Phylum Echinoderms Flashcards
What does Echinodermata mean
spiny skin-endoskeleton of dermal ossicels with projecting spines
what are humans more closely related to than any other invertebrate group
echinoderms
what type of symmetry do adult echinoderms have
radial symmetry
what type of symmetry to larval echinoderms have
bilateral symmetry
what is secondary radial symmetery
radial symmetry is secondarily derived, it is an advanced feature, not primitive one
How well developed is cephalization in echinoderms, and
how well developed is their nervous system?
cephalization is reduced or absent in this group
nervous system is decentralized – no brain
most feed on small organic particles or algae, or small
prey
some (sea stars and sea urchins) are efficient predators
most are active, mobile animals
function of water vascular system in echinoderms
respiration, locomotion, and excretion
explain water flow through echinoderms
stone canal>ring canal>radical canal>lateral canal>ampulla>tube feet
How does coelom function in this phylum
circulation, respiration and excretion
fluid circulated by cilia on the peritoneum lining the eucoleom
how does this phylum excrete and do gas exchange
excretion and gas exchange via papulae and tube feet which project out between ossicles
What is endoskeleton consist of
dermal ossicles: little plates under skin, jointed by connective tissue, muscle
some project outward as spines
what are pedicellariae
Small pincers extending from skin (only sea stars and
urchins)
Clean skin of debris, protect papulae, may aid in food
capture in some
In sea stars and urchins only
What is most common type of repro (dioecious or monoecious)
mostly dioecious
what is autotomy and how does it happen
where organism regenerates itself
all it needs is one arm and a 1/5th of oral disc
what is in class crinoidea
sea lilies and feather stars
explain sea lilies and feather stars
Both start out attached to the substrate
much of life sessile
Arms are tentacle-like with leathery skin and small
branches and mucus for trapping and eating
suspended phytoplankton
What group first introduces secondary radial symmetry
echinoderms which was adaptated for feeding
example of class asteroidea
starfish
how do starfish feed
predators with eversible stomach; insert cardiac stomach into open bivalve shell to digest and absorb soft parts
how are tube feet used in feeding
used to grip bivalve shells so shells can be pulled apart
what is in class echinoidea
sea urchin
what is unique about oral surface in sea urchins
oral surfaces has expanded around to the aboral side
fused dermal ossicles form a rigid test with long moveable spines tube feet and pedicellariae
in sea urchin what is Aristotle’s lantern
complex 5 part jaw structure
used to graze; feed on algae
what is also in class echinoidea
sand dollar
what does sand dollar have and do
very small spines used to burrow just below
the sand
rigid test, with tube feet, and pedicellariae
Organic particles settle on aboral surface,
and cilia move them down to mouth
HAVE TEETH
what is largest class of echinoderms
class ophiuroidea
whats in class ophiuridea and where are they abundant
brittle stars and basket stars
abundant in oceans, often covering sea bottom
what type of feeding so class Ophiuroidea do
detritivores; feed on decaying matter and plankton via movable jaw
how does class Ophiuroidea have locomotion
moveable arms
unique features of ophiuroidea
no intestine or anus (incomplete digestive system)
no pedicellariae or papullae
autotomy is best in this class
what is in class Holothuroidea
sea cucubmbers
what is pedicellariae
small wrench or claw shaped appendage with moveable jaw
what is papillae (Papula)
dermal branchia or skin gills
how do Holothuroidea differ from echinoderms
greatly elongated on oral-aboral axis
ossicles reduced so body is soft
arrangement of tube feet modified for crawling
how do holothurdoidea feed and defend themselves
feed by picking up food or trapping food on tentacles and stuffing in mouth
to defend they expel parts of viscera which are sticky and may contain toxins
or they can throw up their digestive system
water oxygen and nutrients are circulated in the echinoderms by
ciliated peritoneum
radial symmetry first evolved in echinoderms for the purpose of
sessile filter feeding
what is ossicle
boney plate that make up endoskeleton
what are sand dollar teeth
broken Aristotle’s lantern
