Lecture 17

Question 1

Know the basic features of enchinoderm anatomy: Pentameral symmetry,
calcite ossicles, water vascular system and ambulacral areas, oral and aboral
surface. Know that the mouth is always on the oral surface, but the position
of the anus varies.

Answer 1

from ppt

Question 2

Asteroidea (sea stars): Where is the anus located? What is the madreporite,
and where is it located? What are tube feet, and where are they located?

Answer 2

ppt

Question 3

Ophiuroidea (brittle stars): Be able to recognize one.

Answer 3

ppt

Question 4

Regular echinoids (sea urchins): What is the opening for the mouth called?
Where is it located? What is the opening for the anus called and where is it? If
I show you a picture of the madreporite and genital plates, know which are
which. What are gonopores for? What do urchins do for a living?

Answer 4

a. mouth opening: peristome and located on the underside (oral surface)
b. anus opening: periproct and located on top side (aboral surface)
c.gonopores are located on genital plates and are the openings through which gametes are released into water for external fertilization.
d. sea urchins are grazers, they feed on algae and control algae growth and maintaining balance to marine ecosystem.

Question 5

Irregular echinoids (sand dollars and sea biscuits): How is the symmetry,
location of the periproct, and location of the madreporite different than in
sea urchins? How is the lifestyle of sand dollars different from sea urchins?

Answer 5

a. periproct is often shifted toward the rear of the aboral side and the madreporite is usually on the oral surface
b. They ingest grains of sand and detritus along with microorganisms and organic matter. They process the sand, extracting food, and then expel the cleaned sand grains. Sea urchins often move around openly on rocky or reef surfaces using their spines. Sand dollars, however, are usually found partially buried in sandy or muddy substrates in shallower waters.

Question 6

Stalked enchinoderms (crinoids, cystoids, blastoids): Be able to distinguish
different groups, and to be able to identify the theca/calyx and stem. When
were different groups of stalked enchinoderms most common, and when did
cystoids and blastoids go extinct? Which group still survives today?

Answer 6

-crinoids: have a cup shaped body known as theca/calyx and its supported by a jointed stem that can attach to substrate. first appeared in Ordovician period and are still alive today. abundant in Paleozoic
-cystoids: is similar to crinoids but have an more globular theca, fewer arms and body is covered w tessellated pattern. most common from ordovician to devonian period and went extinct by the end of devonian.
-blastoids: theca is pear shaped theca and lack arms. appeared in Ordovician but most common in carboniferous, they went extinct at the end of the Permian period.