Major Animal Phyla Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, Arthropoda, Echinodermata, and Chordata

Overview: Check This Out First

Phylum Porifera: Sponges Have no definite shape – asymmetrical No tissues or organs Colony of specialized cells Immobile Good powers of regeneration Skeleton of spongin and spicules

CLASSES OF SPONGES Class Calcarea – has calcium carbonate spicules Class Hexactinellida – glass sponges with spicules of silica Class Demospongiae – no spicules, only spongin

Phylum Cnidaria stinging-celled animals Jellyfishes, corals, anemones Radial symmetry Two tissue layers with inner mesoglea Primitive nerve net but no brain 2-way digestive tract Stinging cells for capturing food.

CLASSES OF CNIDARIANS Class Hydrozoa – Hydra, Portuguese-Man-of-War, Obelia; mostly polyp or hydroid stage Class Scyphozoa – true jellyfishes; mostly medusa stage Class Anthozoa – corals, anemones Class Cubozoa – box jellies

Phylum Platyhelminthes flatworms First animals to exhibit bilateral symmetry Have primitive brain 3 tissue layers Includes free-living flatworms and parasitic flatworms (tapeworms, flukes)

CLASSES OF FLATWORMS Class Turbellaria – free-living flatworms Class Cestoda – tapeworms Class Trematoda - flukes

Phylum Annelida segmented worms Earthworms, sandworms, leeches One-way digestive system Have well-developed digestive and circulatory systems

CLASSES OF ANNELIDS Class Oligochaeta – earthworms, bloodworms; oligo- means “few” and chaeta means a “bristle” or stout hair Class Polychaeta – many bristles and parapodia (fleshly lobes to “walk” with Class Hirudinea – leeches (most are NOT bloodsuckers)

Phylum Mollusca- soft bodied animals includes snails, slugs, nudibranchs, chitons, limpets, clams, oysters, squid, octopus, nautilus, etc. Either have no shell, one shell, or two shells Many have hard mouth parts (radula in gastropods, beak in cephalopods).

CLASSES OF MOLLUSCS Class Gastropoda – snails, slugs, conchs, nudibranchs; have either no shell or one shell; name means “stomach foot” Class Bivalvia – clams, oysters, mussels; have two shells that hinge together Class Polyplacophora – chitons; snail-like with 8 embedded plates on its back Class Cephalopoda – squid, octopus, nautilus, cuttlefish; name means “head foot”; well-developed nervous system

Phylum Arthropoda – joint-legged animals includes insects, crustaceans, centipedes, millipedes, and arachnids exoskeleton made of chitin must shed shell to grow

CLASSES OF ARTHROPODS Class Crustacea – shrimps, lobsters, crabs, crawfishes Class Amphipoda – small; called scuds Class Isopoda – sea lice; some are parasitic Class Stomatopoda – mantis shrimps Class Pycnogonida – sea spiders Class Merostomata – horseshoe crabs Class Cirripedia - barnacles

Phylum Echinodermata – spiney-skinned animals includes sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers, and crinoids reverted back to radial symmetry (radial in adults / bilateral in larvae) tube feet and water vascular system Most exhibit pentamerism

WHY ARE ECHINODERMS RANKED SO HIGH? Clues from embryology – study of the early development of animals Protostome – blastopore forms the mouth in all animals except echinoderms and chordates Deuterostomes – blastopore forms the anus in echinoderms and chordates

CLASSES OF ECHINODERMS Class Asteroidea – sea stars Class Ophiuroidea – brittle stars, serpent stars Class Echinoidea – sea urchins, sand dollars Class Holothuroidea – sea cucumbers Class Crinoidea – sea lilies, feather stars

Phylum Chordata Includes fish, amphibians, reptiles, birds, and mammals Dorsal hollow nerve tube Notochord Pharyngeal gill slits Post anal tail