Invertebrate Body Plans

Phylum Porifera

Sponges lack true tissue layers and organ systems

Mesophyll layer

Layer in sponges where specialized cells are found

Epidermis

Outer layer of cells covering the sponge

Filter feeders

Organisms that absorb nutrients from circulating water

Collar cells

Cells in sponges with flagella for water circulation

Spicules

Spike-shaped structures providing structure to sponges

Amoebocytes

Cells in sponges that move, make spicules, and digest food

Phylum Platyhelminthes

Flatworms with 3 germ layers and internal organs

Cephalization

Presence of a head region with sensory organs

Acoelomates

Animals lacking a fluid-filled body cavity

Turbellarians

Aquatic flatworms feeding on organic matter

Flukes

Parasitic flatworms infecting internal organs

Tapeworms

Parasitic flatworms living in the host's intestine

Hermaphrodites

Organisms with both male and female reproductive organs

Phylum Cnidaria

Includes jellyfish, hydra, sea anemone, and corals

Cnidocytes

Stinging cells in cnidarians for prey capture

Nematocysts

Poison-filled structures in cnidocytes for prey capture

Hydrostatic skeleton

Internal support system in cnidarians

Phylum Nematoda

Roundworms with bilateral symmetry and a digestive system

Pseudocoelomates

Animals with a partially lined fluid-filled body cavity

Ascaris

Roundworm living in the host's intestines

Trichinella

Roundworm causing tissue burrowing in hosts

C.elegans

Non-parasitic roundworm used in genetic research

Phylum Annelida

Segmented worms with a one-way digestive tract

Septa

Internal walls separating segments in annelids

Clitellum

Thickened segments for reproduction in annelids

Nephridia

Tubes for excreting liquid waste in annelids

Phylum Mollusca

Soft-bodied animals with shells like gastropods

Gastropod

Shell-less or single-shelled mollusk with a muscular foot and slime production

Mantle

Soft outer layer of a mollusk's body that secretes the shell

Visceral mass

Internal organs of a mollusk

Radula

Tongue-like organ covered with tiny teeth, used by gastropods for feeding

Herbivorous gastropod

Gastropod that uses its radula to scrape up algae or tear apart leaves

Carnivorous gastropod

Gastropod that uses its radula to drill through the shells of prey and tear up their soft tissue

Aquatic gastropod

Gastropod that lives in water

Terrestrial gastropod

Gastropod that lives on land

Eye stalks

Specialized structures in gastropods that sense light and some movement

Snail

Example of a gastropod

Conch

Example of a gastropod

Slug

Example of a gastropod

Bivalve

Organism with two shells held together by muscles, filter feeders

Foot

Part of a bivalve used for burrowing into sand

Pearl

Formation created when a foreign object is coated with shell-like material secreted by the mantle of a bivalve

Clam

Example of a bivalve

Oyster

Example of a bivalve that can produce pearls

Mussel

Example of a bivalve

Scallop

Example of a bivalve

Cephalopod

Soft-bodied mollusk with a head attached to a foot divided into tentacles or arms

Nautilus

Cephalopod with a spiral shell and tentacles

Squid

Cephalopod with an internal shell and a siphon for movement

Octopus

Cephalopod without a shell, uses siphon for movement

Chromatophores

Specialized structures in cephalopods that enable them to change skin color

Ink Sacs

Specialized structures in squid and octopus that produce ink for defense

Arthropod

Segmented invertebrate with joined appendages and an exoskeleton

Crustacean

Aquatic arthropod with two pairs of antennae and a cephalothorax and abdomen

Pill bug

Example of a crustacean that lives on land

Arachnid

Arthropod with two body sections, eight legs, and mouth parts called chelicerae

Spinnerets

Organs in spiders that produce silk for web-spinning

Insect

Arthropod with three body segments, compound eyes, and six legs

Ant

Example of an insect with mandibles for sawing and grinding food

Butterfly

Example of an insect with a proboscis for sucking up nectar

Metamorphosis

Series of changes during which an insect larvae becomes an adult

Starfish

Example of an echinoderm with a water vascular system and tube feet

Sea cucumber

Echinoderm that can shoot out long tubules or its whole digestive system for defense

Sea urchin

Example of an echinoderm with spines and tube feet

Sand dollar

Example of an echinoderm with a flattened, disk-like shape