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Chapter 33
The AncestorsProtists: Choanoflagellates
The AncestorsColonies of choanoflagellates
The AncestorsColonies of choanoflagellates
Porifera – The Sponges
Porifera – The Sponges
Sessile filter feederGrouped based on
“skeleton” type.Can form
gemmules for protection.
Porifera – The Sponges
AsymmetricalNo tissue layers.
Porifera – The SpongesSexual
reproduction - hermaphrodites
Can grow whole new sponges if cut in pieces
CnidariaExamples: jellyfish, anemones, hydra and
coral
CnidariaNamed for cnidocytes
CnidariaDiploblasticTwo body forms: polyp & medusaGrouped based on amount of life spent as
polyp or medusa
Cnidaria
Reproduces asexually by budding.
Cnidaria
Platyhelminthes - FlatwormsExamples: planaria, liver flukes, tapeworms
Platyhelminthes - Flatworms
Most are parasitic
Platyhelminthes - Flatworms
Bilateral symmetry
Simplest phylum with a head
Simple organ systems
Reproduce sexually and asexually
Platyhelminthes - FlatwormsAcoelomatesTriploblastic
RotiferaNamed for feeding rotorsPseudocoelomatesHave an anus!
Images from http://www.microscopy-uk.org.uk
RotiferaUsually reproduces by parthenogenesis
Nematoda – RoundwormsFound in most aquatic habitats, soil, and in
plant and animal tissues
Nematoda – RoundwormsMany are parasitic – hookworms,
roundworms, pin worms, heartworms, etc.
Nematoda – RoundwormsPseudocoelomates
Simple organs
Annelida – Segmented WormsExamples: earthworms, fireworms, leeches
Annelida – Segmented Worms“Little rings” –repeating segments, some
specializedCoelomates
SetaeParapodia
Annelida – Segmented WormsFairly complex anatomy
MolluscaLargest classes:
GastropodsBivalvesCephalopods
MolluscaMuscular foot
MolluscaHead
MolluscaVisceral mass
Arthropoda“Jointed foot”
ArthropodaMost successful animal phyla – 67% of all
species!
ArthropodaFour main groups:
CheliceriformsMyriapodsHexapodsCrustaceans
ArthropodaExoskeleton - ecdysis
ArthropodaOpen circulatory system
ArthropodaTracheal tubesSpiracles vs. book lungs
ArthropodaMalpighian tubules
Echinodermata“Spiny skin”
EchinodermataRadial symmetry
EchinodermataWater vascular systemTube feet
EchinodermataNo head or brainSimple anatomyDeuterostomesEndoskeleton
