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Questions and Answers
What is a characteristic of cleavage in protostomes?
What is a characteristic of cleavage in protostomes?
- Indeterminate cleavage
- Radial cleavage
- Determinate cleavage (correct)
- Spiral cleavage
What is unique about the ossicles in echinoderms?
What is unique about the ossicles in echinoderms?
- They are external and covered by muscle
- They have a sponge-like microstructure called stereom (correct)
- They are hollow and contain air
- They are solid and contain collagen
What is the function of the water vascular system in echinoderms?
What is the function of the water vascular system in echinoderms?
- Regulates body temperature
- Aids in sensing the environment
- Performs many important functions including locomotion, respiration, and feeding (correct)
- Supports the skeleton
What is the composition of the fluid in the water vascular system?
What is the composition of the fluid in the water vascular system?
What is the characteristic symmetry of echinoderms?
What is the characteristic symmetry of echinoderms?
What is the function of the ossicles in echinoderms?
What is the function of the ossicles in echinoderms?
What is the name of the phylum that includes sea lilies and feather stars?
What is the name of the phylum that includes sea lilies and feather stars?
What is the developmental origin of echinoderm ossicles?
What is the developmental origin of echinoderm ossicles?
What is the location of the ossicles in echinoderms?
What is the location of the ossicles in echinoderms?
When did echinoderms first appear in the fossil record?
When did echinoderms first appear in the fossil record?
What is the unique microstructure found in echinoderm ossicles?
What is the unique microstructure found in echinoderm ossicles?
What is the primary function of the water vascular system in echinoderms?
What is the primary function of the water vascular system in echinoderms?
What is the characteristic feature of Class Crinoidea?
What is the characteristic feature of Class Crinoidea?
What is the function of the connective tissue in crinoids?
What is the function of the connective tissue in crinoids?
What is the characteristic feature of Class Ophiuroidea?
What is the characteristic feature of Class Ophiuroidea?
What is the function of the Cuvierian tubules in sea cucumbers?
What is the function of the Cuvierian tubules in sea cucumbers?
What is the characteristic feature of Class Asteroidea?
What is the characteristic feature of Class Asteroidea?
What is the function of the ambulacra in echinoderms?
What is the function of the ambulacra in echinoderms?
What is the characteristic feature of Class Echinoidea?
What is the characteristic feature of Class Echinoidea?
Which phylum shares some morphological traits with chordates?
Which phylum shares some morphological traits with chordates?
What is unique about the body plan of crinoids compared to other echinoderms?
What is unique about the body plan of crinoids compared to other echinoderms?
What is the function of the connective tissue in the stems of crinoids?
What is the function of the connective tissue in the stems of crinoids?
What is a characteristic feature of asteroids?
What is a characteristic feature of asteroids?
What is the function of the cancerous ring in sea cucumbers?
What is the function of the cancerous ring in sea cucumbers?
What is a characteristic feature of echinoids?
What is a characteristic feature of echinoids?
What is the function of the Cuvierian tubules in sea cucumbers?
What is the function of the Cuvierian tubules in sea cucumbers?
What is a characteristic feature of hemichordates?
What is a characteristic feature of hemichordates?
What is the name of the group that includes echinoderms and hemichordates?
What is the name of the group that includes echinoderms and hemichordates?
What is a characteristic feature of deuterostomes?
What is a characteristic feature of deuterostomes?
What is the name of the phylum that includes acorn worms and pterobranchs?
What is the name of the phylum that includes acorn worms and pterobranchs?
What is the primary function of the ambulacra in echinoderms?
What is the primary function of the ambulacra in echinoderms?
What is the characteristic body plan of crinoids?
What is the characteristic body plan of crinoids?
What is the function of the cancerous ring in sea cucumbers?
What is the function of the cancerous ring in sea cucumbers?
What is the characteristic feature of Class Ophiuroidea?
What is the characteristic feature of Class Ophiuroidea?
What is the name of the group that includes echinoderms and hemichordates?
What is the name of the group that includes echinoderms and hemichordates?
What is the characteristic feature of echinoids?
What is the characteristic feature of echinoids?
What is the characteristic feature of asteroids?
What is the characteristic feature of asteroids?
What is the function of the Cuvierian tubules in sea cucumbers?
What is the function of the Cuvierian tubules in sea cucumbers?
What is the characteristic feature of hemichordates?
What is the characteristic feature of hemichordates?
What is the characteristic feature of deuterostomes?
What is the characteristic feature of deuterostomes?
What is the primary difference between determinate and indeterminate cleavage in developmental biology?
What is the primary difference between determinate and indeterminate cleavage in developmental biology?
What is the primary function of the ossicles in echinoderms?
What is the primary function of the ossicles in echinoderms?
What is unique about the water vascular system in echinoderms?
What is unique about the water vascular system in echinoderms?
What is the characteristic shape of echinoderm radial symmetry?
What is the characteristic shape of echinoderm radial symmetry?
What is the name of the class of echinoderms that includes sea lilies and feather stars?
What is the name of the class of echinoderms that includes sea lilies and feather stars?
When did echinoderms first appear in the fossil record?
When did echinoderms first appear in the fossil record?
What is the unique microstructure found in echinoderm ossicles?
What is the unique microstructure found in echinoderm ossicles?
What is the developmental origin of echinoderm ossicles?
What is the developmental origin of echinoderm ossicles?
What is the primary function of the water vascular system in echinoderms?
What is the primary function of the water vascular system in echinoderms?
What is the characteristic feature of deuterostomes?
What is the characteristic feature of deuterostomes?
What is the primary function of the ossicles in echinoderms?
What is the primary function of the ossicles in echinoderms?
Which class of echinoderms is characterized by a flexible, snake-like body plan?
Which class of echinoderms is characterized by a flexible, snake-like body plan?
What is unique about the symmetry of irregular echinoids?
What is unique about the symmetry of irregular echinoids?
What is the function of the pharyngeal slits in hemichordates?
What is the function of the pharyngeal slits in hemichordates?
Which class of echinoderms has a characteristic feature of a cancerous ring that encircles the pharynx?
Which class of echinoderms has a characteristic feature of a cancerous ring that encircles the pharynx?
What is the name of the microstructure found in echinoderm ossicles?
What is the name of the microstructure found in echinoderm ossicles?
What is the function of the ambulacra in echinoderms?
What is the function of the ambulacra in echinoderms?
Which class of echinoderms has a characteristic feature of a globose or discoidal test?
Which class of echinoderms has a characteristic feature of a globose or discoidal test?
What is the function of the Cuvierian tubules in sea cucumbers?
What is the function of the Cuvierian tubules in sea cucumbers?
What is the characteristic feature of the arms of asteroids?
What is the characteristic feature of the arms of asteroids?
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Study Notes
Determinate vs Indeterminate Cleavage
- Protostomes: determinate cleavage, cannot take one cell away and have a visible embryo
- Deuterostomes: indeterminate cleavage, up to a certain point, any one cell still has the ability to become a whole embryo
- Deuterostomes that are not vertebrates: Echinoderms, Hemichordates, Cephalochordates, Urochordates
Echinoderms
- Skeletons containing pieces of calcite called ossicles covered by skin
- Ossicles are not solid, but have a sponge-like microstructure called stereom unique to the phylum
- Embryonically, echinoderm ossicles are a true endoskeleton, produced by mesenchymal cells and usually covered by epidermis
- Functionally, however, the majority of ossicles act more like an exoskeleton, lying just under the epidermis and enclosing most other tissues in a flexible but tough covering
- First appeared in the Cambrian
- Water-vascular system with extensions emerging through the skeleton to the outside as tube feet or podia
- Water vascular system performs many important functions including locomotion, respiration, and feeding
- Echinoderms are unique in having a water vascular system
Classes of Echinoderms
Class Crinoidea
- Sea lilies look like flowers
- Feather stars are mobile
- Each arm is an articulated series of ossicles extending outwards from the body
- Cricoids are the only surviving echinoderm to have retained the ancestral body plan of an upwardly directed mouth in the centre of a circle of mucociliary, suspension-feeding, podia-bearing arms
Class Ophiuroidea
- 5 thin, flexible, snake-like arms
- Arms clearly demarcated from central disks and made up of a single row of large calcite plates
- Filter feeding/predatory
Class Asteroidea
- Characteristic star-shaped body plan consisting of a central disc and multiple radiating arms
- Mostly generalist predators, few detritivores
- Asteroids are most easily distinguished from other asterozoa by the structure of the arms
Class Echinoidea
- Skeleton composed of calcitic plates embedded in their skin
- Echinoderms with globose/discoidal test
- Typically with spines
- Diverse feeding strategies from generalists to deposit feeders
- Irregular echinoids have secondarily acquired bilateral symmetry superimposed upon the radial symmetry
Class Holothuroidea
- Generally scavengers
- Distinguishing characteristic - cancerous ring that encircles the pharynx or throat
- The ring serves as an attachment point for muscles operating the oral tentacles and for the anterior ends of other muscles that contract the body longitudinally
- Sea cucumbers have few ossicles and may seem vulnerable to predation, but possess an arsenal of weapons
- Expel white, sticky, toxic threats called Cuvierian tubules from their anus
Phylum Hemichordata
- Hemichordates share some morphological traits with chordates: pharyngeal slits, nerve cord
- Bilateral symmetry
- Tripartite division of body: proboscis, collar, and trunk
- Two extant sub-phyla: Enteropneusts - acorn worms, Pterobranchia
- Echinoderms + Hemichordates form the sister group to chordates - Ambulacraria
- Echinodermata + Hemichordata are grouped as Ambulacraria
- The phylum Chordata is grouped with Echinodermata + Hemichordata within the Deuterostomes
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