Invertebrates
Asymmetry
Radial Symmetry (5 parts)
Bilateral Symmetry
Porifera
No Circulatory system
Cnidaria
Open Circulatory System
no circulatory system, nerve cells, or tissues
many are hermaphrodites
filter feeders
sessile
Example : Sponges
Echinodermata
Open Circulatory System
Closed Circulatory System
Arthropoda
Annelida
Mollusca
No Traditional Circulatory System
Platyhelminthes
Medusa : free swimming, tentacles down
Polyp : sessile, tentacles up
Cnidocytes - cells that contain stinging poisonous barbs with which they paralyze prey
Jellyfish
Coral
Hydra
Sea Anemone
Examples
marine ecosystems
water vascular system
tube feet (suction cups)
Unique Characteristics : exoskeleton (molting), jointed appendages, segmentation
Centipedes
Millipedes
Crustaceans
Arachnids
Insects
two body regions (cephalothorax and abdomen)
gills
large claws
4 pairs of walking legs
Examples
primitive
segmentation
class Chilopoda
one pair of legs per segment
primitive
segmentation
class Diplopodia
2 legs per segment
3 body regions
metamorphosis
2 body regions
no antennae
Examples
segmentation
earthworms are hermaphroditic while others are 2 separate sexes
important to soil
complete digestive track
Examples
cephalization
hermaphroditic
many parasites
Examples
Gastropods (stomach footed)
Cephalopods (head footed)
Unique Characteristics
univalves
bivalves
snails
clams
oysters
mussels
scallops
abalone
conch
octopus
squid
most have separate sexes, some hermaphroditic
true coelom (body cavity)
muscular foot
gills or lungs in mantle cavity
visceral mass : contains most organs
mantle : soft outer layer of body
flatworms
tapeworms
flukes
segmented worms
earthworms
leeches
spiders
ticks
mites
lobster
crayfish
shrimp
Examples
bees
butterflies
sea urchins
sand dollars
starfish
EXCEPTION : larvae are bilaterally symmetrical
