Invertebrate Diversity II
The coeomate protostomes:
Ph. Mollusca
Ph. Annelida
Ph. Arthropoda
Body Cavities
schizocoely
enterocoely
Q1: Pseudocoelous animals lack
1)
2)
3)
4)
Body symmetry
A body cavity
A mesodermal cavity lining
True tissues
Two kinds of coelomates
• Protostomes vs. Deuterostomes
• Distinguished by their patterns of
embryonic development
• (Note: developmental patterns are highly
conservative, evolutionarily, but may reflect
convergent evolution)
Protostomes vs. Deuterostomes
• Protostome
phyla:
• Deuterostome
phyla:
– Mollusca
– Annelida
– Arthropoda
– Echinodermata
– Chordata
Ph. Mollusca: mollusks
• 2nd largest phylum in the Animal kingdom
• (e.g., there are more species of terrestrial
mollusks than there are vertebrates!)
• Body plan -- 3 regions:
– ventral muscular foot
– visceral mass
– mantle -- surrounds internal organs
• Radula
• Torsion
Basic body plan of mollusks
The radula
• Only in mollusks
• Chitinous mouthparts
4 Classes of Mollusks
• Cl Polyplacophora -- chitons
• Cl. Gastropoda -- snails, slugs, nudibranchs
• Cl. Bivalvia -- clams, mussels, oysters . . .
• Cl. Cephalopoda -- octopus, squid, cttlefish,
nautilus, etc.
Cl. Polyplacophora: chitons
Lined chiton -- 8 dorsal plates; scrapes algae off rocks
Gumboot chiton
Cl. Gastropoda
Nudibranchs – marine species –
shell-less snails
Cl. Bivalvia: the bivalves
• 2 valves -- shells
• filter feeders
Q2: Mollusks are
1)
2)
3)
4)
Segmented
Deuterostomes
Pseudocoelomate
Schizocoelous
Q3: The group of modern mollusks which
most closely resembles the ancestral form is
1)
2)
3)
4)
Polyplacophora
Gastropoda
Bivalvia
Cephalopoda
Cl. Cephalopoda
•
•
•
•
•
•
Squid, octopus, nautilus, cuttlefish
Nautilus – external shell
Cuttlefish – internal shell (the “cuttlebone”)
Others have lost shells, evolutionarily
Excellent vision, big brains (for inverts!)
Good at predicting soccer matches
Pacific Giant Octopus
9 foot giant squid (and beak)
Cuttlefish and Nautilus
Q4: “Cephalopod” means literally
1)
2)
3)
4)
Ten-legged
Head-foot
Stomach-foot
Mantle shell
Ph. Annelida
•
•
•
•
Segmented worms
Most have septa between segments
Allows for controlled movement
3 classes:
– Cl. Polychaeta -- polychaetes
– Cl. Oligochaeta -- earthworms
– Cl. Hirudinea -- leeches
Q5: Annelids are:
1)
2)
3)
4)
Deuterostomes
Schizocoelous
Radially symmetrical
Triploblastic
Cl. Polychaeta
Feather
Duster
Worm
Cl. Oligochaeta
Cl. Hirudinea (leeches)
Q6: Marine annelids belong to Class
1)
2)
3)
4)
Hirudinea
Polyplacophora
Scyphozoa
Polychaeta
P. Arthropoda: Arthropods
• Most species rich phylum on earth!
• segmented bodies, but segments fused
into tagmata (functional units): head,
thorax, abdomen
• exoskeleton of chitin
• jointed appendages: “Arthro-” + “pod”
Q7: Traditional phylogeny regards
annelids and arthropods as being closely
related because both phyla
1)
2)
3)
4)
Have determinate, spiral cleavage
Are schizocoelous protostomes
Are segmented with ventral, solid nerve chords
All of the above
3 sub-phyla in Arthropoda:
• Sub-Ph. Chelicerata - - horseshoe crabs,
spiders, mites, scorpions
• Sub-Ph. Crustacea: crustaceans
• Sub-Ph Uniramia: insects, millipedes,
centipedes
Sub-phyla of Arthropods
• Do they have chelicerae? (pincers/fangs)
– Sub-ph. Chelicerata -- also no antennae
• Or do they have mandibles? (jaws)
– Sub-ph. Crustacea
• 2 pair antennae; legs biramous
– Sub-ph Uniramia
• 1 pair antennae; legs uniramous
Chelicerae vs. Mandibles
Chelicerae
Mandibles
Arthropod Appendages
Biramous
Uniramous
Chelicerates
Limulus
Argiope
Dust Mite
Scorpion
Wood Tick
Crustaceans
Q8: Horseshoe crabs are grouped with
spiders rather than true crabs because
horseshoe crabs have
1)
2)
3)
4)
chelicera
eight legs
gills
antennae
3 classes in Uniramia
• Cl .Chilopoda (centipedes)
• Cl. Diplopoda (millipedes)
• Cl. Insecta (insects)
Centipede (Cl. Chilopoda)
Millipede (Cl. Diplopoda)
Class Insecta
Q9: The most speciose class of animals on
earth is
1)
2)
3)
4)
Insecta
Crustacea
Bivalvia
Oligochaeta
Q10: Insects differ from annelids in having
1)
2)
3)
4)
A cephalized nervous system
A segmented body plan
An open circulatory system
A pseudocoelom