Download Chapter 32 - An Overview of Animal Diversity

Figure 32.1
CAMPBELL
BIOLOGY
Figure 32.1a
A Kingdom of Consumers
TENTH
EDITION
Reece • Urry • Cain • Wasserman • Minorsky • Jackson
!  Most animals are mobile and use traits such as
strength, speed, toxins, or camouflage to detect,
capture, and eat other organisms
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!  For example, the chameleon captures insect prey
with its long, sticky, quick-moving tongue
An Overview of
Animal Diversity
Lecture Presentation by
Nicole Tunbridge and
Kathleen Fitzpatrick
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Concept 32.1: Animals are multicellular,
heterotrophic eukaryotes with tissues that
develop from embryonic layers
Nutritional Mode
Cell Structure and Specialization
Reproduction and Development
!  Animals are heterotrophs that ingest their food
!  Animals are multicellular eukaryotes
!  There are exceptions to nearly every criterion for
distinguishing animals from other life-forms
!  Their cells lack cell walls
!  Several characteristics, taken together, sufficiently
define the group
!  Their bodies are held together by structural
proteins such as collagen
!  Most animals reproduce sexually, with the diploid
stage usually dominating the life cycle
!  After a sperm fertilizes an egg, the zygote
undergoes rapid cell division called cleavage
!  Cleavage leads to formation of a multicellular,
hollow blastula
!  Nervous tissue and muscle tissue are unique,
defining characteristics of animals
!  The blastula undergoes gastrulation, forming a
gastrula with different layers of embryonic tissues
!  Tissues are groups of similar cells that act as a
functional unit
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Figure 32.2-1
Figure 32.2-2
Zygote
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Figure 32.2-3
Zygote
Cleavage
Zygote
Cleavage
Eight-cell
stage
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Eight-cell
stage
Eight-cell
stage
Cleavage
Blastula
Video: Sea Urchin Embryonic Development
(Time Lapse)
Cleavage
Blastocoel
Cleavage
Cross section
of blastula
Blastula
Blastocoel
Cross section
of blastula
Gastrulation
Cross section
of gastrula
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Blastopore
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Blastocoel
Endoderm
Ectoderm
Archenteron
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Concept 32.2: The history of animals spans
more than half a billion years
!  Most animals have at least one larval stage
!  A larva is sexually immature and morphologically
distinct from the adult; it eventually undergoes
metamorphosis to become a juvenile
!  A juvenile resembles an adult, but is not yet
sexually mature
!  Most animals, and only animals, have Hox genes
that regulate the development of body form
!  More than 1.3 million animal species have been
named to date; far more are estimated to exist
!  Although the Hox family of genes has been highly
conserved, it can produce a wide diversity of
animal morphology
!  The common ancestor of all living animals likely
lived between 700 and 770 million years ago
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Steps in the Origin of Multicellular Animals
!  Morphological and molecular evidence points to a
group of protists called choanoflagellates as the
closest living relatives to animals
!  The common ancestor may have resembled
modern choanoflagellates
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Figure 32.3
Figure 32.4
Neoproterozoic Era (1 Billion–542 Million Years
Ago)
!  The origin of multicellularity requires the evolution
of new ways for cells to adhere (attach) and signal
(communicate) to each other
Individual
choanoflagellate
Choanoflagellates
OTHER
EUKARYOTES
!  Molecular analysis has revealed similarities
between genes coding for proteins involved in
adherence and attachment in choanoflagellates
and animals
Sponges
Animals
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“CCD” domain (only
found in animals)
Fruit
fly
Mouse
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Figure 32.5
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Figure 32.5a
1.5 cm
!  Early animal embryos and evidence of predation
have also been found in Neoproterozoic rocks
Hydra
Collar cell
(choanocyte)
Other
animals
!  Early members of the animal fossil record include
the Ediacaran biota, which dates back to about
560 million years ago
Choanoflagellate
Figure 32.5b
1.5 cm
0.4 cm
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Figure 32.6
0.4 cm
Bore hole
0.1 mm
(a) Mawsonites spriggi
(b) Spriggina floundersi
(a) Mawsonites spriggi
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(b) Spriggina floundersi
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Figure 32.7
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Figure 32.7a
Figure 32.7b
Paleozoic Era (542–251 Million Years Ago)
!  The Cambrian explosion (535 to 525 million
years ago) marks the earliest fossil appearance of
many major groups of living animals
!  Most of the fossils from the Cambrian explosion
are of bilaterians, organisms that have the
following traits:
1 cm
Hallucigenia fossil (530 mya)
!  Bilaterally symmetric form
1 cm
!  Complete digestive tract
Hallucigenia
fossil (530 mya)
!  One-way digestive system
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!  There are several hypotheses regarding the cause
of the Cambrian explosion and decline of
Ediacaran biota
!  New predator-prey relationships
!  Animal diversity continued to increase through the
Paleozoic, but was punctuated by mass
extinctions
!  Animals began to make an impact on land by 450
million years ago
!  A rise in atmospheric oxygen
!  Vertebrates made the transition to land around
365 million years ago
!  The evolution of the Hox gene complex
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Mesozoic Era (251–65.5 Million Years Ago)
Cenozoic Era (65.5 Million Years Ago to the
Present)
!  Coral reefs emerged, becoming important marine
ecological niches for other organisms
!  The beginning of the Cenozoic era followed mass
extinctions of both terrestrial and marine animals
!  The ancestors of plesiosaurs were reptiles that
returned to the water
!  These extinctions included the large, nonflying
dinosaurs and the marine reptiles
!  During the Mesozoic era, dinosaurs were the
dominant terrestrial vertebrates
!  Mammals increased in size and exploited vacated
ecological niches
!  The first mammals emerged
!  The global climate cooled
!  Flowering plants and insects diversified
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Figure 32.8
Concept 32.3: Animals can be characterized by
“body plans”
!  Zoologists sometimes categorize animals
according to a body plan, a set of morphological
and developmental traits
Symmetry
!  Animals can be categorized according to the
symmetry of their bodies, or lack of it
!  Two-sided symmetry is called bilateral symmetry
!  Bilaterally symmetrical animals have
!  Some animals have radial symmetry, with no
front and back, or left and right
!  Some body plans have been conserved, while
others have changed multiple times over the
course of evolution
!  A dorsal (top) side and a ventral (bottom) side
(a) Radial symmetry
!  A right and left side
!  Anterior (front) and posterior (back) ends
!  Many also have sensory equipment, such as a
brain, concentrated in their anterior end
(b) Bilateral symmetry
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Tissues
!  Radial animals are often sessile or planktonic
(drifting or weakly swimming)
!  Animal body plans also vary according to the
organization of the animal’s tissues
!  Ectoderm is the germ layer covering the embryo’s
surface
!  Bilateral animals often move actively and have a
central nervous system
!  Tissues are collections of specialized cells isolated
from other tissues by membranous layers
!  Endoderm is the innermost germ layer and lines
the developing digestive tube, called the
archenteron
!  During development, three germ layers give rise to
the tissues and organs of the animal embryo
!  Sponges and a few other groups lack true tissues
!  Diploblastic animals have ectoderm and
endoderm
!  These include cnidarians and a few other groups
!  Triploblastic animals also have an intervening
mesoderm layer; these include all bilaterians
!  These include flatworms, arthropods, vertebrates,
and others
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Figure 32.9
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Figure 32.9a
Figure 32.9b
Body Cavities
(b) Psuedocoelomate
(a) Coelomate
!  Most triploblastic animals possess a body cavity
Coelom
!  A true body cavity is called a coelom and is
derived from mesoderm
Digestive tract
(from endoderm)
!  Coelomates are animals that possess a true
coelom
Body covering
(from ectoderm)
Body covering
(from ectoderm)
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)
Pseudocoelom
(a) Coelomate
(b) Pseudocoelomate
Coelom
Muscle layer
(from
mesoderm)
Digestive tract
(from endoderm)
(c) Acoelomate
Key
Ectoderm
Body covering
(from ectoderm)
Wall of digestive cavity
(from endoderm)
Tissuefilled region
(from
mesoderm)
Pseudocoelom
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)
Ectoderm
Mesoderm
Digestive tract
(from endoderm)
Ectoderm
Endoderm
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Muscle layer
(from
mesoderm)
Key
Key
Endoderm
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Digestive tract
(from endoderm)
Mesoderm
Body covering
(from ectoderm)
Body covering
(from ectoderm)
Mesoderm
Endoderm
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Figure 32.9c
!  A pseudocoelom is a body cavity derived from the
mesoderm and endoderm
(c) Acoelomate
Body covering
(from ectoderm)
Tissuefilled region
(from
mesoderm)
!  Terms such as coelomates and
pseudocoelomates refer to organisms that have a
similar body plan and belong to the same grade
!  Triploblastic animals that possess a
pseudocoelom are called pseudocoelomates
!  A grade is a group whose members share key
biological features
!  A grade is not necessarily a clade, an ancestor
and all of its descendants
Wall of digestive cavity
(from endoderm)
Key
Ectoderm
Mesoderm
Endoderm
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!  Triploblastic animals that lack a body cavity are
called acoelomates
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Figure 32.10
Protostome and Deuterostome Development
Figure 32.10a
Cleavage
(a) Cleavage
!  Based on early development, many animals can
be categorized as having protostome
development or deuterostome development
Protostome development
(examples: molluscs,
annelids)
Eight-cell stage
Deuterostome development
(examples: echinoderms,
chordates)
Eight-cell stage
!  In protostome development, cleavage is spiral
and determinate
Radial and indeterminate
Spiral and determinate
!  In deuterostome development, cleavage is radial
and indeterminate
!  Indeterminate cleavage makes possible identical
twins, and embryonic stem cells
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Protostome development
(examples: molluscs,
annelids)
Eight-cell stage
Deuterostome development
(examples: echinoderms,
chordates)
Eight-cell stage
Spiral and determinate
Radial and indeterminate
Coelom
Mesoderm
Blastopore
Blastopore
Solid masses of mesoderm
split and form coelom.
(c) Fate of the
blastopore
Mesoderm
Folds of archenteron
form coelom.
Mouth
Anus
Digestive tube
Key
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Figure 32.10b
(a) Cleavage
Archenteron
!  With indeterminate cleavage, each cell in the early
stages of cleavage retains the capacity to develop
into a complete embryo
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Coelom
(b) Coelom
formation
Ectoderm
Mesoderm
Endoderm
Mouth
Mouth develops from blastopore.
Anus
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Anus develops from blastopore.
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Coelom Formation
Fate of the Blastopore
Figure 32.10c
Protostome development
(examples: molluscs,
annelids)
(b) Coelom
formation
Deuterostome development
(examples: echinoderms,
chordates)
Coelom
(c) Fate of the
blastopore
Protostome development
(examples: molluscs,
annelids)
Anus
Archenteron
Digestive tube
Coelom
Key
Mesoderm
Ectoderm
Mesoderm
Endoderm
Blastopore
Solid masses of mesoderm
split and form coelom.
Deuterostome development
(examples: echinoderms,
chordates)
Mouth
Blastopore
Mesoderm
Folds of archenteron
form coelom.
!  In protostome development, the splitting of solid
masses of mesoderm forms the coelom
!  In deuterostome development, the mesoderm
buds from the wall of the archenteron to form the
coelom
Key
Ectoderm
Mesoderm
Endoderm
Mouth
Mouth develops
from blastopore.
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Concept 32.4: Views of animal phylogeny
continue to be shaped by new molecular and
morphological data
The Diversification of Animals
!  In protostome development, the blastopore
becomes the mouth
!  In deuterostome development, the blastopore
becomes the anus
Anus
Anus develops
from blastopore.
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!  The blastopore forms during gastrulation and
connects the archenteron to the exterior of the
gastrula
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Figure 32.11
Porifera
Hemichordata
Echinodermata
Chordata
Platyhelminthes
Lophotrochozoa
Rotifera
Ectoprocta
Brachiopoda
Mollusca
Annelida
Ecdysozoa
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Deuterostomia
Figure 32.11a
Bilateria
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Acoela
670 million
years ago
5. There are three major clades of bilaterian animals, all of
which are invertebrates, animals that lack a backbone,
except Chordata, which are classified as vertebrates
because they have a backbone
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Eumetazoa
2. Sponges are basal animals
4. Most animal phyla belong to the clade Bilateria
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Cnidaria
680 million
years ago
3. Eumetazoa (“true animals”) is a clade of animals with
true tissues
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Ctenophora
770 million
years ago
1. All animals share a common ancestor
!  Phylogenies now combine morphological,
molecular, and fossil data
Metazoa
!  Five important points about the relationships among living
animals are reflected in their phylogeny
!  Zoologists recognize about three dozen animal
phyla
!  By 500 million years ago, most animal phyla with
members alive today were established
ANCESTRAL
PROTIST
Nematoda
Arthropoda
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Figure 32.11b
Deuterostomia
Porifera
Metazoa
Ctenophora
Cnidaria
Acoela
Bilateria
680 million
years ago
!  Ecdysozoa is a clade of invertebrates that shed
their exoskeletons through a process called
ecdysis
!  Deuterostomia includes hemichordates (acorn
worms), echinoderms (sea stars and relatives),
and chordates
Rotifera
Ectoprocta
Brachiopoda
!  This clade includes both vertebrates and
invertebrates
Mollusca
Annelida
Ecdysozoa
670 million
years ago
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!  The bilaterians are divided into three clades:
Deuterostomia, Ecdysozoa, and Lophotrochozoa
Chordata
Platyhelminthes
Lophotrochozoa
770 million
years ago
Eumetazoa
ANCESTRAL
PROTIST
Hemichordata
Echinodermata
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Nematoda
Arthropoda
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Figure 32.12
Figure 32.12a
Future Directions in Animal Systematics
!  Lophotrochozoa is another clade of bilaterian
invertebrates
Lophophore
!  Systematics, like all fields of scientific research, is
an ongoing, dynamic process of inquiry
Lophophore
Apical tuft
of cilia
!  Some lophotrochozoans have a feeding structure
called a lophophore
!  Three outstanding questions are the focus of
current research
!  Others go through a distinct developmental stage
called the trochophore larva
1. Are sponges monophyletic?
Mouth
2. Are ctenophores basal metazoans?
Anus
(a) Lophophore feeding
structures of an ectoproct
(b) Structure of a trochophore
larva
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Figure 32.UN01
3. Are acoelomate flatworms basal bilaterians?
(a) Lophophore feeding
structures of an ectoproct
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Figure 32.UN02
Figure 32.UN03
Figure 32.UN04
1
2
3
4
5
6
7
8
9
10
11
5.8
35
2.5
26
38.6
33
59.1
25
50.8
58
147.5
25
30
34
38
45
68
73
77
83
94
172.5
560 mya:
Ediacaran animals
Era
Neoproterozoic
1,000
Σ
Σ
Sx
535−525 mya:
Cambrian explosion
Σ
542
365 mya:
Early land
animals
Origin and
diversification
of dinosaurs
Paleozoic
251
Millions of years ago (mya)
Ctenophora
Diversification
of mammals
Mesozoic
Cenozoic
65.5
Cnidaria
True
tissues
Acoela (basal
bilaterians)
Deuterostomia
0
Bilateral
symmetry
Sy
Three germ
layers
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Figure 32.UN05
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Lophotrochozoa
Ecdysozoa
Bilateria (most animals)
i
Eumetazoa
Animal Phylum
Porifera
Platyhelminthes
Cnidaria
Nematoda
Echinodermata
Cephalochordata
Arthropoda
Urochordata
Mollusca
Annelida
Vertebrata
No. of Cell
Types (yi)
Metazoa
Porifera
(basal animals)
No. of
miRNAs (xi)
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Blastopore Fate
Phyla
Protostomy (P)
Platyhelminthes, Rotifera, Nematoda; most
Mollusca, most Annelida; few Arthropoda
Deuterostomy (D)
Echinodermata, Chordata; most Arthropoda;
few Mollusca, few Annelida
Neither (N)
Acoela
Source: A. Hejnol and M. Martindale, The mouth, the anus, and the
blastopore open questions about questionable openings. In Animal Evolution: Genomes, Fossils and Trees, eds. D. T. J. Littlewood and M. J. Telford,
Oxford University Press, pp. 33–40 (2009).
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