led to evolution of sensory organs, large brain, locomotion apparatus, metabolic machinery
-enlargement of brain for increased sensory information, movement, and feeding
-vertebral column for better support of muscle and increased locomotion
-respiratory system becomes more efficient
Term
urochordata
Definition
larvae stage
-pelagic or planktonic
-notochord
-endostyle
-dorsal hollow tuve
-pharyngeal slits
-postanal tail
-outer tunic of protein and polysaccharides with inner single layer of epidermis
-sensory vesicle for light detection
-otolith for gravity detection

adults
-marine, suspension feeders
-attached to rocks, stationary animals, can only feed on what goes by
-NO notochord or tail
-outer tunic is start of integumentary system
-incurrent siphon direct flow of water into pharynx and out of pharyngeal slits to outcurrent siphon
-rudimentary heart for early respiration
-coelom: pericardial cavity
-rudimentary brain for early neural organization(lack crania)
-hermaphroditic: sexual and asexual reproduction
Term
cephalochordata
Definition
-has brain; no head (expanded filter area at end)
-can swim and burrow into ground
-can move to get food
-notochord has a lot of musculature, exhibits metamerism (repeating segments)
-has 2-part skin
-filter feeder
-central nervous system
-no sensory organs
-respiration through skin
-metamerism in muscles
Term
ostracoderms
Definition
extinct armored fish; info via fossils

-swims well
-exoskeleton: bony scales, defined cranium
-cartilaginous endoskeleton
-small, slight paired fins
-no jaw: filter feeder
-sensory organs: eyes and naris
-pineal gland suggest brain
-mouth opening to oropharyngeal chamber with external gills
-external scales act as vertebral column: suggest notochord (primitive vertebrae)
-heterocercal (postanal) tail: dorsal-ventral flattening, bottom feeder
Term
hagfish
Definition
-has cranium with organized brain (but lacks jaw)
-sensory organs: sight, smell, electricity, balance, direction
-filter feeder
-scavengers rip pieces from dead animals with teeth--they clean up ocean corpses
-notochord (no vertebrae)
-flexible
-organized musculature for easy movement
-produces thick slime as a defense and can wrap self into knot
-multiple hearts
-nasopharynx and pharyngeal slits (gills)
-postanal tail
Term
lamprey
Definition
-has cranium with 3-part brain (but lacks jaw)
-spinal cord
-sensory organs: semicircular canals for balance, helps with swimming and directional information
-structure like a vertebrate heart
-pineal complex that calcifies with age
-organs are organized
-notochord surrounded by cartilage for support
-3 chamber heart
-endocrine system
-is a parasite
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