Includes sea stars, brittle stars, sea urchins, sea dollars, sea cucumbers and
crinoids (fig 33.1)
Echino (= spiny) derma (= skin) SPINY SKIN!
Internal skeleton of calcareous plates called ossicles that protrude through the
skin as spines.
Adult radially symmetrical. Body consisting of 5 radial arms.
Larva bilaterally symmetrical.
Unique WATER VASULAR SYSTEM: series of coelomic water filled canals with hollow
projections called tube feet. (Fig 33.2)
Muscle contraction and hydrostatic pressure in the water vascular system move the
animal forwards.
Divided into 5 classes. The 5 classes are distinguished primarily by the arrangement of
their ossicles.
Class Asterioda (Sea Stars)
Ex. Asterias (Fig 33.3) – common sea star
Ossicles arranged loosely under skin; spines small and blunt
Arms continuous with central disk (Fig 33.4)
Mouth at center & lower oral surface
Anus on upper surface (aboral surface)
Dermal gills – surround the blunt spines of sea stars and used in
respiration via diffusion
Pedicellariae – needed to remove debris from surface
Madreporite – present on the aboral side; it is a sieve connecting the
water vascular system with the environment.
Use arms and tube feet to grip their prey à then evert
their stomach inside the prey à engulf prey tissue.
Class Ophinroidea (Brittle Stars)
Slender branched arms which are demarcated from the central disk (Fig 33.1 d)
Named "brittle" because arms detach
Class Crinoidea (Sea Lilies & Feather Stars)
Ancient echinoderms (Fig 33.1 c)
Oral surface faces up – different from other echinoderms.
Coarse, jointed appearance ; feathery arms.
Class Echinodea (Sea Urchins and Sand Sollars)
Urchins lack distinct arms – Ex: Arbacia
Ossicles fused into a solid shell called a test (Fig. 33.1 e)
Tube feet protrude through the holes in the ossicle
Spines jointed, movable, longer than those of other classes of echinoderms (Fig 33.5)
Mouth contained 5 ossified plates or teeth. This structure is called Aristotle’s
Lantern.
Class Halothuroidea (Sea Cucumbers)
Soft bodies with reduced ossicles and few spines (Fig 33.1 b) Ex: Cucumaria
Mouth surrounded by modified tube feet called tentacles, which help in
capturing prey.
Evisceration – some sea cucumbers respond to stress by rupturing
austeriously and expelling their pharynx, digestive tract, and other organs.
Includes fish, amphibians, reptiles, birds, and mammals.
Characterized by:
a dorsal, hollow nerve cord
a notochord – a cartilaginous rod on the dorsal side of the gut in an
embryo.
Pharyngeal slits
Internal bony skeleton
Divided into 3 subphylums (Urochordata, Cephalochordata, Vertebrata.)
Subphylum Urochordata (Tunicates or Sea Squirts)
Sessile, planktonic, marine
Larvae possess the chordate form but the adult modified to include:
a sieve like basket with pharyngeal gill slits
a body surrounded by a cellulose sac called a tunic
Water enters in current siphon à filtered by
pharyngeal basket à leaves through ex-current siphon (Fig
33.7)
Pharyngeal basket also stores food.
Larval tunicate has bilateral symmetry, dorsal nerve cord, and notochord, but get them
on becoming an adult.
Subphylum Cephalochordata (Lancelets)
Small, fishlike, marine, burrow in sand or mud.
Commonly called aphioxus
Common genus – Branchiostoma (Fig 33.8)
Anus not terminal
Lancelets and vertebrates have a post and tail – another diagnostic trait
of chordates
Seawater enters through mouth à food particles caught in
pharyngeal arches à intestine à
atrium à leaves body through atripore (Fig
33.9)
Subphylum Vertebrata (Fish Birds, Amphibians, Reptiles, and Mammals!)
Presence of vertebral column which replaces the notochord in adults &
surrounds the dorsal nerve cord (Fig 33.10)
Distinct head
Divided into 7 classes.
Class Agnatha (Lampreys and Hagfish)
Lack jaws. (Ex: Petromyzon – Fig 33.11)
Cartilaginous endoskeleton present.
Notochord present.
Seven pharyngeal gill slits (Fig 33.11)
Most lampreys are parasites.
Class Chondrichthyes (Sharks, skates, and rays)
Endoskeleton cartilaginous
Anterior gill arches modified into jaws
Ex: Squalus (dog fish shark – Fig 33.12)
Class Osteichthyes (Bony fish)
Bony endoskeleton
Modified gill arches
Internal air bladders for balance & buoyancy
Gills protected by Operculum (Fig 33.13)
Lateral Line System – sensory pits in skin which run in a line along each
side of the body.
Lateral line system detects water currents and predators or prey causing water
movements.
Class Amphibian (Frogs, Toads, Salamanders)
First land vertebrates
Adults terrestrial but lay eggs in water (Fig 33.14)
Eggs fertilized externally.
Aquatic larval stage – tadpole
Tadpoles metamorphose into adults
Development of legs and lungs first occurred in this class of animals.
Class Reptilia (Turtles, Snakes, Lizards)
Independent of aquatic environment
Internal fertilization (Fig 33.15)
Watertight egg with it’s own supply of nutrients.
Dry skin – does not aid in respiration
Well developed lungs
Poikilothermic – body temperature depends on the environment (Fig 33.17)
Class Aves (Birds)
Only animals with feathers (Fig 33.18)
Homeothermic – maintains a constant body temperature i.e. body temp is not
dependent on the environment
Adaptation to flight includes:
high body temp for high metabolism
lightweight skeleton
efficient respiratory system
heavy muscular tissue at breast to move wings.
Class Mammalia
Body covered with insulating fat and hair
Constant body temperature (Fig 33.20)
Well developed circulatory system – 4 chambered heart
Young ones nourished by milk – produced by mammary glands of the mother.
