1. An Introduction to Animals

2. Chapter 30 Opening Roadmap.
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3. What Is an Animal? Animals are eukaryotes that share key traits:
Multicellularity, with cells that
Lack cell walls
Have an extensive extracellular matrix
Heterotrophy
They obtain necessary carbon compounds from other organisms
Most ingest their food rather than absorbing it
Motility
They move under their own power at some point in their life cycle

4. Protists in an older taxonomic “kingdom”
Figure 30.1
Bacteria
Archaea
About 3.5 billion years ago!!
Amoebozoa
OPISTHOKONTA
Sister Kingdom to Animalia
Fungi
Choanoflagellates
From flagellated protists
Animals
Only 0.5 million years ago!
EUKARYOTES
Excavata
Algae
Figure 30.1 Choanoflagellates Are the Closest Living Relatives to Animals.
Land plants
Rhizaria
Protists in an older taxonomic “kingdom”
Alveolata
Stramenopila
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5. These have more or less radial symmetry
Table
Biologists have described about 1.5 million species in 30–35 phyla (major lineages) of animals—the exact number is estimated to be much larger.
These have more or less radial symmetry
These develop their embryonic mouth before their anus
Table An Overview of Major Animal Phyla.
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6. Largest phylum! More than all the other animals combined!
Table
Largest phylum! More than all the other animals combined!
These develop their embryonic mouth after their anus, i.e. second!
Table An Overview of Major Animal Phyla.
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7. What Key Innovations Occurred during the Origin of Animal Phyla?
Biologists consider several types of data:
Fossils
Comparative morphology
Comparative development (evolutionary developmental biology, or evo-devo)
Comparative genomics

8. Animalia is a clade (monophyletic), a natural (legitimate) taxon
Figure 30.2
Choanoflagellates
ANIMALIA
Fungi
Porifera
Choanoflagellates
(sponges)
ANIMALIA
Here we are seeing the kingdom divided into some of the 30-some phyla (major groupings)
Multicellularity
Ctenophora
(comb jellies)
Cnidaria
(jellyfish, corals,
sea anemones)
LOPHOTROCHOZOA
Diploblasty
Rotifera
(rotifers)
Loss of
coelom
Animalia is a clade (monophyletic), a natural (legitimate) taxon
Platyhelminthes
(flatworms)
Segmentation
Annelida
(segmented worms)
PROTOSTOMES
Mollusca
BILATERIA
(snails, clams,
squid)
Figure 30.2 A Phylogeny of Major Animal Phyla Based on DNA Sequence Data.
ECDYSOZOA
Nematoda
(roundworms)
Bilateral symmetry
Triploblasty
Cephalization
Coelom?
Arthropoda
Segmentation
(insects, spiders, crustaceans)
DEUTEROSTOMES
DEUTEROSTOMES
Radial symmetry
Echinodermata
(in adults)
(sea stars,
sand dollars)
Chordata
Segmentation
(vertebrates, tunicates)
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9. Morphological Evidence for the Sponges-First Hypothesis
Sponges share characteristics with choanoflagellates
Both are benthic (live at bottom of aquatic environments)
Both are sessile (adults live permanently attached to a substrate rather than moving freely)
Both feed using cells with nearly identical morphology
Beating flagella of choanoflagellates and specialized cells in sponges called choanocytes trap organic debris
Feeding occurs at the cellular level

10. Sponges share characteristics with choanoflagellates
Figure 30.3
Sponges share characteristics with choanoflagellates
(a) Choanoflagellates are sessile protists; some are colonial.
(b) Sponges are multicellular, sessile animals.
Colony
Multicellular
organism
(cross section)
Choanoflagellate cell
Water
current
Food
particles
Water current
Sponge feeding cell
(choanocyte)
flagellum
microvilli (collar)
Figure 30.3 Choanoflagellates and Sponge Feeding Cells Are Almost Identical in Structure and Function.
Both are benthic
Both are sessile
Both feed using cells with nearly identical morphology
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11. ctenophores, sponges, cnidarians
Figure 30.5
Symmetry in animals evolved over time
(a) Radial symmetry
(b) Bilateral symmetry
Figure 30.5 Body Symmetry.
ctenophores, sponges, cnidarians
the rest of Animalia
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12. The defining feature of Kingdom Animalia is ?
Figure 30.8
(a) Nerve net:
diffuse neurons in hydra
(b) Central nervous system:
clustered neurons in earthworm
Cerebral
ganglion
(brain)
Ganglia
Cephalization eventually led to a central nerve system for sensing the enviornment and controlling movement and other responses.
Figure 30.8 Associations between Body Symmetry and the Nervous System.
The defining feature of Kingdom Animalia is ?
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13. The embryo of animals evolved three-embryonic layers
Figure 30.9
The embryo of animals evolved three-embryonic layers
And a body cavity (coelom) inside
Skin and nervous
system derived
from ectoderm
Muscles and
organs derived
from mesoderm
Coelom
(cavity lined
with mesoderm)
Mouth
Gut derived
from
endoderm
In protostomes, the mouth (stoma) develops first (proto-)
Figure 30.9 The Tube-within-a-Tube Body Plan Is Common in Animals.
Anus
In deuterostomes, the mouth (stoma) develops second (deutero-)
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