BIOL 2251 Echinoderms, Hemichordates, Chordates

Echinoderms and Chordates are part of this clade

Deuterostomia

Sessile

immobile

Oral (side)

Side with the mouth

Dermal gills

projections of the coelom of Asteroidea that serve in respiration and waste removal

Ambulacral groove

groove on oral side of Echinoderms extending from the mouth to the end of each arm that contain the tube feet

Eyespot

small light sensing organs located at the end of Echinoderm arms

Pentaradial symmetry is considered a/an [x] characteristic

derived

Aboral (side)

Side opposite the mouth

Number of extant species of Echinodermata

7,000

Most diverse classes of Echinodermata

Asteroida and Ophiuroidea

Water vascular system

Network of hydraulic canals branching into tube feet

Anatomy of tube foot

Ampulla and Podium

Echinoderms are usually

dioecious

Type of reproduction in Echinoderms

External

All Echinoderms have a [type] endoskeleton

Calcareous

Sea cucumbers have a [x] calcareous endoskeleton

Reduced

Pedicellariae

Small claw-shaped appendages that help clean Echinoderms’ body surface

Echinoderms have this type of gill

Dermal

Adult Echinoderms have this type of symmetry

Pentaradial

Madreporite

Calcareous opening on Echinoderms used to filter water through the water vascular system

Ring canal

Circular canal in Echinoderms filled with fluid used to distribute water to the radial canals

Stone canal

Carries water from the madreporite to the ring canal in Echinoderms

Radial canal

Canals in each arm extending from the ring canal in Echinoderms that distribute water to the tube feet

Ampulla

Squeezes water into the tube feet to stretch it out

Podium

End of a tube foot

Ossicles

Small calcareous structures that form the endoskeleton of echinoderms

What sets Hemichordata apart from Chordata

Gill slits and rudimentary notochord

Stomochord

Outpocketing from roof of gut, anterior to pharynx of Hemichordates

Hemichordates include

wormlike bottom-dwellers (acorn worms)

Echinoderms include

sea stars and urchins

Chordates include

the vertebrates and some invertebrate groups

Hox gene analysis reveals that Hemichordates are closely related to

echinoderms

Proboscis (Acorn worm)

Anterior end, used in movement and food particle transport

Collar (acorn worm)

ring-like structure between proboscis and trunk

Trunk (acorn worm)

Main body, behind collar

Acorn worm anatomy

Proboscis, collar, trunk

Gill pores

Gill slits, located on trunk of Hemichordates

Key characteristics of Chordates

Notochord, Dorsal hollow nerve cord, Pharyngeal slits or clefts, Muscular post-anal tail, Endostyle

Endostyle

Precursor to thyroid glands, associated with the pharynx in Chordates

Notochord

rod-like, semirigid tissue enclosed in a sheath usually extending length of body, just ventral to central nervous system

Subphylum Cephalochordata

Lancelets named for blade-like shape, marine suspension feeders, retain chordate body plan as adults

Subphylum Urochordata

Tunicates, most resemble chordates as larvae

Urochordata adults

Draw in water through an incurrent siphon and filter food particles, can shoot water through excurrent siphon

Tunicates are more closely related to [x] than to [x]

other chordates, lancelets

Earliest vertebrates were

small, mostly soft-bodied from early Cambrian

Fossil record of earliest vertebrates shows

paired eyes, complex swimming muscles, prominent gills, and rudimentary vertebrae

Ostracoderms

Jawless fishes, armored with bone in dermis, no paired fins, late Cambrian and Devonian. Heterostracans and Osteostracans

Osteostracans

Ostracoderms, coexisted with Heterostracans, Paired fins to stabilize movement, jawless, toothless, well-armored head

Heterostracans

Early ostracoderms, awkward design, filtered particles from ocean floor, extinct near end of Devonian

Conodonts

Among earliest vertebrates, mineralized skeletal elements in mouth and pharynx

Mineralization first appeared with

mouth parts

Gnathostomes

All living and extinct jawed vertebrates

Placoderms

Among the first gnathostomes, armored fish covered with diamond-shaped scales or large plates of bones, all extinct by Devonian

Postanal tail

extension of the notochord and nerve chord extending beyond anus

“Perfect” Chordates

retains all key characteristics into adulthood

Ascidian

Sea squirts, or Tunicates

What did Placoderms give us

Jaws

Hydrostatic skeleton

Fluid filled cavity acting as a shock absorber and allowing for movement

All jawed fishes and tetrapods constitute a

Monophyletic group (share a common ancestor)

Gnathostomes resulted from

first 2 pairs of cartilaginous gill arches