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Figure 33.0 Ochre sea stars, Pisaster ochraceus
Porifera
ANCESTRAL
PROTIST
Lophotrochozoa
Bilateria
Eumetazoa
Common
ancestor of
all animals
Cnidaria
Ecdysozoa
Deuterostomia
Porifera (5,500 species)
Placozoa (1 species)
0.5 mm
A sponge
Cnidaria (10,000 species)
A placozoan (LM)
Ctenophora (100 species)
A jelly
Acoela (400 species)
1.5 mm
Acoel flatworms (LM)
A ctenophore, or comb jelly
Platyhelminthes
(20,000 species)
Rotifera
(1,800 species)
0.1 mm
Ectoprocta
(4,500 species)
Ectoprocts
A marine flatworm
Acanthocephala
(1,100 species)
Nemertea
(900 species)
Brachiopoda
(335 species)
A brachiopod
A rotifer (LM)
Cycliophora
(1 species)
Annelida
(16,500 species)
Curved
hooks
100 m
An acanthocephalan (LM)
Mollusca
(93,000 species)
A ribbon worm
An octopus
A cycliophoran
(colorized SEM)
Lophotrochozoa
A marine annelid
Loricifera (10 species)
Priapula (16 species)
Onychophora (110 species)
50 m
A loriciferan (LM)
A priapulan
An onychophoran
Nematoda
(25,000 species)
Tardigrada
(800 species)
Arthropoda
(1,000,000 species)
100 m
A roundworm
(colored SEM)
Ecdysozoa
Tardigrades
(colorized SEM)
A scorpion (an arachnid)
Hemichordata
(85 species)
Chordata
(52,000 species)
A tunicate
Echinodermata (7,000 species)
An acorn worm
Deuterostomia
A sea urchin
Figure 33.UN01
Porifera
Cnidaria
Lophotrochozoa
Ecdysozoa
Deuterostomia
Figure 33.UN02
Porifera
Cnidaria
Lophotrochozoa
Deuterostomia
Eumetazoa
Ecdysozoa
(a) These colonial polyps are members of
class Hydrozoa.
(b) Many species of jellies (class
Scyphozoa), including the
species pictured here, are
bioluminescent. The largest
scyphozoans have tentacles
more than 100 m long
dangling from a bell-shaped
body up to 2 m in diameter.
(c) The sea wasp (Chironex
fleckeri) is a member of
class Cubozoa. Its poison,
which can subdue fish and
other large prey, is more
potent than cobra venom.
(d) Sea anemones and other
members of class Anthozoa
exist only as polyps.
Anatomy of a planarian
A rotifer
Lophophore
Lophophore
Lophophore
(a) Ectoprocts, such as this sea (b) In phoronids such as
mat (Membranipora
Phoronis hippocrepia, the
membranacea), are colonial
lophophore and mouth
lophophorates.
are at one end of an
elongated trunk.
(c) Brachiopods have a hinged shell.
The two parts of the shell are
dorsal and ventral.
Table 33.3 Major Classes of Phylum Mollusca
A chiton
The results of torsion in a gastropod
A bivalve: Scallop
Anatomy of a clam
Cephalopods: Squid (top left and bottom left), nautilus (top right), octopus (bottom right)
Anatomy of an earthworm
Classes of Phylum Annelida
Parapodia
Free-living nematode
External anatomy of an arthropod
50 µm
(a) Scorpions have pedipalps that are pincers (b) Dust mites are ubiquitous scavengers in (c) Web-building spiders are generally
specialized for defense and the capture of
human dwellings but are harmless except
most active during the daytime.
food. The tip of the tail bears a poisonous
to those people who are allergic to them
stinger.
(colorized SEM).
Class Dipolopoda (millipedes)
Anatomy of a grasshopper, an insect
Metamorphosis of a butterfly
Crustaceans: Lobster (top left), banded coral shrimp (bottom left), barnacles (right)
Eumetazoa
Ancestral colonial
choanoflagellate
Cnidaria
Porifera
Bilateria
Chordata
Echinodermata
Other bilaterians (including
Nematoda, Arthropoda,
Mollusca, and Annelida)
Deuterostomia
Anatomy of a sea star
(a) A sea star (class Asteroidea)
(b) A brittle star (class Ophiuroidea)
(c) A sea urchin (class Echinoidea)
(d) A feather star (class Crinoidea)
(e) A sea cucumber (class Holothuroidea)
(f) A sea daisy (class Concentricycloidea)