Porifera ANCESTRAL PROTIST Cnidaria Common ancestor of all animals Lophotrochozoa Eumetazoa Ecdysozoa Bilateria 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) Ectoprocta (4,500 species) Brachiopoda (335 species) 0.1 mm A brachiopod Ectoprocts A marine flatworm A rotifer (LM) Annelida (16,500 species) Acanthocephala (1,100 species) Nemertea (900 species) Cycliophora (1 species) Curved hooks 100 m An acanthocephalan (LM) A cycliophoran (colorized SEM) A marine annelid Mollusca (93,000 species) A ribbon worm Lophotrochozoa An octopus
Priapula (16 species) Loricifera (10 species) Onychophora (110 species) 50 m A loriciferan (LM) A priapulan An onychophoran Arthropoda (1,000,000 species) Nematoda (25,000 species) Tardigrada (800 species) 100 m A roundworm (colored SEM) Tardigrades (colorized SEM) A scorpion (an arachnid) Ecdysozoa
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 Eumetazoa Ecdysozoa Deuterostomia
(d) Sea anemones and othermembers of class Anthozoaexist only as polyps. (b) Many species of jellies (classScyphozoa), including thespecies pictured here, are bioluminescent. The largest scyphozoans have tentaclesmore 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 andother large prey, is more potent than cobra venom. (a) These colonial polyps are members of class Hydrozoa.
Lophophore Lophophore Lophophore Brachiopods have a hinged shell. The two parts of the shell are dorsal and ventral. Ectoprocts, such as this sea mat (Membranipora membranacea), are colonial lophophorates. (a) (b) (c) In phoronids such as Phoronis hippocrepia, the lophophore and mouth are at one end of an elongated trunk.
Cephalopods: Squid (top left and bottom left), nautilus (top right), octopus (bottom right)
50 µm (c) (b) (a) Scorpions have pedipalps that are pincers specialized for defense and the capture of food. The tip of the tail bears a poisonous stinger. Dust mites are ubiquitous scavengers in human dwellings but are harmless except to those people who are allergic to them (colorized SEM). Web-building spiders are generally most active during the daytime.
Crustaceans: Lobster (top left), banded coral shrimp (bottom left), barnacles (right)
Cnidaria Porifera Chordata Echinodermata Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Deuterostomia Bilateria Eumetazoa Ancestral colonial choanoflagellate
(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)