Transcript Chapter 7 Mammalian/Primate Evolutionary History

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
Chapter Outline
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Mammalian Evolution
The Emergence of Major Mammalian
Groups
Processes of Macroevolution
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.
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.
Approaches to Classification
Goal
Evolutionary
Systematics
Cladistics
Construction of a
phylogenetic tree
Construction of
a cladogram
Compare
specific traits
Construct classifications to show
Similarities
evolutionary relationships
Focus on homologies
Approaches to Classification
Evolutionary
Systematics
Differences
Might use any
homologous character
Attempts to make
ancestor-descendant
links
Attempts to place
fossils in a chronological
framework
Cladistics
Use only explicitly defined
derived characters
No attempt is made to make
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.
Speciation
 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 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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The positions of the
continents at the
beginning of the
Cenozoic (c. 65 m.y.a.).
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.
Lateral View of the Brain
Reptilian and Mammalian
teeth
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Mammals are
heterodont, they have
different kinds of
teeth; incisors,
canines, premolars,
and molars.
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.
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
Quick Quiz
1. 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.
2. 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.
3. The group of mammals that reproduce by
laying eggs and who generally have
more primitive traits than the other
mammals are the
a) monotremes.
b) metatherians.
c) marsupials.
d) placentals.
Answer: a
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The group of mammals that reproduce
by laying eggs and who generally have
more primitive traits than the other
mammals are the monotremes.
4. 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.