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CAMPBELL
BIOLOGY Reece • Urry • Cain • Wasserman • Minorsky • Jackson
© 2014 Pearson Education, Inc.
TENTH EDITION
32 An Overview of Animal Diversity
Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick
© 2014 Pearson Education, Inc.
A Kingdom of Consumers
! Most animals are mobile and use traits such as strength, speed, toxins, or camouflage to detect, capture, and eat other organisms
! For example, the chameleon captures insect prey with its long, sticky, quick-moving tongue
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Figure 32.1
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Figure 32.1a
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Concept 32.1: Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers ! There are exceptions to nearly every criterion for
distinguishing animals from other life-forms
! Several characteristics, taken together, sufficiently define the group
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Nutritional Mode
! Animals are heterotrophs that ingest their food
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Cell Structure and Specialization
! Animals are multicellular eukaryotes
! Their cells lack cell walls
! Their bodies are held together by structural proteins such as collagen
! Nervous tissue and muscle tissue are unique, defining characteristics of animals
! Tissues are groups of similar cells that act as a functional unit
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Reproduction and Development
! 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
! The blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues
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Figure 32.2-1 Zygote
Cleavage Eight-cell
stage
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Figure 32.2-2 Zygote
Cleavage Eight-cell
stage
Cleavage Blastocoel
Cross section of blastula
Blastula
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Figure 32.2-3 Zygote
Cleavage Eight-cell
stage
Cleavage Blastocoel
Cross section of blastula
Blastula
Gastrulation
Blastocoel Endoderm Ectoderm Archenteron
Cross section of gastrula
Blastopore 11
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Video: Sea Urchin Embryonic Development (Time Lapse)
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! 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
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! Most animals, and only animals, have Hox genes that regulate the development of body form
! Although the Hox family of genes has been highly conserved, it can produce a wide diversity of animal morphology
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Concept 32.2: The history of animals spans more than half a billion years ! More than 1.3 million animal species have been
named to date; far more are estimated to exist
! 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
Individual choanoflagellate
Choano- flagellates
OTHER EUKARYOTES Sponges
Other animals
Collar cell (choanocyte)
Anim
als
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! The origin of multicellularity requires the evolution of new ways for cells to adhere (attach) and signal (communicate) to each other
! Molecular analysis has revealed similarities between genes coding for proteins involved in adherence and attachment in choanoflagellates and animals
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Figure 32.4
Choano- flagellate
Hydra
Fruit fly
Mouse
“CCD” domain (only found in animals)
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Neoproterozoic Era (1 Billion–542 Million Years Ago) ! Early members of the animal fossil record include
the Ediacaran biota, which dates back to about 560 million years ago
! Early animal embryos and evidence of predation have also been found in Neoproterozoic rocks
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Figure 32.5
1.5 cm
(a) Mawsonites spriggi
0.4 cm
(b) Spriggina floundersi
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Figure 32.5a
1.5 cm
(a) Mawsonites spriggi
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Figure 32.5b
0.4 cm
(b) Spriggina floundersi
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Figure 32.6
Bore hole
0.1 mm
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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:
! Bilaterally symmetric form
! Complete digestive tract
! One-way digestive system 25
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Figure 32.7
Hallucigenia fossil (530 mya)
1 cm
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Figure 32.7a
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Figure 32.7b
Hallucigenia fossil (530 mya) 1 cm
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! There are several hypotheses regarding the cause of the Cambrian explosion and decline of Ediacaran biota
! New predator-prey relationships
! A rise in atmospheric oxygen
! The evolution of the Hox gene complex
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! 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
! Vertebrates made the transition to land around 365 million years ago
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Mesozoic Era (251–65.5 Million Years Ago)
! Coral reefs emerged, becoming important marine ecological niches for other organisms
! The ancestors of plesiosaurs were reptiles that returned to the water
! During the Mesozoic era, dinosaurs were the dominant terrestrial vertebrates
! The first mammals emerged
! Flowering plants and insects diversified
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Cenozoic Era (65.5 Million Years Ago to the Present) ! The beginning of the Cenozoic era followed mass
extinctions of both terrestrial and marine animals
! These extinctions included the large, nonflying dinosaurs and the marine reptiles
! Mammals increased in size and exploited vacated ecological niches
! The global climate cooled
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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
! Some body plans have been conserved, while others have changed multiple times over the course of evolution
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Symmetry
! Animals can be categorized according to the symmetry of their bodies, or lack of it
! Some animals have radial symmetry, with no front and back, or left and right
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Figure 32.8
(a) Radial symmetry
Bilateral symmetry (b) 35
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! Two-sided symmetry is called bilateral symmetry
! Bilaterally symmetrical animals have
! A dorsal (top) side and a ventral (bottom) side
! 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
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! Radial animals are often sessile or planktonic (drifting or weakly swimming)
! Bilateral animals often move actively and have a central nervous system
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Tissues
! Animal body plans also vary according to the organization of the animal’s tissues
! Tissues are collections of specialized cells isolated from other tissues by membranous layers
! During development, three germ layers give rise to the tissues and organs of the animal embryo
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! Ectoderm is the germ layer covering the embryo’s surface
! Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron
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! 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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Body Cavities
! Most triploblastic animals possess a body cavity
! A true body cavity is called a coelom and is derived from mesoderm
! Coelomates are animals that possess a true coelom
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Figure 32.9
(a) Coelomate
Key Ectoderm
Mesoderm
Endoderm
Coelom Body covering (from ectoderm)
Tissue layer lining coelom and suspending internal organs (from mesoderm) Digestive tract
(from endoderm)
Body covering (from ectoderm)
Muscle layer (from mesoderm)
Pseudo- coelom
Digestive tract (from endoderm)
(c) Acoelomate Body covering (from ectoderm)
Tissue- filled region (from mesoderm)
Wall of digestive cavity (from endoderm)
(b) Psuedocoelomate
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Figure 32.9a
(a) Coelomate
Key Ectoderm Mesoderm Endoderm
Coelom Body covering (from ectoderm)
Tissue layer lining coelom and suspending internal organs (from mesoderm)
Digestive tract (from endoderm)
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Figure 32.9b
(b) Pseudocoelomate
Key Ectoderm Mesoderm Endoderm
Body covering (from ectoderm)
Muscle layer (from mesoderm)
Pseudo- coelom
Digestive tract (from endoderm)
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Figure 32.9c
(c) Acoelomate
Body covering (from ectoderm) Tissue-
filled region (from mesoderm)
Wall of digestive cavity (from endoderm)
Key Ectoderm Mesoderm Endoderm
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! A pseudocoelom is a body cavity derived from the mesoderm and endoderm
! Triploblastic animals that possess a pseudocoelom are called pseudocoelomates
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! Triploblastic animals that lack a body cavity are called acoelomates
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! Terms such as coelomates and pseudocoelomates refer to organisms that have a similar body plan and belong to the same grade
! 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
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Protostome and Deuterostome Development
! Based on early development, many animals can be categorized as having protostome development or deuterostome development
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Cleavage
! In protostome development, cleavage is spiral and determinate
! In deuterostome development, cleavage is radial and indeterminate
! With indeterminate cleavage, each cell in the early stages of cleavage retains the capacity to develop into a complete embryo
! Indeterminate cleavage makes possible identical twins, and embryonic stem cells
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Figure 32.10 Protostome development
(examples: molluscs, annelids)
Deuterostome development (examples: echinoderms,
chordates) (a) Cleavage
Key Ectoderm Mesoderm Endoderm
(b) Coelom formation
(c) Fate of the blastopore
Eight-cell stage Eight-cell stage
Spiral and determinate Radial and indeterminate
Coelom
Archenteron
Coelom Mesoderm Blastopore
Solid masses of mesoderm split and form coelom.
Folds of archenteron form coelom.
Blastopore Mesoderm
Anus
Digestive tube
Mouth Anus
Mouth
Mouth develops from blastopore. Anus develops from blastopore. 51
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Figure 32.10a
Protostome development (examples: molluscs,
annelids)
Deuterostome development (examples: echinoderms,
chordates) (a) Cleavage Eight-cell stage
Spiral and determinate
Eight-cell stage
Radial and indeterminate
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Figure 32.10b
Protostome development (examples: molluscs,
annelids)
Deuterostome development (examples: echinoderms,
chordates) (b) Coelom
formation
Key Ectoderm Mesoderm Endoderm
Coelom
Archenteron
Coelom Blastopore Mesoderm Blastopore Mesoderm
Solid masses of mesoderm split and form coelom.
Folds of archenteron form coelom.
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Figure 32.10c
Protostome development (examples: molluscs,
annelids)
Deuterostome development (examples: echinoderms,
chordates) (c) Fate of the
blastopore
Key Ectoderm Mesoderm Endoderm
Anus
Mouth Mouth develops from blastopore.
Digestive tube
Anus
Mouth
Anus develops from blastopore.
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Coelom Formation
! 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
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Fate of the Blastopore
! The blastopore forms during gastrulation and connects the archenteron to the exterior of the gastrula
! In protostome development, the blastopore becomes the mouth
! In deuterostome development, the blastopore becomes the anus
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Concept 32.4: Views of animal phylogeny continue to be shaped by new molecular and morphological data ! By 500 million years ago, most animal phyla with
members alive today were established
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The Diversification of Animals
! Zoologists recognize about three dozen animal phyla
! Phylogenies now combine morphological, molecular, and fossil data
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! Five important points about the relationships among living animals are reflected in their phylogeny
1. All animals share a common ancestor
2. Sponges are basal animals
3. Eumetazoa (“true animals”) is a clade of animals with true tissues
4. Most animal phyla belong to the clade Bilateria
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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Figure 32.11
ANCESTRAL PROTIST
Porifera
Ctenophora
Cnidaria
Acoela 770 million years ago
680 million years ago
670 million years ago
Metazoa
Eumetazoa
Bilateria
Hemichordata
Echinodermata
Chordata
Platyhelminthes
Rotifera
Ectoprocta
Brachiopoda
Mollusca
Annelida
Nematoda
Arthropoda
Deuterostom
ia
Lophotrochozoa Ecdysozoa
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Figure 32.11a
Porifera
Ctenophora
Cnidaria
Acoela
ANCESTRAL PROTIST
770 million years ago
680 million years ago
670 million years ago
Metazoa
Eumetazoa
Bilateria
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Figure 32.11b
Hemichordata
Echinodermata
Chordata
Platyhelminthes
Rotifera
Ectoprocta
Brachiopoda
Mollusca
Annelida
Nematoda
Arthropoda
Deuterostom
ia
Lophotrochozoa Ecdysozoa 62
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! The bilaterians are divided into three clades: Deuterostomia, Ecdysozoa, and Lophotrochozoa
! Deuterostomia includes hemichordates (acorn worms), echinoderms (sea stars and relatives), and chordates
! This clade includes both vertebrates and invertebrates
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! Ecdysozoa is a clade of invertebrates that shed their exoskeletons through a process called ecdysis
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! Lophotrochozoa is another clade of bilaterian invertebrates
! Some lophotrochozoans have a feeding structure called a lophophore
! Others go through a distinct developmental stage called the trochophore larva
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Figure 32.12
Lophophore feeding structures of an ectoproct
(a)
Lophophore
Structure of a trochophore larva
(b)
Anus
Mouth
Apical tuft of cilia
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Figure 32.12a
Lophophore feeding structures of an ectoproct
(a)
Lophophore
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Future Directions in Animal Systematics
! Systematics, like all fields of scientific research, is an ongoing, dynamic process of inquiry
! Three outstanding questions are the focus of current research
1. Are sponges monophyletic?
2. Are ctenophores basal metazoans?
3. Are acoelomate flatworms basal bilaterians?
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Figure 32.UN01
Animal Phylum Porifera
Platyhelminthes Cnidaria
Nematoda Echinodermata
Cephalochordata Arthropoda Urochordata
Mollusca Annelida
Vertebrata
i
1 2 3 4 5
7 6
8 9
10 11
5.8 35 2.5
26 38.6 33 59.1 25 50.8 58
147.5
No. of miRNAs (xi)
Sy �
Σ �
No. of Cell Types (yi)
25 30 34 38 45 68 73 77 83 94
172.5
Sx �
Σ � Σ �
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Figure 32.UN02
535−525 mya: Cambrian explosion
560 mya: Ediacaran animals
365 mya: Early land
animals
Origin and diversification
of dinosaurs Diversification
of mammals Era
Neoproterozoic Paleozoic Mesozoic Ceno- zoic
1,000 542 251 65.5 0 Millions of years ago (mya)
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Figure 32.UN03
Porifera (basal animals)
Ctenophora
Cnidaria
Acoela (basal bilaterians)
Deuterostomia
Lophotrochozoa
Ecdysozoa
True tissues
Bilateral symmetry
Three germ layers
Metazoa Eum
etazoa
Bilateria (m
ost animals)
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Figure 32.UN04
Blastopore Fate Phyla
Protostomy (P)
Deuterostomy (D)
Neither (N)
Source: A. Hejnol and M. Martindale, The mouth, the anus, and the blastopore�open questions about questionable openings. In Animal Evolu- tion: Genomes, Fossils and Trees, eds. D. T. J. Littlewood and M. J. Telford, Oxford University Press, pp. 33–40 (2009).
Platyhelminthes, Rotifera, Nematoda; most Mollusca, most Annelida; few Arthropoda Echinodermata, Chordata; most Arthropoda; few Mollusca, few Annelida Acoela
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Figure 32.UN05
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