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Summary Finals Compilation 2
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15_PHYLUM ECHINODERMATAGENERAL CHARACTERISTICS
- “spiny-skinned”
- highly-organized marine invertebrates
- coelomate
- thrives in marine environment
- primitive senses
- water vascular system
DISTINCT CHARACTERISTICS
- Calcareous skeleton (crystalline calcite)
- Non-parasitic
- Tube feet (podia)
- primitive bilateral symmetry masked by a strong 5-fold radial symmetry
ARTHOPODA SIMILARITIES ECHINODERMATA
-exoskeleton -bilaterally -skeleton enclosed in
symmetrical soft tissues
-respiratory
system -highly varied -osmotic regulation
-chitinous -calcareous skeleton
skeleton
ECHINODERMATA SIMILARITIES CHORDATA
-absence of -bilaterally -notochord
notochord symmetrical
-phosphatic
-calcite skeleton -larval stage skeleton
-tube feet -central -respiratory
nervous system
-water vascular
system
system
-body fluid
proteins
,MODE OF LIFE
GENERAL
- known only to live in marine environments, though some can be found in
brackish water
- vary from filter feeders to active predators
- filter feeders - mud passes through the alimentary tract
- no true planktonic echinoderms
CRINOIDS
- live in strong currents, such as zone of breaking waves
- shallow waters to abyssal depths
- filter feeders
- two types: stem-bearing / stalked and free-swimming
ASTEROIDS AND OPHIUROIDS
- sea stars and brittle stars
- littoral zones and deep waters
- muddy bottom
- survival mechanism: fast / slow movement
ECHINOIDS
- mobile algae grazers
- most burrow, but some use their spines or tube feet to anchor themselves
- found from intertidal zone to deep marine
HOLOTHUROIDS
- muddy bottom
- survival mechanisms
o slow creeping
▪ swimming
▪ burrowing
- tube feet
SEXUAL REPRODUCTION
- simple reproductive organs
- the eggs are released and fertilized externally
- larva is bilaterally symmetrical, is free-swimming, and lacks calcareous skeleton
,ASEXUAL REPRODUCTION
- Transverse Fission
- Disc splitting into two
- Regrowth of missing parts occur
- In some stars, only a single arm is needed. Most need the disk to form a new
individual
- Larva of sea stars and brittle stars are also capable of transverse fission
ANATOMY AND STRUCTURE
HARD PARTS
Endoskeleton
- calcareous plates (ossicles)
- rigid shell (test)
- divided into two: calyx or theca and appendages
- formed by internal secretion
- honeycomb structure
SOFT PARTS
- water vascular system
o in primitive forms
▪ water is circulated
▪ for respiration and feeding
- not for locomotion
- in modern forms
o passes through the madreporite and through action of cilia
, SOFT PARTS
- digestive / excretory system
o has mouth, esophagus, stomach and anus
o some can extend stomach
- radial canal
o small rounded muscular sacs (ampullae)
o podia or tube feet
- nervous system
o no center of function (brain)
o central nerve ring that branches out
o enables echinoderms to react to touch stimuli
BASIS OF CLASSIFICATION
- Based on Moore, Lalicker, Fischer
- Attached (stem-bearing) and unattached (free-swimming)
- Further classified based on their general form and organization of the body,
nature of the water circulatory system, and the structural plan of skeletal
elements
MAJOR FOSSIL GROUPS
- Subphylum Pelmatozoa
o Class Eocrinoidea
o Class Paracrinoidea
o Class Carpoidea
o Class Edrioasteroidea
o Class Cystoidea
o Class Blastoidea
o Class Crinoidea
- Subphylum Eleutherozoa
o Class Holothuroidea
o Class Stelleroidea
▪ Subclass Somasteroidea
▪ Subclass Asteroidea
▪ Subclass Ophiuroidea
o Class Echinoidea
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