An Overview of Animal Diversity - Lake Central High School

LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 32
An Overview of Animal Diversity
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.

Figure 32.1
Overview: Welcome to Your Kingdom

Cell Structure and Specialization
• Animals are multicellular eukaryotes
• Their cells lack cell walls
• First off, animals are heterotrophs that ingest their
food (1)
• Their bodies are held together by structural
proteins such as collagen
• Nervous tissue and muscle tissue are unique,
defining characteristics of animals (2)
• Tissues are groups of cells that have a common
structure, function, or both
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Reproduction and Development
• Most animals reproduce sexually, with the diploid
stage usually dominating the life cycle (3)
• After a sperm fertilizes an egg, the zygote
undergoes rapid cell division called cleavage
• Cleavage leads to formation of a multicellular,
blastula- spherical layer of cells enclosing a
hollow, central cavity.
• The blastula undergoes gastrulation, forming a
gastrula.
Video: Sea Urchin Embryonic Development
© 2011 Pearson Education, Inc.

Figure 32.2-3
(4 &15)
Zygote
Cleavage
Blastocoel
Cleavage
Eight-cell
stage
Blastula
Cross section
of blastula
Gastrulation
Blastocoel
Endoderm
Ectoderm
Cross section
of gastrula
Archenteron
Blastopore

Zygote-The resulting single celled organism that follows the joining of sperm
and egg (fertilization)
Blastula- spherical layer of cells enclosing a hollow, central cavity.
Gastrula- early state of germ layer formation following the blastula stage,
consisting of the ectoderm and endoderm, enclosing a central cavity
Blastopore-The opening formed from the invagination of the blastula to form
a gastrula
Cleavage-Invagination formed from separated layers or tissue
Gastrulation-Process that converts a blastula to a gastrula.
Metamorphosis- a complete change of form, structure, or substance, as
transformation by magic or witchcraft. (5-6)

• 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 (7)
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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 developmental characteristics are
conservative
For example, the molecular control of gastrulation
is conserved among diverse animal groups
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Body Plan
• Animals can be categorized according to the
symmetry of their bodies, or lack of it
• Asymmetry are organisms that lack a central body
plan (Sponges). (11-12)
• Some animals have radial symmetry, with no
front and back, or left and right
• Two-sided symmetry is called bilateral symmetry
• Bilaterally symmetrical animals have
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– 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

Body Plan Examples
Asymetrical Radial Bilateral

Figure 32.7
(10 From
Knowledge)
(a) Radial symmetry
(b) Bilateral symmetry

• Radial animals are often sessile or planktonic
(drifting or weakly swimming)
• Sessile basically equals not moving
• Bilateral animals often move actively and have a
central nervous system (13-14 From thinking)
© 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
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• 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
– These include flatworms, arthropods, vertebrates,
and others (16)
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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
• Mesoderm is the middle germ layer and lines
• The ectoderm forms: the central nervous system, the lens of the eye, cranial
and sensory, the ganglia and nerves, pigment cells, head connective tissues,
the epidermis, hair, and mammary glands.
• The mesoderm forms: skeletal muscle, the skeleton, the dermis of skin,
connective tissue, the urogenital system, the heart, blood (lymph cells), the
kidney, and the spleen.
• The endoderm forms: the stomach, the colon, the liver, the pancreas, the
urinary bladder, the lining of the urethra, the epithelial parts of trachea, the
lungs, the pharynx, the thyroid, the parathyroid, and the intestines. (17)
© 2011 Pearson Education, Inc.

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
• A pseudocoelom is a body cavity derived from the
mesoderm and endoderm
• Triploblastic animals that possess a
pseudocoelom are called pseudocoelomates
• Triploblastic animals that lack a body cavity are
called acoelomates (18-20)
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Figure 32.8
(21)
(a) Coelomate
(b) Pseudocoelomate
Coelom
Digestive tract
(from endoderm)
Pseudocoelom
Digestive tract
(from endoderm)
Body covering
(from ectoderm)
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)
Body covering
(from ectoderm)
Muscle layer
(from
mesoderm)
(c) Acoelomate
Body covering
(from ectoderm)
Tissuefilled
region
(from
mesoderm)
Wall of digestive cavity
(from endoderm)

• Coelom………What does it do for us?
– Its fluid cushions suspended organs preventing injury
– Cavity enables internal organs to grow and move
independently of the outer body wall
– In soft body coelomates the coelom contains non
compressible fluid that acts like a skeleton muscle can
pull from
– (22)
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Protostome and Deuterostome Development
• Based on early development, many animals can
be categorized as having protostome
development or deuterostome development
• 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 (24-27)
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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
© 2011 Pearson Education, Inc.

Figure 32.9c
(23)
(c) Fate of the
blastopore
Protostome development
(examples: molluscs,
annelids)
Anus
Deuterostome development
(examples: echinoderms,
chordates)
Mouth
Key
Ectoderm
Mesoderm
Endoderm
Digestive tube
Mouth
Anus
Mouth develops from blastopore. Anus develops from blastopore.

Figure 32.9a
(28)
(a) Cleavage
Protostome development
(examples: molluscs,
annelids)
Deuterostome development
(examples: echinoderms,
chordates)
Eight-cell stage
Eight-cell stage
Key
Ectoderm
Mesoderm
Endoderm
Spiral and determinate
Radial and indeterminate

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 32.11
Porifera
ANCESTRAL
COLONIAL
FLAGELLATE
(29)
True tissues
Metazoa
Eumetazoa
Radial and
diploblastic
Triploblastic
Bilateria
Deuterostomia
Lophotrochozoa
Ecdysozoa
Ctenophora
Cnidaria
Acoela
Echinodermata
Chordata
Platyhelminthes
Rotifera
Ectoprocta
Brachiopoda
Mollusca
Annelida
Nematoda
Arthropoda
coelom
Acoelomate
coelom
Pseudocoelomate