Exam 1 Chapter 2: Protochordates and Chordate Origins Flashcards
Define protostome development
- spiral cleavage, blastopore becomes mouth
- mesoderm origin in mesentoblasts
Define deuterostome development
- Radial Cleavage, blastopore becomes anus
- origin of mesoderm from blastomeres
Name the five basic chordates characteristics
- notochord, pharyngeal slits, endostyle/thyroid, Dorsal hollow nerve cord, postanal tail
Notochord
chord bendable(so laterally flexible), but not compressible (resists shortening in length); lies along the path of the dorsal hollow nerve cord
o Without a notochord, lateral muscle contraction telescopes the body uselessly
o Notochord prevents collapse of the body - muscle contractions on alternating sides flex the body
Pharyngeal Slits
o Start in pouch form (pouch on one side, slide on other)
o Contributes to filter feeding, through front and items sucked out through slits
Endostyle/thryoid
- endostyle provides filter feeding
- thryoid regulates metabolism, effects bodily organs
Dorsal hollow nerve cord
on top of notochord, provides skeletal support and movement
Postanal tail
source of locomotion
In deuterostomes, which of the following groups are informally called “protochordates”?
o Hemichordata
o Chordates (Cephalochordata)
o Urochordata
o Vertebrata
Groups in Ambulacraria
- hemichordata, echinodermata
Echinodermata
o Echinoderms (“spiny-skins”) are named for the spines or spikes observed in many species
o All echinoderms are marine animals
o Bilateral as young, become radial later in development
o Deuterostomes, makes them closer to chordates
Examples: Seastars, starfish, sea urchins, anemones
Hemichordata
Enteropneusta and Pterobranchia
Enteropneusta
- acorn worms
o One chordate trait: pharyngeal slits
Pterobranchia
pterobranchs: tiny, attaches to surfaces, secrete carbohydrate tube(s)
One chordate trait: pharyngeal slits
Groups in Chordata
- Cephalochordata, Urochordata
