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CoelomatesProtostomes
• Mouth develops from the blastopore
• Cleavage is spiral and determinate
• ALL HAVE A TRUE COELOM!
Mollusca• Bilateral symmetry• Open circulatory system• Soft bodied, with hard shell protection• Reduced or no segmentation• Radula; rasping tongue to sxrape food• True coelom• Many internal organs• Three body parts
– Foot– Visceral mass– Mantle
Four Classes• Polyplacophora
– Chitons– Cling to rocks– Live on rocky shores– Use muscular foot to grip
• Gastropods– Snails, slugs, nudibranchs– Largest class– Shell protects body– Torsion leads to twisted body– Uses radula to scrape algae and graze on
plants
• Bivalves:– Clams, oysters, mussels, scallops– Possess shell divided and hinged into two halves– Filter feeders– Sedentary lifestyle
• Cephalopods– Squid and octopus and nautilus– Use jaws to bite prey– Mouth as base of foot (foot drawn into several
tentacles)– Complex brains and capable of learning and
moving fast– Mantle reduced or absent– Can get large, How?
Annelids• SEGMENTATION!• Closed circulatory system• Alimentary canal• Five pairs of hearts• Gas exchange across skin• Metanephridia for gas exchange• Nitrogenous wastes exit from each segment
through pores• Nervous system with ganglia and ventral
nerve cords
Three classes:• Oligocheates
– Earthworms
• Polycheates:– Fanworms– Tube dwellers (marine)
• Hirudinea:– Leaches– Used to treat bruised tissues and to stimulate
circulation
Evolutionary trends in Annelids
• Coelom – serves as hydrostatic skeleton– Developed complex organ system– Protects internal structures
• Segmentation– Specialization of body segments
Arthropods
• Key characteristics:– Jointed appendages– Segmentation– Hard exoskeletons– Extensive cephalization– Open circulatory system– Gas exchange gills in water, book lungs or spiracles
on land
Success vs. Limitations
• Successes:– Exoskeleton, lets the thrive on land, but
limited– Jointed appendages allowed for walking
and then flying in some– More successful organization of segments
• Limits:– Exoskeleton is shed– Limited brain size– Limited body size
Subphyla• Trilobites
– Extinct group– Show pronounced segmentation, with little
variation in appendages– Early, primitive arthropods
• Chelicerates– Includes the arachnids– 1-2 body segments with 8 legs
• Uniramia– Includes insects, milipedes and centipedes
Classes
• Arachnids– Scorpions, spiders, mites
• Insects– 1pair of antennae– 6 legs– 3 body segments
• Crustaceans– Crabs, crayfish, lobsters, isopods (pill bugs)– 2 or 3 body segments
Deuterostomes
• Radial indeterminate cleavage
• Blastopore becomes the anus
Echinoderms
• Secondarily evolved radial symmetry
• Unique water vascular system
• Has mouth and anus
• Has endoskeleton
Classes
• Aseroidea– Sea stars
• Ophiuroidea– Brittle stars
• Echinoidea– Sea urchins and sand dollars
• Holothuroidea– Sea cucumbers
To what phylum does this organism belong?
Phylum Annelida
To what phylum does this organism belong?
Phylum Cnidaria
To what phylum does this organism belong?
Phylum Mollusca
To what phylum does this organism belong?
Phylum Echinodermata
To what phylum does this organism belong?
Phylum Arthropoda
To what phylum does this organism belong?
Phylum Nematoda
To what phylum does this organism belong?
Phylum Platyhelminthes
To what phylum does this organism belong?
Phylum Porifera
What evolutionary innovation both led to and limited the success of the
phylum to which this organism belongs?
. . . the exoskeleton
What type of symmetry does this organism exhibit?
. . . none
What evolutionary innovation does the phylum to which this organism
belongs have over Nematoda?
. . . segmentation
What is unique about the digestive system of this organism, and others
that belong to the same phylum?
. . . it is one way; having both a mouth and an anus
What two evolutionary innovations are common to the phylum to which
this organism belongs?
. . . bilateral symmetry and celphalization
What type of symmetry does this organism, and others belonging to
the same phylum, exhibit?
. . . radial symmetry
What evolutionary innovation is first exhibited by the phylum to which this
organism (a giant squid) belongs?
. . . the coelom
An open circulatory
system limits the size of these
animals
The closed circulatory system is
much more efficient!