Transcript Phylum Porifera – Diversity and Structure

Phylum Echinodermata – Diversity and Class
Characteristics
 Phylum Characteristics: marine; deuterostomes; spiny endo-
skeleton, water-vascular system, pedicellariae (minute
pincers), dermal branchiae, pentaradial symmetry
 Diversity and Class Characteristics
 Class Asteroidea: sea stars (~1,500 species), incl. sunflower stars
 Class Ophiuroidea: brittle stars (~2,000 species), incl. basket stars;
arms slender w/ plates, w/o pedicellariae; no suckers on tube feet
 Class Echinoidea: sea urchins, sea biscuits, and sand dollars (~950
species); internal test; movable spines; species with reduced tests
often venomous with warning coloration; bore into rock
 Class Holothuroidea: sea cucumbers (~1,150 species); reduced
spines (soft bodied); elongation along oral-aboral axis
 Class Crinoidea: sea lilies and feather stars (~625 species); most
stalked, sessile, w/ oral sides up; deep-sea and Indo-Pacific forms
Fig. 22.3
Fig. 22.4
Fig. 22.14
Fig. 22.18
Fig. 22.20
Fig. 22.24
Fig. 22.29
Phylum Echinodermata: Structure and Function
 External Features: most with spines and pedicellariae; oral end usually




against substratum; anus, madreporite, and dermal branchiae
(papulae) on aboral end (excl. brittle stars); tube feet often within
ambulacral grooves
Feeding and Digestion: include predators (most sea stars), grazers (most
urchins), deposit feeders and detritivores (cucumbers and brittle stars);
cardiac stomach everted by sea stars for feeding on bivalves; urchins
with five calcareous jaws and Aristotle’s lantern; cucumbers with
retractable oral tentacles; mucociliary feeding with crinoids
Water-vascular System: madreporite (filter) leads to stone canal, ring
canal, radial canals; water flows into tube feet (can expand)
Reproduction, Regeneration, and Autotomy: most with separate sexes;
regeneration (some with asexual reproduction; autotomy most
common in brittle stars); sea cucumbers evert internal organs as
distraction (some with sticky Cuvierian tubules)
Development: metamorphosis with bilateral, free-swimming larvae
Fig. 22.5
Fig. 22.7
Fig. 22.15
Fig. 22.6
Fig. 22.9
Fig. 22.22
Fig. 22.23
Fig. 22.26
Fig. 22.28
Fig. 22.11
Fig. 22.12
Introduction to Phylum Chordata
 Phylum Characteristics (present at some stage of life cycle)
 Notochord: internal skeletal rod; allows muscle attachment
 Dorsal, hollow nerve cord: enlarged at anterior to form brain in vertebrates




(protected by cartilaginous or bony cranium)
Pharyngeal grooves and pouches: slits in aquatic forms; used for filter
feeding in tunicates; gill slits in fishes
Post-anal tail: allows propulsion in water; related to balance in non-aquatic
vertebrates; vestigial coccyx in humans
Endostyle (or thyroid) gland: at floor of pharynx; endostyle gland produces
mucus for food capture and iodinated proteins (homologue to thyroid)
Other Characteristics: bilateral symmetry, segmentation of outer body wall
(myomeres), three germ layers, well-developed coelom; deuterostomes
 Origin of the Vertebrates
 Hypothesis of Larval Evolution (Garstang, 1928): tadpole larvae of tunicates
failed to metamorphose and developed gonads in juvenile stage
(paedomorphosis), leading to vertebrate lineage
Fig. 23.1
Fig. 23.2
Fig. 23.3
Fig. 23.12
Diversity and Characteristics of Chordates
 Subphylum Urochordata (Tunicata): ~1,600 species; exhibit
external tunic (cellulose)



Class Ascidiacea: sea squirts (sessile tunicates); filter feed via
siphons and pharyngeal slits; tadpole larvae with all chordate
features; hermaphrodites
Class Thaliacea: pelagic tunicates (salps); solitary & colonial forms
Class Appendicularia: larvaceans; produce mucus houses for
feeding on bacteria (discard as clog  marine snow)
 Subphylum Cephalochordata: lancelets (Amphioxis, or
Branchiostoma); 3-7 cm long; laterally flattened; live in beach
sand; possess all chordate plus vertebrate-like features
(hepatic cecum stores glycogen, segmented trunk
musculature)
 Subphylum Vertebrata (Craniata): with cranium; most with
vertebrae
Fig. 23.5
Fig. 23.7
Fig. 23.4 and 23.6
Continued below
Fig. 23.8
CO 23
Fig. 23.9
Fig. 23.13