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Chapter 5
Macroevolution: Processes of
Vertebrate and Mammalian
Evolution
Chapter Outline
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The Human Place in the Organic World
Principles of Classification
Definition of Species
Vertebrate Evolutionary History: A Brief
Summary
Mammalian Evolution
Chapter Outline
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The Emergence of Major Mammalian Groups
Processes of Macroevolution
Issue: Just When We Thought Things Couldn’t
Get Any Worse: Bushmeat and Ebola
Classification
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Classification is used to order organisms into
categories to show evolutionary relationships.
Example - human classification
Kingdom: Animalia
Subkingdom: Metazoan
Phyla: Chordata
Subphyla: Vertebrata
Class: Mammalia
Classification: Definitions
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Metazoa
Multicellular animals.
Chordata
The phylum of the animal kingdom that
includes vertebrates.
Vertebrates
Animals with segmented bony spinal
columns; includes fishes, amphibians,
reptiles, birds, and mammals.
Principles of Classification
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The field that specializes in establishing
the rules of classification is called
taxonomy.
Organisms are classified first on the basis
of physical similarities.
Basic physical similarities must reflect
evolutionary descent in order for them to
be useful.
Principles of Classification
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Homologies
Similarities based on descent from a
common ancestor.
Analogies
Similarities based on common function, with
no assumed common evolutionary descent.
Homoplasy
The separate evolutionary development of
similar characteristics in different groups of
organisms.
Homologies
Two Approaches to
Classification
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Evolutionary systematics
A traditional approach in which presumed
ancestors and descendants are traced in
time by analysis of homologous characters.
Cladistics
Attempts to make rigorous evolutionary
interpretations based solely on analysis of
certain types of homologous characters.
Question
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The scientific discipline that delineates
the rules of classification is
a) paleontology.
b) stratigraphy.
c) homology.
d) taxonomy.
Answer: d
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The scientific discipline that delineates the
rules of classification is taxonomy.
Ancestral and Modified
Characters
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Ancestral characters
Refers to characters inherited by a group of
organisms from a remote ancestor and thus
not diagnostic of groups (lineages) that
diverged after the character first appeared.
Derived characters
Refers to characters that are modified from
the ancestral condition and thus are
diagnostic of particular evolutionary lineages.
Evolutionary “Trees”: Development
of Passenger Vehicles
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The first divergence
is between cars and
trucks (I).
A later divergence
occurs between
luxury cars and
sports cars (II).
Evolutionary “Trees”: Development
of Passenger Vehicles
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SUVs diverge from
trucks, but like sports
cars, they have a
decorative racing stripe.
This is a homoplasy and
does not make SUVs
sports cars.
Classifications based on
a characteristic that can
appear independently in
different groups can lead
to an incorrect
conclusion.
Evolutionary Relationships of
Birds and Dinosaurs
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(a) Traditional view, showing no close
relationship. (b) Revised view, showing
common ancestry of birds and dinosaurs.
Cladogram
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Shows relationships of birds, dinosaurs, and other
terrestrial vertebrates. There’s no time scale, and both
living and fossil forms are shown along the same
dimension. Ancestor- descendant relationships aren’t
indicated.
Approaches to Classification
Goal
Similarities
Evolutionary
Systematics
Cladistics
Construction of a
phylogenetic tree
Construction of a
cladogram
•Compare specific traits
•Construct classifications to show
evolutionary relationships
•Focus on homologies
Approaches to Classification
Evolutionary
Systematics
Differences
Might use any homologous
character
Attempts to make ancestordescendant links
Attempts to place fossils in
a chronological framework
Cladistics
Use only defined derived
characters
No conclusions regarding
ancestor-descendant
relationships
All members of an evolutionary
group are interpreted in one
dimension
Definition of Species
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Biological species concept
Depiction of species as groups of
individuals capable of interbreeding, but
reproductively isolated from other such
groups.
Definition of Species
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Recognition species concept
 A depiction of species in which the key
aspect is the ability of individuals to identify
members of their own species for purposes
of mating.
This type of selective mating is a component
of a species concept emphasizing mating
and is therefore compatible with the
biological species concept.
Definition of Species
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Ecological species concept
The concept that a species is a group of
organisms exploiting a single niche.
This view emphasizes the role of natural
selection in separating species from one
another.
Definition of Species
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Phylogenetic species concept
Splitting many populations into
separate species based on an
identifiable parental pattern of ancestry.
Allopatric
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Living in different areas.
This pattern is important in the divergence
of closely related species from each other
and from their shared ancestral species
because it leads to reproductive isolation.
Speciation
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Process by which a new species evolves
from a prior species.
Speciation is the most basic process in
macroevolution.
Speciation Model
Recognition of Fossil Species
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The minimum biological category we would like
to define in fossil primate samples is the
species.
Variations
• Intraspecific - Variation is accounted for
by individual, age, and sex differences
seen within every biological species
• Interspecific - Variation represents
differences between reproductively
isolated groups.
Recognition of Fossil Species
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Defining where species boundaries begin
and end is often difficult.
“Splitters” are researchers who claim
speciation occurred frequently during
hominid evolution.
“Lumpers” assume speciation was less
common and see much variation as
being intraspecific.
Recognition of Fossil Genera
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A genus is a group of species composed of
members more closely related to each other
than to species from any other genus.
Species that are members of the same genus
share the same broad adaptive zone.
Members of the same genus should all share
derived characters not seen in members of
other genera.
Geological Time Scale
ERA
PERIOD
Tertiary
Began
m.y.a.
1.8
CENOZOIC
Quaternary
65
EPOCH
Holocene
Pleistocene
Pliocene
Miocene
Oligocene
Eocene
Paleocene
Began
m.y.a.
0.01
1.8
5
23
34
55
65
Geological Time Scale
ERA
PERIOD
(Began m.y.a.)
MESOZOIC
Cretaceous
136
Jurassic
190
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
225
280
345
395
430
500
570
PALEOZOIC
Geological Time Scale
Geological Eras
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Paleozoic
The first vertebrates appeared 500 m.m.y.a.
Mesozoic
Reptiles were dominant land vertebrates.
Placental mammals appeared 70 m.Y.A.
Cenozoic
Divided into two periods: Tertiary and
Quaternary and 7 epochs: Paleocene,
Eocene, Oligocene, Miocene, Pliocene,
Pleistocene and Holocene.
Continental Drift
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The movement of continents on sliding
plates of the earth’s surface.
As a result, the positions of large
landmasses have shifted drastically
during the earth’s history.
Continental drift
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The positions of the
continents during the
Mesozoic (c. 125
m.y.a.).
Pangea is breaking
up into a northern
landmass (Laurasia)
and a southern
landmass
(Gondwanaland).
Continental Drift
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(a) Positions of the continents during the Mesozoic.
Pangea is breaking up into a northern landmass
(Laurasia) and a southern landmass (Gondwanaland).
(b) Positions of the continents at the beginning of the
Cenozoic.
Ecological Niches
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The positions of species within their
physical and biological environments,
together making up the ecosystem.
A species’ ecological niche is defined by
such components as diet, terrain,
vegetation, type of predators,
relationships with other species, and
activity patterns, and each niche is unique
to a given species.
Epochs
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Categories of the geological time scale.
In the Cenozoic, epochs include
Paleocene
Eocene
Oligocene
Miocene
Pliocene
Pleistocene
Holocene
Mammalian Evolution
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The Cenozoic era is known as the Age of
Mammals.
After dinosaurs became extinct, mammals
underwent adaptive radiation, resulting in
rapid expansion and diversification.
The neocortex, which controls higher brain
functions, comprised the majority of brain
volume, resulting in greater ability to learn.
Reptilian and Mammalian
teeth
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Mammals are
heterodont, they have
different kinds of
teeth; incisors,
canines, premolars,
and molars.
Major Events in Early
Vertebrate Evolution
Question
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The divergence of reptiles into many
different forms describes
a) analogies.
b) sexual selection.
c) adaptive radiation.
d) homologies.
Answer: c
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The divergence of reptiles into many
different forms describes adaptive
radiation.
Time Unit Conversion Using
the Cosmic Calendar
1 yr = 15,000,000,000 yrs
1mth = 1,250,000,000 yrs
1 day = 41,000,000 yrs
1 hr = 1,740,000 yrs
1 min = 29,000 yrs
1 sec = 475 yrs
Big Bang
January 1
Formation of the earth
September 14
Origin of life on earth
September 25
Significant oxygen, atmosphere begins to December 1
develop
Time Unit Conversion Using
the Cosmic Calendar
1 yr = 15,000,000,000 yrs
1mth = 1,250,000,000 yrs
1 day = 41,000,000 yrs
1 hr = 1,740,000 yrs
1 min = 29,000 yrs
1 sec = 475 yrs
Precambrian ends; Paleozoic begins;
invertebrates flourish
December 17
Paleozoic ends and Mesozoic begins
December 25
Cretaceous period: first flowers;
dinosaurs become extinct
December 28
Mesozoic ends; Cenozoic begins;
adaptive radiation of placental mammals
December 29
Time Unit Conversion Using
the Cosmic Calendar
1 yr = 15,000,000,000 yrs
1mth = 1,250,000,000 yrs
1 day = 41,000,000 yrs
1 hr = 1,740,000 yrs
1 min = 29,000 yrs
1 sec = 475 yrs
December 31
Appearance of early hominoids
12:30 P.M.
First hominids
9:30 P.M.
Extensive cave painting in Europe
11:59 P.M.
Invention of agriculture
11:59:20 P.M.
Time Unit Conversion Using
the Cosmic Calendar
1 yr = 15,000,000,000 yrs
1mth = 1,250,000,000 yrs
1 day = 41,000,000 yrs
1 hr = 1,740,000 yrs
1 min = 29,000 yrs
1 sec = 475 yrs
December 31
Renaissance in Europe: Ming Dynasty in 11:59:59 P.M.
China; emergence of scientific method
Widespread development of science and NOW: the first
technology; emergence of a global
second of the New
culture; first steps in space exploration
Year
Heterodont
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Having different kinds of teeth;
characteristic of mammals, whose teeth
consist of incisors, canines, premolars,
and molars.
Endothermic
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Able to maintain internal body
temperature by producing energy through
metabolic processes within cells;
characteristic of mammals, birds, and
perhaps some dinosaurs.
Question
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An advantage of heterodont dentition is that it
a) allows the animal to defend itself more
efficiently.
b) allows for processing a wide variety of
foods.
c) opens up new ways of interacting with
potential mates.
d) allows the animal to grab prey that it
could not catch otherwise.
Answer: b
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An advantage of heterodont dentition is
that it allows for processing a wide
variety of foods.
Major Mammalian Groups
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Monotremes
Primitive, egg laying mammals
Marsupials
Infants complete development in an eternal
pouch
Placental
Longer gestation allows the central nervous
system to develop more completely
Adaptive Radiation
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A process that takes place when a life form
rapidly takes advantage of the many newly
available ecological niches.
A species, or group of species, will diverge into
as many variations as two factors allow:
1. Its adaptive potential.
2. The adaptive opportunities of the available
niches.
Gradualism versus
Punctuated Equilibrium
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The traditional view of evolution has
emphasized that change accumulates
gradually in evolving lineages, an idea
called phyletic gradualism.
Punctuated equilibrium is the concept
that evolutionary change proceeds
through long periods of stasis punctuated
by rapid periods of change.