Deuterostomes Flashcards
What are the three clades of Deuterostomes?
Hemichordata, Echinodermata, Chordata
What are Hemichordata?
acorn worms
What are Echinodermata?
sea urchins, sea stars
What are Chordata?
vertebrates and two lineages of invertebrate animals
What are distinguishing features of Hemichordata (acorn worms)?
threefold division of the body 1) proboscis, 2) collar 3)trunk with pharyngeal gill slits and a dorsal nerve cord
What does the muscular proboscis do in Hemichordates? for what purpose?
burrows into sand or mud; detritus feeders, extracting organic material from sand or mad
What features of hemichordates are shared with chordates?
branchial openings (gill slits)
stomochord in hemichordates resembles notochord
posses a dorsal nerve cord
What is the relationship between hemichordates and echinoderms?
they are sister taxa
What is a significant feature of Echinoderms? (they are deuterostomes…)
they secondarily evolved radial symmetry
larvae are bilaterally symmetrical
What are general characteristics of Echinoderms?
pentamerous (sets of 5) radial symmetry
poorly ganglionated; possess diffuse sensory structures
body wall contains endoskeleton of calcareous plates
water vascular system
What is tha water vascular system of echinoderms?
network of canals connected to podia (tube feet) extensions located on the oral surface.
What is the water vascular system important for in echinoderms?
locomotion, feeding, and gas exchange
What is reproduction like in echinoderms?
sexes are separate and fertilization is external
Why does molecular sequence data suggest that hemichordates are closer related to echinoderms? (over chordates)
larva look similar
What the 5 extant clades of Echinoderms?
Crinoidea
Asteroidea
Ophiuroidea
Echinoidea
Holothuroidea
What are Crinoidea features?
ancestral lineage
oral surface directed upwards; aboral surface is attached to the substrate by means of a bendable stalk
suspension feeders
What are Blastoids?
an extinct taxon of marine echinoderms
were stalked suspension feeders
What are Asteroidea?
sea stars
What are features of asteroidea?
typically 5 arms; merge with a central disc
mouth located in the center of oral surface directed downward
aboral surface with a madreporite opening of the water vascular system
What are the cleaning structures found on the aboral surface of sea stars?
pedicellariae (or jaws)
bonus: papulae are used for gaseous exchange
What are features of Echinoidea?
body is enclosed in shell or test
lack extended arms; fused to the test
body is usually covered with moveable spines
What are examples of Echinoidea?
sea urchins and sand dollars
What is Aristotle’s Lantern?
complex chewing apparatus used by sand dollars and sea urchins to feed by scraping algae off hard surfaces
What is an example of a holothuroidea?
Sea cucumbers
What are features of holothuroidea?
lack arms
oral-aboral axis greatly extended
tentacles collect food
endoskeleton is reduced to dermal ossicles scattered over the surface of the animal, making the soft bodied
