Vertebrates Ch. 2: Origin of Chordates
Terms
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-fluid-filled internal body cavity
-organisms having this characteristic -
-coelom
-coelomates - "first mouth"--animals in which the mouth arises from the blastopore--includes molluscs, annelids, and arthropods
- protostomes
- "second mouth"--animals in which the anus arises from the blastopore--includes echinoderms, protochordates, and chordates
- deuterostomes
- dividing embryo cellds are offset from one another
- spiral cleavage
- dividing embryo cells are aligned
- radial cleavage
-
--process in which the ball of cells indents and grows inward
--opening of the indentation -
-gastrulation
-blastopore -
--the body cavity is formed from a solid sheet of mesodermal cells splitting
--the body cavity is formed from outpocketings of the gut that pinch off -
--schizocoely
--enterocoely - mechanical structure in which the outer wall encloses a fluid core
- hydrostatic organ
- remnant of the notochord in adult mammals with a full vertebral column--a small core of gel lying between vertebrae
- nucleus pulposus
- part of digestive tract immidiately posterior to the mouth
- pharynx
- blocks of muscle
- myomeres
- aquatic, free floating lifestyle, often planktonic
- pelagic
- life on marine substrate, adult protochordates consist mostly of this type
- benthic
- retention of larval characteristics in the adult (two terms)
- paedomorphosis (neoteny)
-
branch of protochordates with pharyngeal slits, dorsal nerve cord, but no notochord or postanal tail
--includes enteropneusta (acorn worms) and pterobranchia - hemichordates
- group that includes hemi-, uro-, and cephalo-chordates
- protochordates
- larvae of hemichordates
- tornaria
- sexual characteristic in which sperm and eggs are produced in the same gonad
- protandrous