Campbell Biology
Third Canadian Edition
Chapter 32
An Overview of Animal Diversity
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Key Concepts
• Animals are multicellular, heterotrophic eukaryotes with
tissues that develop from embryonic layers
• The history of animals spans more than half a billion years
• Animals can be characterized by “body plans”
• New views of animal phylogeny continue to be shaped by
new molecular data
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Overview: Welcome to Your Kingdom
• The animal kingdom extends far beyond humans and other
animals we commonly encounter
• Scientists have identified 1.3 million living species of
animals
Domain
king
dow
Dapofys
phylum
class
order
family
gens
species
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BioFlix: Coral Reef
Video: Coral Reef
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What do all these animals found in
Newfoundland have in common?
Figure 32.1 What do all these animals found in
Newfoundland have in common?
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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
• But several characteristics, taken together, sufficiently
define the group
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Nutritional Mode
• Animals are heterotrophs:
– They cannot construct all their own organic molecules
– They obtain organic molecules from their food, that
they ingest and digest within their bodies
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Cell Structure and Specialization
• Animals are multicellular eukaryotes
• They lack cell walls
• Their bodies are held together by structural proteins such
as collagen
• Nervous tissue and muscle tissues are unique, defining
characteristics of animals
• Tissues are groups of cells that act as a functional unit
sponyes
lack tive tissue
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An Overview of Animal Diversity (1 of 4)
THINK-PAIR-SHARE
simplest animal
on
earth
• Trichoplax adhaerens (Tp) is the only living species in the
phylum Placozoa. Tp feeds on marine microbes, mostly
unicellular green algae, by crawling atop the algae and
trapping it between its ventral surface and the substrate.
Enzymes are then secreted onto the algae, and the
resulting nutrients are absorbed. can shapeshift create holes
/
can
• In this respect, Tp is more similar to?
reproduce itself
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Reproduction and Development (1 of 2)
• Most animals reproduce sexually, with diploid stage usually
dominating 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
↳
Istthing
that
forms
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BioFlix: Sea Urchin Embryonic
Development
Video: Sea Urchin Embryonic Development
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Early embryonic development in
animals
Figure 32.2 Early embryonic
development in animals.
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Reproduction and Development (2 of 2)
• 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
regulating development of body form
• Although the Hox family of genes is highly conserved, it
can produce a wide diversity of animal morphology
ex:
the genes
decide where
body parts
messing with hox genes
results
rise
in
on
the
animal
.
abnormal body part place
;
arm
for
leg
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An Overview of Animal Diversity (2 of 4)
THINK-PAIR-SHARE
• What do plants and animals have in common?
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Concept 32.2: The history of animals
spans more than half a billion years
• The animal kingdom includes a great diversity of living
species and an even greater diversity of extinct ones
• The common ancestor of all living animals likely lived
between 700 and 770 million years ago
• Morphological and molecular data suggest that the
common ancestor may have resembled modern
choanoflagellates, protists that are closest living relatives
of animals
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Three lines of evidence that choanoflagellates
are closely related to animals
1. Cell morphology
2. Cell morphology unique to animal cells
3. DNA sequence homology
Figure 32.3 Three lines of evidence that choanoflagellates are closely
related to animals.
↑
-
video
he showed
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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 from 565 to 550 million years ago
Figure 32.4 Ediacaran fossils.
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Ediacaran era fossils
• Rangeomorph fossils found at Mistaken Point, Newfoundland are
some of the oldest fossils from the Ediacaran era, dating to
approximately 565 million years ago
Figure 32.5 Rangeomorph (Fractofusus) fossils.
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Paleozoic Era (542–251 Million Years
Ago) (1 of 2)
• 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
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Paleozoic Era (542–251 Million Years
Ago) (2 of 2)
• The Burgess Shale site in B.C. is rich in fossils from approximately 505
million years ago
Figure 32.6 A Cambrian seascape.
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Impact: The Burgess Shale and
Anomalocaris canadensis
• Burgess Shale is one of most significant fossil sites
• Shallow sea with animals from every major phylum (including soft
bodied)
Figure 32.7 Impact.
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Paleozoic Era
• There are several hypotheses regarding the cause of the
Cambrian explosion and decline of Ediacaran biota,
including:
– New predator-prey relationships
– A rise in atmospheric oxygen
– The evolution of Hox gene complex
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Paleozoic Era (542–251 Million Years
Ago)
• Animal diversity continued to increase through Paleozoic,
but was punctuated by mass extinctions
• Animals began to make an impact on land by 460 million
years ago
• Vertebrates made 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
• Ancestors of plesiosaurs were reptiles that returned to the
water
• The first mammals emerged
• During the Mesozoic era, dinosaurs were the dominant
terrestrial vertebrates
• 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 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 other have
changed multiple times over the course of evolution
– The molecular control of gastrulation has remained
unchanged for more than 500 million years
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Symmetry (1 of 3)
• Animals can be categorized according to symmetry of their bodies, or
lack of it
• Some have radial symmetry, with no front and back, or left and right
Figure 32.8 Body symmetry.
esided
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Symmetry (2 of 3)
• 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” concentrated at
the anterior end (development of a head), which is
called cephalization
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Symmetry (3 of 3)
• Radial animals are often sessile or planktonic (drifting or
weakly swimming)
• Bilateral animals often move actively and have a central
nervous system
CNS
Exceptions
:
some bird's beaks
flat fish
:
both
,
get
adaptations/evolve
eyes are
on
to
help their needs
top
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Tissues (1 of 3)
• 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 tissues
and organs of animal embryos
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Tissues (2 of 3)
↳outside
• Ectoderm is the germ layer covering the embryo’s surface
inside
->
• Endoderm is the innermost germ layer and lines the
developing digestive tube, called archenteron
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Tissues (3 of 3)
• Sponges and a few other groups lack true tissues
• Diploblastic animals have ectoderm and endoderm
– Includes cnidarians and a few other groups
less cmpix animals
• Triploblastic animals also have an intervening mesoderm
layer; these include all bilaterians
– Includes flatworms, arthropods, vertebrates, and others
more
cmpix
animals
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Body Cavities (1 of 2)
• Most triploblastic animals possess a body cavity
• A true body cavity is called a coelom and is derived from
mesoderm
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Body cavities of triploblastic animals (1 of 3)
• Coelomates are animals that possess a true coelom
Figure 32.9a Body cavities of triploblastic animals.
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Body cavities of triploblastic animals (2 of 3)
• A pseudocoelom is a body cavity derived from mesoderm and
endoderm
• Triploblastic animals possessing a pseudocoelom called
pseudocoelomates
Figure 32.9b Body cavities of triploblastic animals.
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Body cavities of triploblastic animals (3 of 3)
• Triploblastic animals that lack a body cavity are called acoelomates
Figure 32.9 Body cavities of triploblastic animals.
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Body Cavities (2 of 2)
• Coelomates and pseudocoelomates have similar body
plans 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 I
↳t
-
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Protostome and Deuterostome
↓Development
strong
-
first
• Based on early development, many animals can be
categorized as having protostome development or
deuterostome development
If
it
forms
mouth first its
if it Forms
anus
proto
first its dentro
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Cleavage (1 of 2)
• In protostome development, cleavage spiral and determinate
• In deuterostome development, cleavage radial and indeterminate
Figure 32.10a A comparison of protostome and deuterostome
development.
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Cleavage (2 of 2)
• 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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An Overview of Animal Diversity (3 of 4)
THINK-PAIR-SHARE
• At what stage does it become impossible to generate
identical twins?
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Coelom Formation
• In protostome development, splitting of solid masses of mesoderm
forms the coelom
• In deuterostome development, mesoderm buds from the wall of the
archenteron to form the coelom
Figure 32.10b A comparison of protostome and deuterostome
development.
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Fate of the Blastopore (1 of 2)
• 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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Fate of the Blastopore (2 of 2)
Figure 32.10c A comparison of protostome and
deuterostome development.
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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
• Zoologists recognize about three dozen animal phyla
• Phylogenies now combine morphological, molecular, and
fossil data
• Current debate in animal systematics led to development
of multiple hypotheses about relationships among animal
groups
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Animal Phylogeny
• There are 5 important points about the relationships
among living animals that 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, and
are called bilaterians
5. There are 3 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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A phylogeny of living animalsa
Figure 32.11 A phylogeny
of living animals.
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Progress in Resolving Bilaterian
Relationships
• The bilaterians are divided into three clades:
1. Deuterostomia
2. Ecdysozoa
3. 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 sportablthis
• Ecdysozoans are invertebrates that shed their
exoskeletons through a process called ecdysis
Figure 32.12 Ecdysis.
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Lophotrochozoans
going from
one group to other
Noname : learn
steps
or
• Some lophotrochozoans have a feeding structure called a
lophophore
• Others have distinct developmental stage called trochophore larva
Figure 32.13 Ecdysis.
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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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An Overview of Animal Diversity (4 of 4)
THINK-PAIR-SHARE
• What do humans and earthworms have in common?
True codom ?
*
insects & spiders
Arthropods
means
in
do not belong
joined
same
group
segments
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