PHYLUM PORIFERA
(sponges) Aquatic; lack true tissues and organs; motile larvae and sessile adults; filter feeders; internal skeleton made up of spongin and/or spicules of calcium carbonate or silica. Examples: Venus' flower basket, bath sponge, tube sponge.
PHYLUM CNIDARIA
(cnidarians) Previously known as coelenterates; aquatic; mostly carnivorous; two layers of true tissues; radial symmetry; tentacles bear stinging nematocysts; many alternate between polyp and medusa body forms; gastrovascular cavity.
Class Hydrozoa
Spend most of their time as polyps; colonial or solitary; life cycle typically includes a medusa generation that reproduces sexually and a polyp generation that reproduces asexually. Examples: hydra, Portuguese man-of-war.
Class Scyphozoa
Spend most of their time as medusas; some species bypass polyp stage. Examples: lion's mane jellyfish, moon jelly, sea wasp.
Class Anthozoa
Colonial or solitary polyps; no medusa stage. Examples: reef coral, sea anemone, sea pen, sea fan.
PHYLUM PLATYHELMINTHES
(flatworms) Three layers of tissues (endoderm, mesoderm, ectoderm); bilateral symmetry; some cephalization; acoelomate; free-living or parasitic.
Class Turbellaria
(turbellarians) Free-living carnivores and scavengers; live in fresh water, in salt water, or on land; move with cilia. Example: planarians.
Class Trematoda
(flukes) Parasites; life cycle typically involves more than one host. Examples: Schistosoma, liver fluke.
Class Cestoda
(tapeworms) Internal parasites; lack digestive tract; body composed of many repeating sections (proglottids). Example: tapeworms.
PHYLUM NEMATODA
(roundworms) Digestive system has two openings—a mouth and an anus; pseudocoelomates. Examples: Ascaris lumbricoides, hookworms, Trichinella.
PHYLUM ANNELIDA
(segmented worms) Body composed of segments separated by internal partitions; digestive system has two openings; coelomate; closed circulatory system.
Class Polychaeta
(polychaetes) Live in salt water; pair of bristly, fleshy appendages on each segment; some live in tubes. Examples: sandworm, fanworm, feather-duster worm.
Class Oligochaeta
(oligochaetes) Lack appendages; few bristles; terrestrial or fresh water. Examples: Tubifex, earthworm.
Class Hirudinea
(leeches) Lack appendages; carnivores or blood-sucking external parasites; most live in fresh water. Example: medicinal leech (Hirudo medicinalis).
PHYLUM MOLLUSCA
(mollusks) Soft-bodied; often possess a hard, calcified shell secreted by a mantle; muscular foot; digestive system with two openings; coelomates.
Class Bivalvia
(bivalves) Two-part hinged shell; wedge-shaped foot; typically sessile as adults; primarily aquatic; some burrow in mud or sand. Examples: clam, oyster, scallop, mussel.
Class Gastropoda
(gastropods) Use broad, muscular foot in movement; most have spiral, chambered shell; some lack shell; distinct head; some terrestrial, others aquatic; many are cross-fertilizing hermaphrodites. Examples: snail, slug, nudibranch, sea hare, sea butterfly.
Class Cephalopoda
(cephalopods) Foot is divided into tentacles; live in salt water; closed circulatory system. Examples: octopus, squid, nautilus, cuttlefish.
PHYLUM ARTHROPODA
(arthropods) Exoskeleton of chitin; jointed appendages; segmented body; many undergo metamorphosis during development; open circulatory system; largest animal phylum.
Subphylum Trilobita
(trilobites) Two furrows running from head to tail divide body into three lobes; one pair of unspecialized appendages on each body segment; each appendage divided into two branches—a gill and a walking leg; all extinct.
Subphylum Chelicerata
(chelicerates) First pair of appendages specialized as feeding structures called chelicerae; body composed of two parts—cephalothorax and abdomen; lack antennae; most terrestrial. Examples: horseshoe crab, tick, mite, spider, scorpion.
Subphylum Crustacea
(crustaceans) Most aquatic; most live in salt water; two pairs of antennae; mouthparts called mandibles; appendages consist of two branches; many have a carapace that covers part or all of the body. Examples: crab, crayfish, pill bug, water flea, barnacle.
Subphylum Uniramia
Almost all terrestrial; one pair of antennae; mandibles; unbranched appendages.
Class Chilopoda
(centipedes) Long body consisting of many segments; one pair of legs per segment; poison claws for feeding; carnivorous.
Class Diplopoda
(millipedes) Long body consisting of many segments; two pairs of legs per segment; mostly herbivorous.
Class Insecta
(insects) Body divided into three parts—head, thorax, and abdomen; three pairs of legs and usually one or two pairs of wings attached to thorax; some undergo complete metamorphosis. Examples: termite, ant, beetle, dragonfly, fly, moth, grasshopper.
PHYLUM ECHINODERMATA
(echinoderms) Live in salt water; larvae have bilateral symmetry; adults typically have radial symmetry; endoskeleton; tube feet; water vascular system used in respiration, excretion, feeding, and locomotion; deuterostomes.
Class Crinoidea
(crinoids) Filter feeders; feathery arms; mouth and anus on upper surface of body disk; some sessile. Examples: sea lily, feather star.
Class Asteroidea
(sea stars) Star-shaped; carnivorous; bottom dwellers; mouth on lower surface. Examples: crown-of-thorns sea star, sunstar.
Class Ophiuroidea
Small body disk; long armored arms; most have only five arms; lack an anus; most are filter feeders or detritus feeders. Examples: brittle star, basket star.
Class Echinoidea
Lack arms; body encased in rigid, boxlike covering; covered with spines; most grazing herbivores or detritus feeders. Examples: sea urchin, sand dollar, sea biscuit.
Class Holothuroidea
(sea cucumbers) Cylindrical body with feeding tentacles on one end; lie on their side; mostly detritus or filter feeders; endoskeleton greatly reduced.
PHYLUM CHORDATA
(chordates) Dorsal hollow nerve cord, notochord, pharyngeal pouches, and a muscular tail during at least part of development.
Subphylum Urochordata
(tunicates) Live in salt water; tough outer covering; display chordate features during larval stages; many adults sessile, some free-swimming. Examples: sea squirt, sea peach, salp.
Subphylum Cephalochordata
(lancelets) Fishlike; live in salt water; filter feeders; no internal skeleton. Example: Branchiostoma.
Subphylum Vertebrata
Most possess a vertebral column (backbone) that supports and protects dorsal nerve chord; endoskeleton; distinct head with a skull and brain.
Class Myxini
(hagfishes) Mostly scavengers; live in salt water; short tentacles around mouth; rasping tongue; extremely slimy; open circulatory system.
Class Cephalaspidomorphi
(lampreys) Larvae filter feeders; adults are parasites whose circular mouth is lined with rasping toothlike structures; many live in both salt water and fresh water during the course of their lives.
Class Chondrichthyes
(cartilaginous fishes) Have jaws, fins, and endoskeleton of cartilage; most live in salt water; typically several gill slits; tough small scales with spines; ectothermic; two-chambered heart; males possess structures for internal fertilization. Examples: shark, ray, skate, chimaera, sawfish.
Class Osteichthyes
(bony fishes) Bony endoskeleton; aquatic; ectothermic; well-developed respiratory system, usually involving gills; possess swim bladder; paired fins; divided into two groups—ray-finned fishes, which include most living species, and lobe-finned fishes, which include lungfishes and the coelacanth. Examples: salmon, perch, sturgeon, tuna, goldfish, eel.
Class Amphibia
(amphibians) Adapted primarily to life in wet places; ectothermic; most carnivorous; smooth, moist skin; typically lay eggs that develop in water; usually have gilled larvae; most have three-chambered heart; adults either aquatic or terrestrial; terrestrial forms respire using lungs, skin, and/or lining of the mouth.
Order Urodela
(salamanders) Possess tail as adults; carnivorous; usually have four legs; usually aquatic as larvae and terrestrial as adults.
Order Anura
(frogs and toads) Adults in almost all species lack tail; aquatic larvae called tadpoles; well-developed hind legs adapted for jumping.
Order Apoda
(legless amphibians) Wormlike; lack legs; carnivorous; terrestrial burrowers; some undergo direct development; some viviparous. Example: caecilians.
Class Reptilia
(reptiles) As a group, adapted to fully terrestrial life, some live in water; dry, scale-covered skin; ectothermic; most have three-chambered hearts; internal fertilization; amniotic eggs typically laid on land; extinct forms include dinosaurs and flying reptiles.
Order Sphenodonta
(tuataras) Lack internal ears; primitive scales; found only in New Zealand; carnivorous. One species: Sphenodon punctatus.
Order Squamata
(lizards and snakes) Most carnivorous; majority terrestrial; lizards typically have legs; snakes lack legs. Examples: iguana, gecko, skink, cobra, python, boa.
Order Crocodilia
(crocodilians) Carnivorous; aquatic or semiaquatic; four-chambered heart. Examples: alligator, crocodile, caiman, gavial.
Order Testudines
(turtles and tortoises) Bony shell; ribs and vertebrae fused to upper part of shell; some terrestrial, others semiaquatic or aquatic; all lay eggs on land. Examples: snapping turtle, tortoise, hawksbill turtle, box turtle.
Class Aves
(birds) Endothermic; feathered over much of body surface; scales on legs and feet; bones hollow and lightweight in flying species; four-chambered heart; well-developed lungs and air sacs for efficient air exchange. Examples: owl, eagle, duck, chicken, pigeon, penguin, sparrow, stork.
Class Mammalia
(mammals) Endothermic; subcutaneous fat; hair; most viviparous; suckle young with milk produced in mammary glands; four-chambered heart; most have four legs; use lungs for respiration.
Order Monotremata
(monotremes) Exhibit features of both mammals and reptiles; possess a cloaca; lay eggs that hatch externally; produce milk from primitive nipplelike structures. Examples: duckbill platypus, short-beaked echidna.
Order Marsupialia
(marsupials) Young develop in the female's uterus but emerge at very early state of development; development completed in mother's pouch. Examples: opossum, kangaroo, koala.
Order Insectivora
(insectivores) Have long, narrow snouts and sharp claws for digging. Examples: shrew, mole, hedgehog.
Order Chiroptera
(bats) Flying mammals, with forelimbs adapted for flight; most nocturnal; most navigate by echolocation; most species feed on insects, nectar, or fruits; some species feed on blood. Examples: fruit bat, flying fox, vampire bat.
Order Primates
(primates) Highly developed brain and complex social behavior; excellent binocular vision; quadrupedal or bipedal locomotion; five digits on hands and feet. Examples: lemur, monkey, chimpanzee, human.
Order Xenarthra
(xenarthrans) Teeth reduced or absent; feed primarily on social insects, such as termites and ants. Examples: anteater, armadillo.
Order Lagomorpha
(lagomorphs) Small herbivores with chisel-shaped front teeth; generally adapted to running and jumping. Examples: rabbit, pika, hare.
Order Rodentia
(rodents) Mostly herbivorous but some omnivorous; sharp front teeth. Examples: rat, beaver, guinea pig, hamster, gerbil, squirrel.
Order Cetacea
(cetaceans) Fully adapted to aquatic existence; feed, breed, and give birth in water; forelimbs specialized as flippers; external hindlimbs absent; many species capable of long, deep dives; some use echolocation to navigate; communicate using complex auditory signals. Examples: whale, porpoise, dolphin.
Order Carnivora
(carnivores) Mostly carnivorous; live in salt water or on land; aquatic species must return to land to breed. Examples: seal, bear, raccoon, weasel, skunk.
Order Proboscidea
(elephants) Herbivorous; have trunks; largest land animal. Examples: Asian elephant, African elephant.
Order Sirenia
(sirenians) Aquatic herbivores; slow-moving; front limbs modified as flippers; hindlimbs absent; little body hair. Examples: manatee, sea cow.
Order Perissodactyla
(odd-toed ungulates) Hoofed herbivores; odd number of digits on each foot; teeth, jaw, and digestive system adapted to plant material. Examples: horse, donkey, rhinoceros, tapir.
Order Artiodactyla
(even-toed ungulates) Hoofed herbivores; hoofs derived from two digits on each foot; digestive system adapted to thoroughly process tough plant material. Examples: sheep, cow, hippopotamus, antelope, camel, giraffe, pig.
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