Deuterostomes PART TWO

what is the current eon?

phanerozoic eon

when did hard-bodies invertebrates first appear?

cambrian eon, around 540 mya

what is the burgress shale

best record of cambrian fossils and allowed for the appearance of lots of new phyla in a very short time

what are the two lineages of non-vertebrate chordates?

tunicates (sea squirts), cephalochordates (lancelets, amphioxus)

key chordate features

notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail

what is the notochord (chordate feature)?

stiff but flexible cartilaginous rod

what is the dorsal hollow nerve cord (chordate feature)?

acts as ‘brain’ - mahy show anterior expansion

what is the post-anal tail (chordate feature)?

muscular, extends beyond tail

three classes of tunicates

ascidiacea (sea squirts), appendicularia (larvaceans), thaliacea (salps)

three exant genera of cephalochordates?

asymmentron (2 sps), branchiostoma (20-25 sps), epigonichthys (6 sps)

key features of non-vertebrate chordates

v-shaped segmented muscules, notochord, dorsal hollow nerve chord, pharyngeal slits, post-anal tail

non-vertebrate chordate feeding technique

passive filter-feeding lifestyle, low metabolic rates

two major exant lineages of vertebrates?

agnatha (jawless fish), gnathostomes (jawed vertebrates)

what are placodes? (vertebrate innovation)

ectodermal thickenings that form in particular regions of the developing head

how many cranial nerves do humans have

12 pairs

olfactory placode function?

smell

trigeminal placode function?

touch, temperature, pain

otic placode function?

sound, balance

epibranchail placode function?

taste buds, tongue, heart and guts

what is the neural crest? (vertebrate innovation)

specialised migratory cells that contribute to a diversity of cell types

what three skeletons do most vertebrates have?

craniofacial, axial, appendicular - mineralised tissues (cartilage, bones, teeth)

what is the craniofacial skeletons?

neural crest-derived

what is the axial skeletons?

vertebrae, ribs - formed from somites

what is the appendicular skeletons?

limbs - formed from lateral plate mesoderm

what types of fins do vertebrates have ?

median fins (along body midline) and paired fins (on left and right)

types of median fins?

dorsal, caudal, adipose, anal fins

types of paired fins?

pectoral, pelvic fins

vertebrate key features

placodes, neural crest, tripartite brain, mineralised tissues, paired fins, w-shaped muscles

vertebrate feeding stratergies?

active, swimming predator with a higher metabolic rate