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7/1/19
1
Origin of Animals • Cambrian radiation • Animal body plans
– Symmetry – Tissue systems – Development
• Porifera (Sponges) • Cnidaria (Jellies)
– True tissues – Radial symmetry
• Protostomes – Lophotrochozoa
• Molluscs • Annelids • Plus other groups we’ll skip
– Ecdysozoa (tomorrow) July 1, 2019
Brief History of Life
Eukaryotes Diplomonads
Parabasalids
Euglenozoans
Stramenopiles
Alveolates
Rhizarians
algae G
reen
Am
oebozoans Opisthokonts
Excavata
Diatoms
Golden algae
Brown algae
Dinoflagellates SAR
Apicomplexans
Ciliates
Radiolarians
Forams
Cercozoans
Red algae
Chlorophytes
Charophytes
Plants
Slime molds
Tubulinids
Entamoebas
Nucleariids
Fungi
Choanoflagellates
Animals
Unikonta
Archaeplastida
Ch 31
Ch 32-34
Unikonts è
General characteristics of animals:
– Multicellular
– Heterotrophic
– Internal digestion
– Motile
But there are exceptions to each of these�.
The Burgess Shale fossil bed Hallucinigenia
Distinct Body Plans Evolved among the Animals
Look at: – Symmetry – Body cavity (coelom) structure – Segmentation – External appendages
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Radial symmetry
Bilateral symmetry
Symmetry
Most animals have a central body cavity (Coelom)
Coelom Body covering (from ectoderm)
Digestive tract (from endoderm)
Tissue layer lining coelom and suspending internal organs (from mesoderm)
(a) Coelomate
Body covering (from ectoderm)
Pseudocoelom
Digestive tract (from endoderm)
Muscle layer (from mesoderm)
(b) Pseudocoelomate
Body covering (from ectoderm) Tissue-
filled region (from mesoderm)
Wall of digestive cavity (from endoderm)
(c) Acoelomate
Three tissue layers: • Endoderm • Mesoderm • Ectoderm
Fig. 32-9
Protostome Deuterostome
Eight-cell stage Eight-cell stage
Spiral and determinate Radial and indeterminate Coelom
Archenteron
(a) Cleavage
(b) Coelom formation
Coelom
Key Ectoderm Mesoderm Endoderm
Blastopore Blastopore Solid masses of mesoderm split and form coelom. Folds of archenteron
form coelom. Anus Mouth
Digestive tube
Mouth Anus Mouth develops from blastopore. Anus develops from blastopore.
(c) Fate of the blastopore
Segmentation
Animals Porifera Metazoa
ANCESTRAL PROTIST
Ctenophora Eumetazoa
Deuterostom
ia
Bilateria
Lophotrochozoa Ecdysozoa
Cnidaria
Acoela
Hemichordata
Echinodermata
Chordata
Platyhelminthes
Syndermata
Ectoprocta
Brachiopoda
Mollusca
Annelida
Nematoda
Arthropoda
Sponges
Cnidarians
Echinoderms
Chordates
Brachiopods
Annelids
Molluscs
Arthropods
Ediacaran Cambrian PROTEROZOIC PALEOZOIC
Time (millions of years ago) 635 605 575 545 515 485 0
We will concentrate on these seven phyla
Where are humans in this
tree?
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Is this your ancestor?
• Colonial Choanoflagellates are the sister group to all other animals
These are protists Not fully multicellular organisms
OTHER EUKARYOTES
Choanoflagellates
Sponges
Other animals
Anim
als
Individual choanoflagellate
Collar cell (choanocyte)
Simple Animal Phylogeny
Sponges Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia
Eum
etazoa Sponges
Link to video
For each major group, think about:
• A familiar example • What is the general body plan?
– i.e. What kind of symmetry? Does it have a Head? Tissue layers? Body cavity? Legs?
• How does it eat? • How does it move? • How does it reproduce?
Sponge Life cycle
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Animal Phylogeny Figure 33.UN02
Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia
Eum
etazoa
Diversity among Cnidarians Cnidarians have two body types
Mouth/anus
Gastrovascular cavity
Mouth/anus
Medusa Polyp
Body stalk
Two tissue layers
Simple nerve net
A typical Cnidaria Life Cycle Medusa
Polyp
Animal Phylogeny
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Protostomes
• Bilaterally symmetrical • Anterior brain that surrounds entrance
to digestive tract • Ventral nervous system with paired or
fused longitudinal nerve cords
Figure 33.UN03
Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia
Bilateria
Mollusca Annelida
A flatworm
Gastrovascular cavity
Mouth
Eyespots Ventral nerve cords
Ganglia
Lophophore
Trochophore
Figure 33.17
(a) A land snail
(b) A sea slug (nudibranch)
Basic body plan of a mollusk Nephridium
Visceral mass Heart
Coelom
Mantle Mantle cavity
Anus
Gill
Gonads
Heart
Intestine
Stomach Shell
Radula
Mouth Esophagus Nerve
cords Foot
Digestive tract
Mouth
Radula
Video
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Figure 33.20
Mantle Hinge area
Digestive gland
Mouth
Shell
Palp Foot
Mantle cavity Gonad Gill
Incurrent siphon
Water flow
Excurrent siphon
Anus
Adductor muscle (one or two)
Gut Coelom
Heart
Annelida Epidermis Cuticle
Chaetae
Intestine
Fused nerve cords
Clitellum
Crop
Metanephridium
Coelom
Anus
Skin
Intestine
Gizzard
Ventral nerve cords with segmental ganglia Circulatory
system vessels Mouth
Cerebral ganglia
Giant Australian earthworm
Earthworm reproduction
Link to video