Biodiversity and Conservation Chapters 14 & 15, Echinodermata and Hemichordata

7,000

Number of described Echinodermata species

Asteroidea

Class of Echinoderms that includes sea stars

Slow moving or sessile

Most common movement type in echinoderms

Water vascular system

A network of hydrolic canals branching into tube feet 

Key characteristics of echinoderms

Calcareous endoskeleton, pedicellariae, dermal gills, and pentaradial symmetry

Carlcareous endoskeleton

Skeleton type of echinoderms in which there are large plates or small ossicles of calcified material

Pedicellarie

External component of echinoderms that help to cleap the body surface

Pentaradial symmetry

Symmetry in five parts; found in adult echinoderms

Madreporite

Opening of the water vascular system in sea stars

Stone canal

Connection between the madreporite and the ring canal in sea stars

Radial canals

Canals that connect the ring canal to the legs of the sea star

Tube foot

Made up of the ampulla and podium; functions for locomotion, sensing, and gas exchange

Sea star digestion

Digestion process in which the organism inverts its stomach outside its body in order to liquefy prey

Phylum Hemichordata

Phylum that was previously considered a subpyhlum of chordates; made up of worm-like bottom dwellers, who live in shallow waters and are sedentary or sessile

Notochord

Rod-like, semirigid tissue enclosed withing a sheath, made of a primitive type of collagen that extends the length of the body ventral to the central nervous system; origin of the name “chordata”

Characteristics of chordates

Notochord, hollow dorsal nerve chord, pharyngeal slits, post-anal tail, and Endostyle

Endostyle

Usually associated with the pharyngeal slits

Subphylum Cephalochordata

Only group of chordates to retain all derived characteristics in the adult form

Lancelets

Marine suspension feeders in subphylum cephalochordata that live in the substrate

Subphylum Urochordata

Subphylum of chordates that includes tunicates

Tunicates

Sedentary chordates that draw in water through incurrent siphons, and only resemble chordates in the larval stage

Ostracoderms

Group of chordates that were jawless fish with bone in their dermis

Aspidin

Primitive bone-like tissue used in ostracoderms that was made up of enameloid or dentine

Heterostracans

Early group of ostracoderms that were filter feeders and went extinct near the end of the Devonian period

Osteostracans

Group of ostracoderms that developed early systems of paired fins and had a jawless, toothless mouth with an armored head and head shield

Conodonts

Among the earliest vertebrates in the fossil record, and had mineralization internally in their mouth and pharynx

Gnathostomes

Term for all living and extinct jawed vertebrates

Jaw origin

Body part that originated by the modification of the first two pairs of cartilaginous gill arches

Placoderms

Group that was one of the first jawed vertebrates, and were an armored fish with large plates of bones; went extinct by the end of the Devonian period