Simplest Animals and Protostomes

Protostome

an animal whose mouth is formed from the blastopore

Lophotrochozoans

grow continuously when conditions are good

Ecdysozoans

shed their exoskeletons through a process called ecdysis

Lophotrochozoan lineages

Rotifera

Platyhelminthes

Annelida

Mollusca

Annelida

phylum of segmented worms

Mollusca

(snails, clams, squids, octopuses) have a soft body that in many species is protected by a hard shell

Platyhelminthes

Phylum of flatworms

Rotifera

Phylum of worms with a crown of cilia surrounding the mouth

Ecdysozoans lineages

arthropda and nematoda

Porifera

sponges

Ctenophora

comb jellies

Cnidaria

jellyfish, corals, sea anemones

Sessile

Describes an organism that remains attached to a surface for its entire life and does not move

Choanocytes

specialized cell in sponges that uses a flagellum to move a steady current of water through the sponge

Benthic

bottom dwelling

suspension feeders

An aquatic animal, such as a clam or a baleen whale, that sifts small food particles from the water

Mesoglea

A jelly-like substance between the inner layer and outer layer of cells in a cnidarian

monophyletic

ALL descendants came from one common ancestor

lophophore

In some lophotrochozoan animals, including brachiopods, a crown of ciliated tentacles that surround the mouth and function in feeding.

trochophore

free-swimming larval stage of an aquatic mollusk

corona

creates a water current that draws food into the mouth

hydrostatic skeleton

A fluid skeleton in many soft-bodied invertebrates, including annelids, that allows an organism to change shape but not volume.

Acoelomate

an animal that lacks a coelom, or body cavity or segments

simple diffusion

no gas exchange structure

Scolex

head of tapeworm

encysted

enclosed in a cyst

segmented worms

earthworms

chaetae

Bristle-like extensions found in some annelids used for locomotion

parapodia

unjointed appendages

Polychaetes

A class of annelids that have parapodia, ridgelike structures that help it move. The parapodia have numerous chaetae and can also function as gills.

Bivalves

have a hinged, two-part shell and include clams, oysters, and scallops.

Gastropods

snails and slugs

Chitons

Class Polyplacophora

Cephalopods

A member of a group of molluscs that include squids and octopus