protozoa phylum

single-celled heterotrophs

not technically considered an animal

"first animal" within Kingdom Protista

marine examples:

foraminifera

radiolarian

amoebas

porifera phylum

 "holes to bear"

most primitive true animal: sponges

have digestive cells instead of digestive system

are suspension feeders

suspension feeders

strain plankton and organic food particles from surrounding waters

cnidaria phylum

stinging "nettle"

jellyfish, sea anemones, and coral

cnidoblasts - large stinging cells

two forms: medusa (jellyfish) and polyp (sea anemones and coral)

worm phyla:

platyhelminthes phylum

"flat worm"

the simplest worm

worm phyla:

nematoda phylum

"thread"

first animal to possess a flow-through digestive system (anus and mouth)

worm phyla:

annelida phylum

"ring"

most advanced worm

metamerism - body divided into similar segments

polychaeta - class of marine worms

mollusca phylum

"soft-bodied"

second largest phylum following arthropoda

snails, squids, octopuses

squids - largeset invertebrates

octopuses - most intelligent invertebrates