Kingdom Animalia: The Metazoa

•  Kingdom Animalia: Metazoa I
– Most Diverse group > one million species
– Active, Mobile Predators (mostly)
– Characters of the Animalia / Metazoa:
Kingdom
Animalia:
The Metazoa
•  Multicellular, Diploid
•  Heterotrophic Ingestors (except Porifera)
•  Lack Cell Walls (ancestral)
•  Structural Proteins (e.g. collagen)
•  Intercellular Junctions
•  Multicellular Embryo
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•  Examples of the Animalia: Metazoa
•  Kingdom Animalia: Metazoa II
– The Parazoa (nearly animals) - sponges; and
– The Eumetazoa - ‘True’ animals (most)
•  Characters of the Eumetazoa
– Embryology: Blastula -> Gastrula
– Gastrulation creates Gut & True Tissues
– Nervous & Muscle tissues (in most)
•  Most Animal Phyla are Marine
•  Many ancestral traits
–  Lack True tissues, only specialized cells
–  Lack a Gut, intracellular digestion only
–  Eumetazoa: ‘True’ Animals - all others
•  Radiata: P. Cnidaria - jellies & corals
–  Radial symmetry, simple guts, limited nervous system
•  Bilateria: All other Eumetazoa
–  worms, snails, crabs, stars, fishes, you and me
–  Complete gut (in most), true muscle & nerve tissues
–  Cephalization
– Only a few groups invaded land
Animalia Phylogeny:
Points of Agreement
Alternate Views of the
Bilateria
PARAZOA
EUMETAZOA
‘Radiata’
P. Porifera
–  Parazoa: P. Porifera - sponges
P. Cnidaria
BILATERIA
P. Ctenophora
Deuterostomia
Protostomia
Deuterostomia
Ecdysozoa
Lophotrochozoa
7. Triploblastic: Three Germ Layers
Endoderm, Ectoderm & Mesooderm
8. Muscle and Nervous Tissues
9. Bilateral Symmetry
10. Cephalization
Radial
Symmetry?
4. Gastrulation
5. Gut
6. Diploblastic: Two Germ Layers
Endoderm & Ectoderm
1. 
Multicellularity: Diploid
2. 
Hox Genes
3. 
Embryonic Development
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K. Animalia: The Metazoa
PARAZOA
EUMETAZOA
‘Radiata’
P. Porifera
P. Cnidaria
BILATERIA
DEUTEROSTOMIA
PROTOSTOMIA - OR
P. Ctenophora
Lophotrochoza / Ecdysozoa
•  K. Animalia: Metazoa
– Parazoa:
– P. Porifera (pore-bearers) - sponges
• Many ancestral traits
Radial
Symmetry?
7. Triploblastic: Three Germ Layers
Endoderm, Ectoderm & Mesooderm
8. Muscle and Nervous Tissues
9. Bilateral Symmetry
10. Cephalization
4. Gastrulation
5. Gut
6. Diploblastic: Two Germ Layers
Endoderm & Ectoderm
1. 
Multicellularity: Diploid
2. 
Hox Genes
3. 
Embryonic Development
•  P. Porifera: 5,000-10,000 spp, mostly marine
– Feeding cells: choanocytes / collar cells
– Suspension feeders: filter feeders
– Spicules: skeletal material of
•  protein, silica, or calcium carbonate - CaCO3
– Asexual & Sexual reproduction
– Planktonic larvae (in many)
– Metamorphosis of larva to adult form upon
settlement/recruitment
•  K. Animalia: Metazoa; Eumetazoa
• Radiata: P. Cnidaria & P. Ctenophora
– Radial symmetry
– Simple gut - Gastrovascular cavity
– Limited nervous system - nerve nets
– Diploblastic (two embryonic tissues)
– Lack True Tissues, only specialized cells
– Lack a Gut, intracellular digestion only
• Derived traits:
– True multicellularity -> Specialization
– Multicellular embryo
•  Examples of the Animalia: Metazoa
–  Parazoa: P. Porifera - sponges
–  Eumetazoa: ‘True’ Animals - all others
Derived traits:
•  Gut! Extracellular digestion
•  True tissues
•  Radiata: P. Cnidaria & P. Ctenophora
–  Radial symmetry, simple guts, limited nervous system
–  Diploblastic, two embryonic tissues: ectoderm & endoderm
•  Bilateria: All other Eumetazoa - most animals
–  worms, snails, crabs, stars, fishes, you and me
–  Bilateral Symmetry, Triploblastic, better Gut & Head
•  P. Cnidaria (Coelenterata):
– Medusas & Polyps
– Cnidocytes with Nematocysts
– Two tissues: Epidermis & Gastrodermis
– Mesoglea is the jelly between
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Figure 7.07
•  Eumetazoa:
Radiata: P. Cnidaria (Coelenterata):
•  9,000 Species in 4 Classes
•  Hydrozoa: polyps, medusa, & complex life histories
–  Stingers! Hydra, Obelia & Fire coral
–  Portuguese man-of-war: Physalia physalis
•  Scyphozoa: large medusae, Aurelia (small polyps)
•  Cubozoa: cubomedusae (strong toxin)
•  Anthozoa: polyps only; many with zooxanthellae
Class Hydrozoa
-  small polps (many)
-  often colonial
-  some with complex
life styles
-  a few with large,
complex medusae
-  many ‘stingers’
–  Stony corals: Acropora, Porites
–  Anemones: Anthopleura
–  Sea fans, sea whips, sea pens, gorgonians
Figure 7.09
Fire coral - Hydrozoa
Class Scyphozoa:
-  includes most larger medusae
-  polps are small and ‘split’ off
-  Aurelia
Class Anthozoa - polyps only
- reef-building corals, anemones, etc.
- many have Zooxanthellae
P. Ctenophora - comb jellies
•  Radial Symmetry - ‘Radiata’
•  Bands of Cilia; tentacles, but no cnidocyts
•  Examples of the Animalia: Metazoa
–  Parazoa: P. Porifera - sponges
–  Eumetazoa: ‘True’ Animals - all others
•  Guts & True tissues
•  Radiata: P. Cnidaria & P. Ctenophora
–  Radial symmetry, simple guts, tissues
–  Diploblastic: endoderm & ectoderm
•  Bilateria: All other Eumetazoa
–  worms, snails, crabs, stars, fishes, you and me
–  Bilateral Symmetry
–  Triploblastic: three embryonic tissues - Mesoderm
–  Complete gut (in most), true muscle & nerve tissues
–  Cephalization
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Eumetazoa:Bilateria: worms, snails, crabs, fish, etc
Eumetazoa:Bilateria: worms, snails, crabs, fish, etc
– Bilateral Symmetry
– Complete gut (most), true muscle & nerve tissues
– Triploblastic (three embryonic tissues)
•  Protostomia: first hole (blastopore) becomes mouth
•  Ectoderm, Endoderm, Mesoderm - muscle
– Cephalization
–  Several phyla of worms
–  P. Mollusca
–  P. Arthropoda: Crustacea
–  Lophophorates: three phyla
•  Deuterostomia: second hole becomes mouth
–  P. Echinodermata, Hemichordata & Chordata
•  P. Platyhelminthes - flatworms 20,000 species
–  Incomplete gut = gastrovascular cavity
–  Muscle (from mesoderm)
–  Bilateral symmetry with a head - learning!
–  Free-living predators: Turbellarians, and
–  Parasites: Flukes, Trematodes &
Cestodes/tapeworms - to 15 meters (50’)
•  Complex life histories (multiple hosts)
•  P. Nematoda - round worms 10,000-25,000+ spp
–  Complete gut
–  Circulatory system
–  Chitonous exoskeleton
–  Pseudocoelom
–  Hydrostatic skeleton
•  Free-living & Diverse parasites:
–  Parasitize plants, insects, humans, etc.
Ecdysozoa: P.
Nematoda
•  P. Nematoda: nematodes are nonsegmented
pseudocoelomates covered by a tough cuticle
•  Among the most widespread of all animals,
nematodes, or roundworms
–  Occur free-living in soil and aquatic habitats
–  And as parasites in moist tissues of plants, & in the
body fluids and tissues of animals
–  As parasites of animals and plants, they may be the
most speciose of all groups!
•  P. Annelida - segmented worms 20,000 species
–  Repeated units = segments -> Specialization
–  True coelom (lined with mesoderm)
–  Closed circulatory system, many with gills
–  Trochophore larvae
–  Three groups: marine annelids mostly
–  C. Polychaeta: most specialized & speciose
•  Roaming predators - Nereis
•  Suspension feeders - tube worms
•  Deposit feeders - lug worms
•  Palolo worms & Epitokes
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•  Lophotrochozoans often share one of two common
characteristics:
–  a lophophore (feeding structure)
–  a trochophore larva (development stage)
•  Marine annelids and marine molluscs have
Trochophore larvae
- common ancestry?
•  P. Mollusca - snails, clams, squid, etc.
Most Diverse group of marine organisms: 1-200,000 spp
–  Soft bodied, with Calcium Carbonate shell(s)
–  Mantle & Mantle Cavity
–  Muscular foot
–  Radula - rasping ‘tongue’
–  Well developed organ systems
–  Trochophore Larvae
–  Several classes
Figure 7.21a
•  P. Mollusca
– C. Polyplacophora - chitons: 8 plates, herbivorous
– C. Gastropoda - stomach-foot: most diverse
snails, slugs, nudibranchs
•  Torsion
•  Herbivores & Active Predators
– C. Bivalvia - two-valves (shells): filter feeders,
clams, oysters, mussels
– C. Cephalopoda - head-foot, large, intelligent
predators: nautiloids, cuttlefish, squid, octopus
Many Gastropods are Herbivores:
Megathura - keyhole limpet; Haliotis – abalone
Gastropods are also predators & parasites:
•  The radula of Conus snails are modified as poisoned harpoons;
•  Other snails suck blood as parasites, Cancelleria cooperi
Nudibranchs - Sea Slugs, lost their shells
•  The gills of nudibranchs are ‘naked’, but often
•  Protected by the food they eat, e.g. hydroid nematocysts
–  Other classes - tuskshells, monoplacophorans
Mollusca: Bivalvia
•  Molluscs of class Bivalvia
–  Include clams, oysters, mussels, and scallops
–  Have a shell divided into two halves
•  Oysters attach one of their shells to the substrate Pinctada
•  Mussels attach more flexibly to the bottom with
byssal threads •  Mytilus
•  Pearls are made from the mantle when it is
irritated by sand or other particles
Cephalopods
•  Class Cephalopoda includes nautiloids, cuttlefish,
squids and octopuses
–  Carnivores with beak-like jaws
–  Their muscular foot evolved into arms and tentacles
with suckers to capture prey
–  Chambers filled with gas allowed their ancestors to
leave the bottom and evolve into active, swimming
predators
–  Most living cephalopods have much-reduced shells
–  Large, Intelligent Predators
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•  P. Arthropoda - most diverse phylum of life!
•  Over 1 million species
–  Segmented with great specialization
–  Jointed limbs - with diverse function
–  Exoskeleton of chitin (ecdysis)
–  Many groups primarily Terrestrial or Freshwater:
P. Arthropoda
Subphylum (or Class) Crustacea - primarily marine
–  Copepoda: make up most of the zooplankton
–  Amphipoda: laterally compressed
–  Isopoda: dorsoventrally flattened
–  Cirripedia = barnacles: sessile, calcium carbonate plates
•  Rhizocephalan parasites
e.g. Insects, spiders, centipedes, etc.
–  Subphylum Crustacea - primarily Marine
–  Euphasiids: Krill - large zooplankton
–  Decapoda: 10 walking legs
•  Shrimp, Lobster, Crabs, Hermit crabs
–  Planktonic larvae (most), molting & metamorphisis
P. Arthropoda:
Subphylum Crustacea
•  Euphasiidae - krill, shrimp-like zooplankton
–  Primary food of many baleen whales & others
Figure 7.27
A molt of Grapsus grapsus - a common shore crab
-  To grow, arthropods must periodically shed their exoskeleton
and replace it with a new, larger exoskeleton
‘Ecdysis’ refers to the period (time) and act of molting
Hermit crabs are not ‘true’ crabs
- their abdomen is not protected by a hard shell
- they use the shells of others for their ‘home’
Krill at the surface on a cloudy day
Whales fed at the surface, Quebec
P. Arthropoda:
Subphylum
Cheliceriformes
•  Few other arthropods are marine, mostly in the
•  Chelicerata: Horseshoe crabs - Limulus are
reminiscent of ancestral arthropods
•  Examples of the Animalia:
–  Parazoa: P. Porifera - sponges
•  Many ancestral traits
–  Lack True tissues, only specialized cells
–  Lack a Gut, intracellular digestion only
–  Eumetazoa: All other Animals
•  Radiata: P. Cnidaria - jellies & corals
–  Radial symmetry, simple guts, limited nervous system
•  Bilateria: All other Eumetazoa
–  worms, snails, crabs, stars, fishes, you and me
–  Complete gut (in most), true muscle & nerve tissues
–  Cephalization
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•  Bilateria: Protostomia
Lophophorates:
•  Animalia: Metazoa
–  Eumetazoa: Bilateria
•  worms, snails, crabs, stars, fishes, you and me
•  Bilateral Symmetry & Cephalization
•  Complete gut (in most), true muscle & nerve tissues
•  Triploblastic (three embryonic tissues)
Lophophore: A ciliated feeding structure for Filter Feeding
U-shaped guts
Three groups (Phyla)
-  Bryozoa (moss animals) or Ectoprocta: abundant
-  Phoronida: parchment worms, few species
-  Brachiopoda: lamp shells, once abundant (Paleozoic)
–  Protostomia: first hole (blastopore) becomes mouth
•  Several phyla of worms, etc.
•  P. Mollusca, P. Arthropoda - Crustacea, & Lophophorates
–  Deuterostomia: second hole (blastopore) becomes mouth
-  Dorsal and ventral shells
•  P. Echinodermata
•  P. Hemichordata
•  P. Chordata
P. Echinodermata (spiny skin) 6,000-7,000 spp
•  C. Asteroidea: sea stars
•  C. Ophiuroidea: brittle stars
•  C. Echinoidea: sea urchins, sand dollars
•  C. Holothuroidea: sea cucumbers
•  C. Crinoidea: sea lilies
Animalia: Bilateria: Deuterostomia
•  P. Echinodermata (spiny skin) 6,000-7,000 spp
•  Endoskeleton: calcium carbonate plates & spines
•  Secondary, pentamerous radial symmetry
•  Water vascular system: madreporite - tubefeet
Animalia: Bilateria: Deuterostomia
P. Chordata:
•  Notochord: a stiffened rod
•  Dorsal, hollow nerve cord
•  Pharyngeal (gill) slits
•  Post-anal tail
Animalia: Bilateria: Deuterostomia
P. Chordata:
•  Subphylum: Urochordata (tailed chodates)
–  Tunicates, salps, larvaceans
• 
Subphylum: Cephalochordata (head chordates)
–  Lancelets
• 
Subphylum: Vertebrata/Craniata
–  The vertebrates (backbone/skull)
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