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Phyl
ogen
y of
Ext
ant P
hyla
Porif
era
Char
acte
ristic
s Sponges Sole member of the Parazoa Lack true tissues, simplest animals, no nerves
or muscles Choanocytes (collar cells) “Unique
flagellated cells that ingest bacteria and tiny food particles”
Choanocytes look a lot like Choanoflagellates Amoebocytes transfer food to rest of cells Adults sessile, larvae non-sessile “Cells tend to be totipotent (retain zygote’s
ability to form the whole animal)”
Anatomy of Simple Sponge
A More Complex Sponge
Cnid
aria
Cha
ract
eris
tics
Hydras, Jellies, Sea Anenomies, Corals Diploblastic, Carnivorous, Tentacled Lack true muscles (since no mesoderm) Possess nerve net Cnidocytes Cells that shoot stinging or
grasping threads at potential prey Gastrovascular cavity (only one opening) =
Hydrostatic Skeleton Polyps vs. Medusa
Cnidocytes
Cnid
aria
Ana
tom
y
Clas
s An
thoz
oa
A Cnidarian Life Cycle (Obelia)
Plat
yhel
min
th C
hara
cter
istic
s Flatworms (including Flukes and Tapeworms) Bilaterally symmetrical acoelomates Flat, unsegmented, single opening to
gastrovascular cavity Eyespots No circulatory system (instead diffusion) Tapeworms have no digestive system Use ventral cilia to locomote across surfaces
(but some can swim) Ganglia-processing centers
Plan
aria
n An
atom
y
Fluk
e Li
fecy
cle
Tape
wor
m A
nato
my
Rotif
er C
hara
cter
istic
s
Rotifers Very small animals Possess complete digestive tract Pseudocoelomates Aquatic, essentially serve as animals that
approximate the protozoan niche
Nem
atod
e Ch
arac
teris
tics
Round worms (including pinworms & hookworms)
Cuticle that keeps them from drying out Pseudocoelamates—pseudocoelom is used as
a hydrostatic skeleton There are many free-living nematodes as well
as parasitic nemotodes Only longitudinal muscles—whip-like motions Include Trichenella spiralis, Ascaris, and the
filarial worm
A Ro
undw
orm
Mol
lusk
Cha
ract
eris
tics Snails, Slugs, Clams, Squids, Octopi, etc.
Class Polyplacophora, Gastropoda, Class Bivalvia, Class Cephalopoda, etc.
Basic body plan built around a muscular foot, a visceral mass, and a mantle
Not all mollusks have a shell Mollusks lack segmentation Most have an open circulatory system Some (cephalopods) have a closed circulatory
system
Class Polyplacophora (chitons)
Class Gastropoda
Clas
s Bi
valv
ia
Class Cephalopoda
Anne
lid C
hara
cter
istic
s
Segmented worms (earth, marine, leeches) Class Oligochaeta (I.e., earth worms), Class
Polychaeta (e.g., clam worms), Class Hirudinea (I.e., leeches)
Protostomes, Body segments, Closed circulatory system
Clas
s H
irudi
nea
Arth
ropo
d Ch
arac
teris
tics
Insects, Crustaceans, Spiders, Scorpions, Horseshoe crabs, Millipedes, Centipedes, Ticks, Mites, etc.
Protostomes with segmented bodies, jointed appendages, and hard (chitinous) exoskeletons
Also have well-developed senses and open circulation (remember the terms hemocoel and hemolymph)
Subp
hylu
m T
rilob
ita
Subphylum Cheliceriformes
Subphylum Crustacea
Phyl
um E
chin
oder
mat
a
Echi
node
rm C
hara
cter
istic
s Sea stars (Class Asteroida), brittle stars (Class
Ophiuroidea), sea urchin (Class Echinoidea), sea lilies (Class Crinoidea), sea cucumbers (Class Holothuroidea), sea daisies (Class Concentricycloidea)
Coelomates, Deuterostomes Multiple arms, tube feet, water vascular
system, calciferous endoskeleton Larvae are bilaterally symmetrical and adult
forms appear to have radial symmetry (though they are not truly radial animals)
• All 7,000 or so species of echinoderms are marine.• Examples are:
– sea stars– brittle stars– sea urchins– sea lilies and feather stars– sea cucumbers– sea daisies– sand dollars
Star
fish
Anat
omy
Tube
feet
Phyl
um C
hord
ata
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