Organizing Animal Phyla
Turn in the ocean acidification reading
assignment, and locate your mollusk
notes outline
Mollusk quiz
• 15 minutes MAX!
TEST: TUESDAY 4.27
• TOPICS:
– Annelids
– Arthropods
– Dichotomous keys
– Mollusks
– Echinodermata*
– “Big 9” Phyla*
Simple Invertebrates
• Some time ago, we studied the simple
invertebrates:
Common
Name
Porifora
Cnidaria
PlatyNematoda
helminthes
Sponges
Jellyfish
Flatworms
Radial
diploblasts
Triploblastic Through gut
bilaterans
Key
No
Characteristic tissues
/ Innovation
Roundworms
• These animals all lack respiratory or circulatory
organs, which is why we describe them as “simple.”
Complex Invertebrates
• Lately, we have studied invertebrate animals
that have circulatory systems, respiratory
systems, or both:
Common Name
Mollusca
Annelida
Arthropoda
Mollusks
Segmented Worms
Arthropods
Segmented,
softbodied
Closed
exoskeleton
Key Characteristic / Mantle and CaCO3
innovation
shell
Circulatory System
Open
Open
Respiratory System
gills
Diffusion / skin
Gills or book lungs
Important Classes
Cephalopods,
Gastropods,
Bivalves
n/a (several)
Crustacea, Insecta,
Arachnida,
Myriapoda
Two Phyla Left
• Phylum Echinodermata includes the starfish, and is
our next topic.
• Phylum Cordata includes everything with a
backbone, and will be a separate unit. It includes
– Mammals, Birds, Reptiles, Fish, Amphibians
A quick introduction to the Echinodermata
• Includes starfish, sea urchins,
sand dollars, and others.
• Name means “spiny skin”
• Important to marine
ecosystems (only major
phylum which includes NO
species that live on land or in
fresh water)
Some Key Characteristics
• Calcitic, mesodermal endoskeleton.
(translation: Many tiny calcium-based bones
in their skin)
• Pentaradial symmetry.
• Water-based vascular system
Organizing the Phyla
• Kingdom Animalia can be divided into several
Subkingdoms or Superphyla – cladistic
groups between a kingdom and a phylum
• Kingdom>Subkingdom>Superphylum>Phylum
>Subphylum>Superclass>Class… etc. etc.
Subkingdoms Metazoa and Parazoa
• The subkingdom Metazoa (“upper
animals”)includes all animals that have tissues
that carry out different functions.
• The subkingdom Parazoa (“beside the
animals”) includes Phylum Porifora and a few
other minor phyla (remember – we’re only
looking at the “big 9” animal phyla)
Superphyla Radiata and Bilatera
• The subkingdom metazoa is further divided
into 2 superphyla: Radiata and Bilaterata,
based on body symmetry.
• Echinoderms are in superphylum bilaterata
even though they are pentaradial
– Evolved from bilaterans
– Have bilateral larval stage
Protostomes vs Deuterostomes
• Protostomes and
deuterostomes are
two groups of animals
(superphyla to be
specific) organized by
the following:
– Protostomes have
ventral nerve cords,
Deuterostomes have
dorsal nerve cords
– Embryological
development is
different:
Word Meanings
• Protostome: “first mouth”
• Deuterostome: “second mouth”
The big ideas
• Phylum echinodermata includes starfish and
other organisms that are very distinct from
other invertebrates
• Subkingdoms Parazoa vs. Metazoa
• Superphyla Radiata vs. Bilaterata
• Superphyla Protostomata vs. Deuterostomata
• Enchinoderms are more closely related to
chordates than any other invertebrates.