Endosymbiosis (proposed by Lynn Margulis)
is a relationship between two species in which one
organism lives inside the cell or cells of the other
organism (the host)
This is the root of the diversity of life.
http://evolution.berkeley.edu/evolibrary/article/_0_0/endosymbiosis_04
Mitochondria and plastids are derived from
prokaryotes that were engulfed by the ancestors of
early eukaryotic cells
Mitochondria evolved once by endosymbiosis of an
alpha proteobacterium
The ancestral host cell may have been an archaean
or a “protoeukaryote,” from a lineage related to, but
diverged from archaeal ancestors
What makes a Kingdom?
A Kingdom is a division of life,
right under Domain.
Boundless. “The Levels of Classification.” Boundless
Biology. Boundless, 03 Jul. 2014. Retrieved 12 Dec. 2014
from https://www.boundless.com/biology/textbooks/boundl
ess-biology-textbook/phylogenies-and-the-history-of-life-
20/organizing-life-on-earth-133/the-levels-of-classification-
541-11750//
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Welcome to Your Kingdom
The animal kingdom extends far beyond humans
and other animals we may encounter
1.3 million living species of animals have been
identified
Fig. 32-1
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• Animals are heterotrophs that ingest their
food
http://www.reefs.org/library/aquarium_net/0697/0697_1.html
http://greenanswers.com/q/183382/animals-wildlife/which-animal-
eats-most-food-every-day
Animal characteristics
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What makes an Animal?
• Animals are multicellular
eukaryotes
• Heterotrophs that digest internally
• Their cells lack cell walls
• Their bodies are held together by
structural proteins such as collagen
• Nervous tissue and muscle tissue
are unique to animals
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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 blastula
• The blastula undergoes gastrulation, forming
a gastrula with different layers of embryonic
tissues
The Earth is about 4.5 billion (4,500,000,000)
years old. The geological time scale divides up
this vast time interval.
The Earth is very old
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
living animals may have
lived between 675 and
875 million years ago
This ancestor may have
resembled modern
choanoflagellates,
protists that are the closest
living relatives of animals
The oldest fossils (bacteria) are between 3 billion and
3.5 billion years old.
More complex animals appeared in the oceans about
565 million years ago, and became much more common
about 542 million years ago. This is the start of a division
of geological time called the Phanerozoic Eon.
Phanerozoic means "visible life", and is the time in which
fossils are abundant. http://commonfossilsofoklahoma.snomnh.ou.edu/geological-time-scale
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Neoproterozoic Era (1 Billion–524 Million Years Ago)
Early members of the animal fossil record include
the Ediacaran biota, (pre-Cambrian) which dates
from 565 to 550 million years ago
• All life was soft-bodied
Mawsonites spriggi
Spriggina floundersi
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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
Several hypotheses
regarding the explosion
1. New predator-prey
relationships
2. A rise in atmospheric
oxygen
3. The evolution of the
Hox gene complex
http://geologycafe.com/class/chapter13.html
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
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Mesozoic Era (251–65.5 Million Years Ago)
• Coral reefs emerged, becoming important
marine ecological niches for other organisms
• During the Mesozoic era, dinosaurs were the
dominant terrestrial vertebrates
• The first mammals emerged
http://www.smithsonianmag.com/smart-news/dinosaurs-have-feathers-sure-
but-we-may-have-got-the-colors-all-wrong-10978826/?no-ist
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
Modern mammal orders and insects diversified during
the Cenozoic
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Animals can be characterized by “body plans”
A body plan is a set of morphological and
developmental traits – we will classify animals
by:
1. Symmetry
2. Tissues
3. Type of body Cavity
4. Fate of the blastopore
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• Hox regulates the development
of body form
• Lay out the basic body form of
all animals
• it doesn’t matter if it’s a mouse’s
head or a fly’s head that is
being built, the same gene
directs the process
• Jellyfish have only two Hox
genes, bilateria have at least
seven.
All animals, and only animals, have Hox (Homeobox)
genes
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• Many animals have at least one larval stage
• A larva is sexually immature and
morphologically distinct from the adult; it
eventually undergoes metamorphosis
Metamorphosis - Some animals change body
plans during their life-cycle
1. Symmetry
Animals can be categorized according to the
symmetry of their bodies, or lack of it
Sponges are asymmetrical – they have asymmetry
http://encina.pntic.mec.es/~nmeb0000/invertebrates/ranimal.html
http://biologismos.blogspot.com/2010_06_01_archive.html
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Animals can be categorized according to the
symmetry of their bodies, or lack of it
• Some animals have radial symmetry
(a) Radial symmetry Fig. 32-7
1. Symmetry
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(b) Bilateral symmetry
Fig. 32-7
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
1. Symmetry
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2. Tissues
• Tissues are collections of specialized cells
isolated from other tissues by membranous
layers
• During development 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.
• Diploblastic animals have ectoderm and
endoderm
• Triploblastic animals also have an intervening
mesoderm layer; these include all bilaterians
2. Tissues
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3. Body Cavities
• Most triploblastic animals possess a body
cavity
• A true body cavity is called a coelom and is
derived from mesoderm
3. Body Cavities
Animals that are Diploblastic (like jellyfish) or do
not form a blastula (like sponges) have no body
cavity. We say that they have No Coelom
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Triploblastic animals that lack a body cavity are
called acoelomates
(c) Acoelomate
Body covering
(from ectoderm)
Wall of digestive cavity (from endoderm)
Tissue- filled region
(from mesoderm)
3. Body Cavities
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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
Pseudocoelom
Body covering
(from ectoderm)
Muscle layer (from mesoderm)
Digestive tract
(from endoderm)
(b) Pseudocoelomate
3. Body Cavities
Fig. 32-8a
Coelom Body covering
(from ectoderm)
Digestive tract
(from endoderm)
Tissue layer lining coelom and suspending internal organs (from mesoderm)
(a) Coelomate
Coelomates are animals that possess a true coelom
3. Body Cavities
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4. Protostome and Deuterostome Development
• Based on early development, many animals
can be categorized as having protostome
development or deuterostome development
Zygote
Cleavage
Eight-cell stage
Cleavage Blastula
Cross section of blastula
Blastocoel
Gastrulation
Blastopore
Gastrula
Archenteron
Ectoderm
Endoderm
Blastocoel
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• The blastopore forms during gastrulation
• Protostome:blastopore becomes the mouth
• Deuterostome: the blastopore becomes the anus
Anus
Protostome development
(examples: molluscs,
annelids)
Deuterostome development
(examples: echinoderms,
chordates)
Anus
Mouth
Mouth
Digestive tube
(c) Fate of the blastopore
Key
Ectoderm
Mesoderm
Endoderm
Mouth develops from blastopore. Anus develops from blastopore. Fig. 32-9c
4. Protostome and Deuterostome Development
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• Protostome: the splitting of solid masses of
mesoderm forms the coelom
• Deuterostome: the mesoderm buds from the wall
of the archenteron to form the coelom
Coelom
Protostome development
(examples: molluscs,
annelids)
Deuterostome development
(examples: echinoderms,
chordates)
(b) Coelom formation
Key
Ectoderm
Mesoderm
Endoderm
Mesoderm Mesoderm
Coelom
Archenteron
Blastopore Blastopore
Solid masses of mesoderm
split and form coelom. Folds of archenteron
form coelom.
Fig. 32-9b
4. Protostome and Deuterostome Development
Figure 32.11
ANCESTRAL
PROTIST
Porifera
Ctenophora
Cnidaria
Acoela 770 million
years ago
680 million
years ago
670 million
years ago
Me
tazo
a
Eu
me
tazo
a
Bila
teria
Hemichordata
Echinodermata
Chordata
Platyhelminthes
Rotifera
Ectoprocta
Brachiopoda
Mollusca
Annelida
Nematoda
Arthropoda
De
ute
ros
tom
ia
Lo
ph
otro
ch
ozo
a
Ec
dys
ozo
a
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. True animals Eumetazoa is a clade of animals
with true tissues
4. Most animal phyla belong to the clade
Bilateria
5. Most animals (95%) are invertebrates,
animals that lack a backbone, only some
Chordata, are classified as vertebrates.
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You should now be able to:
1. List the characteristics define animals
2. Summarize key events of the Paleozoic, Mesozoic, and Cenozoic eras
3. Distinguish between the following pairs or sets of terms: radial and bilateral symmetry; grade and clade of animal taxa; diploblastic and triploblastic; spiral and radial cleavage; determinate and indeterminate cleavage; acoelomate, pseudocoelomate, and coelomate grades
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
4. Compare the developmental differences
between protostomes and deuterostomes
5. Compare the alternate relationships of
annelids and arthropods presented by two
different proposed phylogenetic trees
6. Distinguish between ecdysozoans and
lophotrochozoans