Chapter 31: Animal Origins and Lophotrochozoans
CHAPTER 31
Animal Origins and
Lophotrochozoans

Chapter 31: Animal Origins and Lophotrochozoans
Chapter 31: Animal Origins and Lophotrochozoans
Descendants of a Common Ancestor
The Animal Way of Life
Clues to Evolutionary Relationships among
Animals
Body Plans Are Basic Structural Designs
Sponges: Loosely Organized Animals

Chapter 31: Animal Origins and Lophotrochozoans
Chapter 31: Animal Origins and Lophotrochozoans
Cnidarians: Cell Layers and Blind Guts
Ctenophores: Complete Guts and Tentacles
The Evolution of Bilaterally Symmetrical
Animals
Protostomes and Deuterostomes: An Early
Lineage Split

Chapter 31: Animal Origins and Lophotrochozoans
Chapter 31: Animal Origins and Lophotrochozoans
Simple Lophotrochozoans
Lophophorates: An Ancient Body Plan
Spiralians: Wormlike Body Plans
Segmented Bodies: Improved Locomotion

Chapter 31: Animal Origins and Lophotrochozoans
Descendants of a Common
Ancestor
• All members of the kingdom Animalia are believed to have a common flagellated protist ancestor.
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Chapter 31: Animal Origins and Lophotrochozoans
Descendants of a Common
Ancestor
• The specialization of cells made possible the complex, multicellular body plan of animals.
6

Chapter 31: Animal Origins and Lophotrochozoans
The Animal Way of Life
• Animals obtain their food—complex organic molecules—by active expenditure of energy.
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Chapter 31: Animal Origins and Lophotrochozoans
Clues to Evolutionary
Relationships among Animals
• Morphological, developmental, and molecular data support similar animal phylogenies.
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Chapter 31: Animal Origins and Lophotrochozoans
Clues to Evolutionary
Relationships among Animals
• An animal’s body cavity is correlated with its ability to move.
• Based on this, animals are classified as acoelomates, pseudocoelomates, or coelomates.
Review Figure
31.1
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Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.1
figure 31-01.jpg
Figure 31.1

Chapter 31: Animal Origins and Lophotrochozoans
Clues to Evolutionary
Relationships among Animals
• The two major animal lineages— protostomes and deuterostomes—are believed to have separated early in animal evolution.
Review Figure
31.2
11

Chapter 31: Animal Origins and Lophotrochozoans
Figure 31.2
figure 31-02.jpg
Figure 31.2

Chapter 31: Animal Origins and Lophotrochozoans
Body Plans Are Basic
Structural Designs
• Most animals have radial or bilateral symmetry.
• Radially symmetrical animals move slowly, if at all.
• Those with bilateral symmetry have more rapid movements and sensory organs.
Review Figure
31.3
13

Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.3
figure 31-03.jpg
Figure 31.3

Chapter 31: Animal Origins and Lophotrochozoans
Sponges: Loosely Organized
Animals
• Sponges are simple animals that lack cell layers and body symmetry, but have several cell types.
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Chapter 31: Animal Origins and Lophotrochozoans
Sponges: Loosely Organized
Animals
• Sponges feed via choanocytes, feeding cells that filter out small organisms and nutrients.
Review Figure
31.4
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Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.4
figure 31-04.jpg
Figure 31.4

Chapter 31: Animal Origins and Lophotrochozoans
Cnidarians: Cell Layers and
Blind Guts
• Cnidarians are radially symmetrical and have two cell layers.
• With nematocyst-studded tentacles, they capture prey larger and more complex than themselves.
Review Figure
31.7
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Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.7
figure 31-07.jpg
Figure 31.7

Chapter 31: Animal Origins and Lophotrochozoans
Cnidarians: Cell Layers and
Blind Guts
• Most cnidarian life cycles have a sessile polyp and a free-swimming, sexual medusa stage, but some species lack one of the stages.
Review Figures
31.8
, 31.9
,
31.10
20

Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.8
figure 31-08.jpg
Figure 31.8

Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.9
Figure 31.9
figure 31-09.jpg

Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.10
figure 31-10.jpg
Figure 31.10

Chapter 31: Animal Origins and Lophotrochozoans
Ctenophores: Complete Guts and Tentacles
• Ctenophores, descendants of the first split in the lineage of bilaterally symmetrical animals, are marine carnivores with simple life cycles.
Review Figure
31.12
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Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.12
Figure 31.12
figure 31-12.jpg

Chapter 31: Animal Origins and Lophotrochozoans
The Evolution of Bilaterally
Symmetrical Animals
• Common ancestors of bilateral animals, urbilaterians, were probably simple, bilaterally symmetrical animals composed of flattened masses of cells.
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Chapter 31: Animal Origins and Lophotrochozoans
Protostomes and Deuterostomes: An Early Lineage Split
• Protostomes and deuterostomes have been evolving separately since the Cambrian period.
• Protostomes have a ventral nervous system, paired nerve cords, and larvae with compound cilia.
• Deuterostomes have a dorsal nervous system and larvae with single cilia.
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Chapter 31: Animal Origins and Lophotrochozoans
Protostomes and Deuterostomes: An Early Lineage Split
• Protostomes split into two major classes— lophotrochozoans and ecdysozoans.
Review Figure
31.14
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Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.14
Figure 31.14
figure 31-14.jpg

Chapter 31: Animal Origins and Lophotrochozoans
Simple Lophotrochozoans
• Flatworms have no body cavity, lack organs for oxygen transport, have one gut entrance, and move via cilia.
• Many species are parasitic.
Review Figures
31.15
, 31.16
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Chapter 31: Animal Origins and Lophotrochozoans
Figure 31.15
figure 31-15.jpg
Figure 31.15

Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.16
figure 31-16.jpg
Figure 31.16

Chapter 31: Animal Origins and Lophotrochozoans
Simple Lophotrochozoans
• No larger than many ciliated protists, rotifers have highly developed internal organs.
Review Figure
31.17
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Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.17
figure 31-17.jpg
Figure 31.17

Chapter 31: Animal Origins and Lophotrochozoans
Lophophorates: An Ancient
Body Plan
• The lophotrochozoan lineage split into two branches, the lophophorates and the spiralians.
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Chapter 31: Animal Origins and Lophotrochozoans
Lophophorates: An Ancient
Body Plan
• The lophophore dominates the anatomy of many lophophorate animals.
Review Figure
31.18
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Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.18
Figure 31.18
figure 31-18.jpg

Chapter 31: Animal Origins and Lophotrochozoans
Lophophorates: An Ancient
Body Plan
• Bryozoans are colonial lophophorates that can move their lophophores.
Review Figure
31.20
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Chapter 31: Animal Origins and Lophotrochozoans figure 31-20.jpg
Figure
31.20
Figure 31.20

Chapter 31: Animal Origins and Lophotrochozoans
Lophophorates: An Ancient
Body Plan
• Brachiopods were much more abundant in the past than they are today.
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Chapter 31: Animal Origins and Lophotrochozoans
Spiralians: Wormlike Body
Plans
• The spiralian lineage gave rise to many phyla, most of whose members have wormlike body forms.
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Chapter 31: Animal Origins and Lophotrochozoans
Spiralians: Wormlike Body
Plans
• Ribbon worms have a complete digestive tract and capture prey with a reversible proboscis.
Review Figure
31.22
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Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.22
Figure 31.22
figure 31-22.jpg

Chapter 31: Animal Origins and Lophotrochozoans
Segmented Bodies: Improved
Locomotion
• Annelids are a diverse group of segmented worms that live in marine, freshwater, and terrestrial environments.
Review Figure
31.23
44

Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.23
Figure 31.23
figure 31-23.jpg

Chapter 31: Animal Origins and Lophotrochozoans
Segmented Bodies: Improved
Locomotion
• Mollusks evolved from segmented ancestors.
• The three basic components of the molluscan body plan are the foot, mantle, and visceral mass.
Review Figure
31.25
46

Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.25
– Part
1
Figure 31.25 – Part 1 figure 31-25a.jpg

Chapter 31: Animal Origins and Lophotrochozoans
Figure
31.25 –
Part 2 figure 31-25b.jpg
Figure 31.25 – Part 2

Chapter 31: Animal Origins and Lophotrochozoans
Segmented Bodies: Improved
Locomotion
• The molluscan body plan yields a diverse array of animals that superficially appear very different from one another.
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