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Parazoa – Phylum Porifera
Sponges
 Loosely organized and lack tissues
 Multicellular with several types of cells
 8,000 species mostly marine
 Adults sessile, larvae free-swimming
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Phylum
Porifera
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Radiata – Phyla Cnidaria and
Ctenophora
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Radial symmetry
Mostly marine
Only 2 embryonic germ layers – diploblastic
 Ectoderm
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and endoderm
Mesoglea connects 2 layers
Gastrovascular cavity for extracellular digestion
True nerve cells arranged in nerve net
 No
central control organ
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Phylum Cnidaria
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2 different body forms
polyp – tubular body with tentacles
surrounding opening (mouth and anus)
 Motile medusa – umbrella-shaped body with a
mouth on the underside surrounded by
tentacles
 Sessile
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Cnidocytes contain nemotocysts
 Hairlike trigger – cnidocil
 Some sticky while other sting
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Simple muscles and nerves
 Not
true muscles with mesoderm
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Phylum Platyhelminthes
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Flatworms
Lack a specialized respiratory or circulatory
system to transport gases
Bilaterally symmetrical with a head
First with 3 embryonic germ layers – triploblastic
Mesoderm key innovation – led to more
sophisticated organs
Acoelomate – lacking fluid-filled cavity
Some are important parasites
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Phylum Nematoda
Roundworms
 In nearly all habitats from poles to tropics
 Over 100,000 species
 Tough cuticle covers body
 Longitudinal but not circular muscles
 Pseudocoelom acts as hydrostatic
skeleton and circulatory system
 Complete digestive tract
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Phylum Rotifera
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Named for ciliated crown or corona
1800 species – mostly freshwater
Digestive tract with mouth and anus – mastax
Pseudocoelom
Reproduction unique
 Parthenogenesis
– amictic eggs – unfertilized diploid
eggs
 Mictic eggs –haploid eggs become males
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Phylum Mollusca
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Over 100,000 species
Soft body with, protective external shell*****
Body has 3 parts
 Foot,
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visceral mass and mantle
Eucoelomate
Open circulatory system
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Fiorito and Scotto’s Experiments Showed
Invertebrates Can Exhibit Sophisticated
Observational Learning Behavior
Octopuses trained to attack red or white ball
using reward and punishment
 Classical conditioning
 Color blind so must see relative brightness
of balls
 Observer octopuses watched trained
octopuses attack ball
 Observers learned faster than original
training
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Phylum Annelida
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Rings are distinct segments separated
by a septum
Segmentation has advantages
Repetition of components provides backup
2. Coelom acts as hydrostatic skeleton
3. Permits specialization
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Double transport system
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Circulatory system and coelomic fluid carries
nutrients, wastes and respiratory gases
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Digestive system complete and
unsegmented
 Sexual reproduction involves 2 individuals
(sometimes separate sexes other
hermaphroditic) with internal fertilization
 Asexual reproduction by fission
 15,000 species
 All annelids except leeches have setae on
each segment
 3 classes – Polychaeta, Oligochaeta and
Hirudinea
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Phylum Arthropoda
Perhaps most successful phylum
 ¾ of all described living species
 Success related to body plan of all major
biomes
 Exoskeleton made of chitin and protein
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 Can
be extremely tough or soft and flexible
 Relatively impermeable to water
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Segmented with appendages for
locomotion, food handling, or reproduction
 Tagmata – fused body segments
 Extensive cephalization
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 Well
developed organs for sight, touch, smell,
hearing and balance
 Compound eyes – ommatidia
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Sophisticated brain with 2 or 3 ganglia
connected to several smaller ventral nerve
ganglia
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Open circulatory system
 Gas exchange – gills, tracheal system with
spiracles or book lungs
 Complex digestive system
 Excretion – metanephridia or Malpighian
tubules
 6 main classes – Trilobita, Arachnida,
Diplopoda, Chilopoda, Insecta and
Crustacea
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Success of Arthropoda
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Exoskeleton
Regional Specialization
 Restriction
 Divergence
 Fusion
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Body
Appendages
Internal Anatomy
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Trilobita
 Extinct
early arthropods, bottom feeders, little
specialization of body segments
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Arachnida
 Spiders,
scorpions, ticks and mites
 2 tagmata- cephalothorax and abdomen
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Diplopoda – millipedes
2
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pairs of legs per segment, herbivorous
Chilopoda – centipedes
1
pair of legs per segment, carnivorous
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Insecta
 More
species of insects than all other animal
species combined
 Wings crucial to success – outgrowths of body
wall
 35 orders – differences in wings and
mouthparts
 Separate sexes with internal fertilization
 Metamorphosis
Complete – 4 stages with adult and larval stages
very different
 Incomplete – 3 stages with young resembling
miniature adults
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Crustacea
 Crabs,
lobsters, barnacles and shrimp
 Marine, fresh water and terrestrial
 Unique 2 pair of antennae
 Mandibles, maxillae and maxillipeds
 Swimmerets
 Cuticle covering head extends over
cephalothorax
 Nauplius larvae very different from adult
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Deuterostomia: Echinodermata
and Chordates
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Phylum Echinodermata
 Modified
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radial symmetry – 5 parts
Secondary – larvae are bilateral
 Cephalization
absent
 No brain – simple nervous system
 Endoskelton covered with spines and
pedicellariae
 Water vascular system with tube feet
functions in movement, gas exchange and
feeding
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Echinodermata
No excretory organs – respiration and
excretion by diffusion
 Autotomy – intentionally detach body part
that will later regenerate
 Reproduce sexually with separate sexes
 External fertilization
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Phylum Chordata
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4 key distinguishing innovations
Notochord – single flexible rod
Dorsal hollow nerve cord
Pharyngeal slits
Postanal tail
All chordates exhibit these at some time during
development
Subphylum Vertebrata – fish, birds,
amphibians, reptiles, mammals
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Phylum Chordata