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16/04/12 Overview: Welcome to Your Kingdom
An Overview of Animal Diversity & Introduc>on to Development •  The animal kingdom extends far beyond humans
and other animals we may encounter
•  Scientists have identified 1.3 million living species
of animals
Chapter 32 Animation: Coral Reef
© 2011 Pearson Education, Inc.
Figure 32.1
Concept 32.1: Animal 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
© 2011 Pearson Education, Inc.
1 16/04/12 Nutritional Mode
•  Animals are heterotrophs that ingest their food
© 2011 Pearson Education, Inc.
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 cells that have a common
structure, function, or both
© 2011 Pearson Education, Inc.
Figure 32.2-3
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
Zygote Cleavage Blastocoel Cleavage Eight-­‐cell stage Blastula Cross sec5on of blastula Gastrula5on Blastocoel Endoderm Ectoderm Archenteron Video: Sea Urchin Embryonic Development
Cross sec5on of gastrula Blastopore © 2011 Pearson Education, Inc.
2 16/04/12 •  Many animals have at least one larval stage
•  A larva is sexually immature and morphologically
distinct from the adult; it eventually undergoes
metamorphosis
•  A juvenile resembles an adult, but is not yet
sexually mature
© 2011 Pearson Education, Inc.
•  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
© 2011 Pearson Education, Inc.
Figure 32.3
Concept 32.2: The history of animals
spans more than half a billion years
Choanoflagellates OTHER EUKARYOTES Sponges Animals •  The animal kingdom includes a great diversity of
living species and an even greater diversity of
extinct ones
•  The common ancestor of living animals may have
lived between 675 and 800 million years ago
•  This ancestor may have resembled modern
choanoflagellates, protists that are the closest
living relatives of animals
Individual choanoflagellate Other animals Collar cell (choanocyte) © 2011 Pearson Education, Inc.
3 16/04/12 Figure 32.4a
Neoproterozoic Era (1 Billion–542
Million Years Ago)
1.5 cm •  Early members of the animal fossil record include
the Ediacaran biota, which dates from 565 to 550
million years ago
(a) Mawsonites spriggi © 2011 Pearson Education, Inc.
Figure 32.4b
0.4 cm 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
•  There are several hypotheses regarding the cause
of the Cambrian explosion and decline of
Ediacaran biota
(b) Spriggina floundersi –  New predator-prey relationships
–  A rise in atmospheric oxygen
–  The evolution of the Hox gene complex
© 2011 Pearson Education, Inc.
4 16/04/12 Figure 32.5
•  Animal diversity continued to increase through the
Paleozoic, but was punctuated by mass
extinctions
•  Animals began to make an impact on land by 460
million years ago
•  Vertebrates made the transition to land around 360
million years ago
© 2011 Pearson Education, Inc.
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
© 2011 Pearson Education, Inc.
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
© 2011 Pearson Education, Inc.
5 16/04/12 Concept 32.3: Animals can be
characterized by body plans
RESULTS 1 Early stages of development •  Zoologists sometimes categorize animals
according to a body plan, a set of morphological
and developmental traits
•  Some developmental characteristics are
conservative
100 µm Figure 32.6
2 32-­‐cell stage Site of gastrula5on 3 Early gastrula stage -  For example, the molecular control of gastrulation
is conserved among diverse animal groups
Site of gastrula5on 4 Embryos with blocked β-­‐catenin ac5vity © 2011 Pearson Education, Inc.
Figure 32.6b
100 µm Figure 32.6a
Early stage of development Site of gastrula5on 32-­‐cell stage 6 16/04/12 Figure 32.6c
Figure 32.6d
Site of gastrula5on Embryos with blocked β-­‐catenin ac5vity Early gastrula stage Figure 32.7
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
(a) Radial symmetry (b) Bilateral symmetry © 2011 Pearson Education, Inc.
7 16/04/12 •  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 (head) and posterior (tail) ends
–  Cephalization, the development of a head
© 2011 Pearson Education, Inc.
•  Radial animals are often sessile or planktonic
(drifting or weakly swimming)
•  Bilateral animals often move actively and have a
central nervous system
© 2011 Pearson Education, Inc.
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
© 2011 Pearson Education, Inc.
•  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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8 16/04/12 Body Cavities
•  Sponges and a few other groups lack true tissues
•  Diploblastic animals have ectoderm and
endoderm
–  These include cnidarians and comb jellies
•  Triploblastic animals also have an intervening
mesoderm layer; these include all bilaterians
•  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
–  These include flatworms, arthropods, vertebrates,
and others
© 2011 Pearson Education, Inc.
Figure 32.8
© 2011 Pearson Education, Inc.
Figure 32.8a
(a) Coelomate Coelom Diges5ve tract (from endoderm) Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) (a) Coelomate Coelom (b) Pseudocoelomate Body covering (from ectoderm) Pseudocoelom Diges5ve tract (from endoderm) Muscle layer (from mesoderm) Diges5ve tract (from endoderm) (c) Acoelomate Body covering (from ectoderm) Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Tissue-­‐ filled region (from mesoderm) Wall of diges5ve cavity (from endoderm) 9 16/04/12 Figure 32.8b
•  A pseudocoelom is a body cavity derived from the
mesoderm and endoderm
•  Triploblastic animals that possess a pseudocoelom
are called pseudocoelomates
(b) Pseudocoelomate Body covering (from ectoderm) Pseudocoelom Diges5ve tract (from endoderm) Muscle layer (from mesoderm) © 2011 Pearson Education, Inc.
Figure 32.8c
•  Triploblastic animals that lack a body cavity are
called acoelomates
(c) Acoelomate Body covering (from ectoderm) Tissue-­‐ filled region (from mesoderm) Wall of diges5ve cavity (from endoderm) © 2011 Pearson Education, Inc.
10 16/04/12 Protostome and Deuterostome
Development
•  Coelomates and pseudocoelomates 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 descendents
© 2011 Pearson Education, Inc.
•  Based on early development, many animals can
be categorized as having protostome
development or deuterostome development
© 2011 Pearson Education, Inc.
Figure 32.9
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
Protostome development (examples: molluscs, annelids) (a) Cleavage Deuterostome development (examples: echinoderms, chordates) Eight-­‐cell stage Eight-­‐cell stage Spiral and determinate Radial and indeterminate (b) Coelom forma5on Coelom Archenteron Coelom Mesoderm Blastopore Blastopore Solid masses of mesoderm split and form coelom. (c) Fate of the blastopore Mesoderm Folds of archenteron form coelom. Anus Mouth Diges5ve tube Key Ectoderm Mesoderm Endoderm Mouth Mouth develops from blastopore. Anus Anus develops from blastopore. © 2011 Pearson Education, Inc.
11 16/04/12 Figure 32.9a
Coelom Formation
(a) Cleavage Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) Eight-­‐cell stage Eight-­‐cell stage •  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 Spiral and determinate Radial and indeterminate © 2011 Pearson Education, Inc.
Figure 32.9b
Fate of the Blastopore
(b) Coelom forma5on Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) Coelom Archenteron Coelom Key Ectoderm Mesoderm Endoderm Mesoderm Blastopore Solid masses of mesoderm split and form coelom. Blastopore Mesoderm •  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
Folds of archenteron form coelom. © 2011 Pearson Education, Inc.
12 16/04/12 Figure 32.9c
(c) Fate of the blastopore Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) Anus Mouth Diges5ve tube Key Ectoderm Mesoderm Endoderm Mouth Mouth develops from blastopore. Anus Anus develops from blastopore. Concept 32.4: New views of animal
phylogeny are emerging from
molecular data
•  Zoologists recognize about three dozen animal
phyla
•  Phylogenies now combine morphological,
molecular, and fossil data
•  Current debate in animal systematics has led to
the development of multiple hypotheses about the
relationships among animal groups
© 2011 Pearson Education, Inc.
Figure 32.10
Porifera Cnidaria Eumetazoa Metazoa Ctenophora Protostomia Bilateria Deuterostomia •  One hypothesis of animal phylogeny is based
mainly on morphological and developmental
comparisons
ANCESTRAL COLONIAL FLAGELLATE Ectoprocta Brachiopoda Echinodermata Chordata Platyhelminthes Ro5fera Mollusca Annelida Arthropoda Nematoda © 2011 Pearson Education, Inc.
13 16/04/12 Figure 32.11
Porifera Ctenophora Eumetazoa Metazoa Cnidaria Acoela Bilateria Echinodermata Chordata Platyhelminthes Lophotrochozoa Deuterostomia •  One hypothesis of animal phylogeny is based
mainly on molecular data
ANCESTRAL COLONIAL FLAGELLATE Ro5fera Ectoprocta Brachiopoda Mollusca Ecdysozoa Annelida Nematoda Arthropoda © 2011 Pearson Education, Inc.
Points of Agreement
1.  All animals share a common ancestor
2.  Sponges are basal animals
3.  Eumetazoa is a clade of animals
(eumetazoans) with true tissues
4.  Most animal phyla belong to the clade Bilateria,
and are called bilaterians
5.  Chordates and some other phyla belong to the
clade Deuterostomia
© 2011 Pearson Education, Inc.
Progress in Resolving Bilaterian
Relationships
•  The morphology-based tree divides bilaterians into
two clades: deuterostomes and protostomes
•  In contrast, recent molecular studies indicate three
bilaterian clades: Deuterostomia, Ecdysozoa, and
Lophotrochozoa
•  Ecdysozoans shed their exoskeletons through a
process called ecdysis
© 2011 Pearson Education, Inc.
14 16/04/12 Figure 32.12
•  Some lophotrochozoans have a feeding
structure called a lophophore
•  Others go through a distinct developmental stage
called the trochophore larva
© 2011 Pearson Education, Inc.
Figure 32.13
Figure 32.13a
Lophophore Apical tu_ of cilia Lophophore Mouth Anus (a) Lophophore feeding structures of an ectoproct (b) Structure of a trochophore larva (a) Lophophore feeding structures of an ectoproct 15 16/04/12 Figure 32.UN01
Future Directions in Animal
Systematics
•  Phylogenetic studies based on larger databases
will likely provide further insights into animal
evolutionary history
© 2011 Pearson Education, Inc.
Figure 32.UN02
Figure 32.UN03
Common ancestor of all animals Metazoa Porifera (basal animals) 565 mya: Ediacaran biota 365 mya: Early land animals Origin and diversifica5on of dinosaurs Ctenophora Diversifica5on of mammals Paleozoic Neoproterozoic 1,000 542 251 Millions of years ago (mya) Mesozoic Ceno-­‐ zoic 65.5 Cnidaria True 5ssues Acoela (basal bilaterians) 0 Deuterostomia Bilateral symmetry Three germ layers Lophotrochozoa Bilateria (most animals) Era Eumetazoa 535–525 mya: Cambrian explosion Ecdysozoa 16 16/04/12 Figure 32.UN04
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Dumb
King
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Domain
Kingdom
Phylum (Phyla)*
Class
Order
Family
Genus (Genera)
Species
(Sub-species)
*In Botany, Phyla are called Divisions 17