Origin and Evolution of Vertebrates

what do chordates have?

notochords, dorsal hollow nerve cord, pharyngeal slits, and post-anal tails

what are chordates comprised of?

1) cephalochordates (lancelets)

2) urochordates (tuncates -”sea squirts”)

3) vertebrates (everything w/ a backbone)

notochords

flexible rod between the digestive tube and nerve cord

dorsal hollow nerve cord

derived from ectoderm and neural tube formation that develops into the central nervous system

pharyngeal slits

openings into the pharynx that allows water to exit w/o entering digestive tract

post-anal tails

muscular tail extending beyond the anus

cephalochordates

-lancelets

-basal group of chordates

tunicates

-”sea squirts”

-swimming larva and sessile adults (most evident in larva)

vertebrates

-backbone/neural crest

what are vertebrates comprised of?

agnathans and gnathostomes

agnathans (vertebrates group)

-hagfish and lampreys

-jawless vertebrates

gnathostomes (vertebrates group)

-all jawed vertebrates

-includes chondrichthyans and osteichtyhans

chondrichthyans (gnathostomes within the vertebrates group)

-sharks and rays

-cartilaginous

osteichtyhans (gnathostomes within the vertebrates group)

-bony fishes

-opercula, scales (not all have them)

-swim bladders, ray or lobe finned

tetrapods

4 limbs

what are tetrapods comprised of?

-amphibians

-amniotes

-reptiles

-mammals

amphibians (tetrapods group)

-salamanders, frogs, caecilians

-life stages are aquatic and terrestrial

amniotes (tetrapods group)

-amniotic eggs

reptiles (tetrapods group)

-keratinized scales

-ectothermic (except birds)

-diapsids (except turtles)

what group are in reptiles? (tetrapods group)

-turtles=shelled

-crocodilians=crocs/alligators

-birds=flight adaptations, feathers, endothermic

-squamates=lizards/snakes

mammals (tetrapods group)

-milk producers, milk, mammary glands

what groups are in mammals? (tetrapods group)

-monotremes

-marsupials

-eutherians

monotremes (mammal group within tetrapods)

-egg born

-echidna

-platypus

marsupials (mammal group within tetrapods)

-pouch mammals

-kangaroo

-opossums

eutherians (mammal group within tetrapods)

placental