Transcript Chapter 7 Mammalian/Primate Evolutionary History

CHAPTER 5
Processes of Macroevolution
Chapter Outline
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Discovering the Human Place in the Organic World
Principles of Classification
Constructing Classifications and Interpreting
Evolutionary Relationships
Definition of Species
Interpreting Species and Other Groups in the Fossil
Record
What Are Fossils and How Do They Form?
Chapter Outline
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Vertebrate Evolutionary History: A Brief History
Mammalian Evolution
The Emergence of Major Mammalian Groups
Processes of Macroevolution
Working Together: Microevolution and
Macroevolution
Focus Question
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Where do humans fit in the story of life on the
Earth?
The Human Place in the Organic World
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To deal scientifically with the tremendous diversity
of life on the planet, biologists develop a system of
classification.
Classification
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Organizes diversity into categories
Indicates evolutionary and genetic relationships
The kingdom Animalia includes 20 major phyla
(singular, phylum)
Chordata is one phyla and includes all animals with
a nerve cord, gill slits and supporting cord along
the back.
Vertebrates
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Animals with segmented, bony spinal columns;
includes fishes, amphibians, reptiles, birds, and
mammals.
Principles of Classification
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The field that establishes the rules of classification is
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 a common ancestor.
Analogies
 Similarities based on common function, with no
assumed common evolutionary descent.
Homoplasy
 Separate evolutionary development of similar
characteristics in different groups of organisms.
Homologies
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Similarities in the
forelimb bones of these
animals can be most
easily explained by
descent from a common
ancestor.
Homologies vs. Analogies
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How could an evolutionary biologist determine if a
trait is an analogy or a biology?
Constructing Classifications and Interpreting
Evolutionary Relationships
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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 (those considered to be derived characters).
Clade
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Lineage, or a group of organisms sharing a common
ancestor.
The group includes the common ancestor and all
descendants.
Ancestral and Derived (Modified) Characters
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Ancestral
 Characters inherited by a group of organisms from
a remote ancestor and not diagnostic of groups
that diverged after the character appeared; also
called primitive.
Derived (Modified) Characters that are modified
from the ancestral condition and thus are diagnostic
of particular evolutionary lineages.
An Example of Cladistic Analysis: Evolution of
Cars and Trucks
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From a common ancestor of
all passenger vehicles, the
first major divergence is
between cars and trucks (I).
A later divergence occurs
between luxury cars and
sports cars (II).
Derived features of each
grouping appear after its
divergence from other
groups.
An Example of Cladistic Analysis: Evolution of
Cars and Trucks
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In this “tree,” SUVs diverge
from trucks, but like sports
cars, have a decorative
racing stripe.
This is a homoplasy and
does not make SUVs sports
cars.
Classifications based on
one characteristic that can
appear in different groups
can lead to an incorrect
conclusion.
Using Cladistics to Interpret Real Organisms:
Birds and Dinosaurs
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Traditional view, no close relationship.
Using Cladistics to Interpret Real
Organisms: Birds and Dinosaurs
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Revised view, common ancestry of birds and dinosaurs.
Theropods
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Small- to medium-sized ground-living carnivorous
dinosaurs, dated to approximately 150 mya and
thought to be related to birds.
Shared Derived
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Relating to specific character traits shared in
common between two life-forms and considered the
most useful for making evolutionary interpretations.
The presence of feathers in the proposed
relationship between some (theropod) dinosaurs
and birds is an example
Phylogenetic Tree
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A chart showing evolutionary relationships as
determined by evolutionary systematics.
It contains a time component and implies ancestor
descendant relationships.
Cladogram
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A chart showing evolutionary relationships as
determined by cladistic analysis.
It’s based solely on interpretation of shared derived
characters.
It contains no time component and does not imply
ancestor-descendant relationships.
Cladogram
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This cladogram shows relationships of birds,
dinosaurs, and other terrestrial vertebrates.
There’s no time scale and ancestor-descendant
relationships aren’t indicated.
Cladograms vs. Phylogenetic Trees
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How are these two approaches combined by
physical anthropologists?
Definition of Species
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The biological species concept emphasizes
interbreeding and 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
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A and B have not yet
diverged.
Speciation Model
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A and B are just
beginning to diverge.
Genetic differences
accumulate (mutation,
genetic drift)
If different habitats,
different selective
pressures
Speciation Model
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A and B have diverged
to a point where they’re
no longer able to
reproduce; speciation is
complete.
Speciation and the Processes of
Evolution
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Why is an understanding of the various processes of
evolution important to understanding speciation?
Interpreting Species and Other Groups in the
Fossil Record
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The goal is to make meaningful biological statements
about the variation represented in groups of
organisms.
Identifying individual variation, age changes,
variation due to sex (sexual dimorphism)
Fossil species are understood based on observations
of living animals
Intraspecific variation
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Variation accounted for by individual, age, and sex
differences seen within every biological species
Interspecific variation
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Variation representing differences between
reproductively isolated groups
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.
Fossils
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Traces of ancient organisms and formed in several ways
Mineralization occurs very slowly as water carrying minerals,
such as silica or iron, seeps into the tiny spaces within a bone.
In some cases, the original minerals within the bone or tooth
can be completely replaced.
Traces of life forms that include insects trapped in tree sap,
leaf imprints, footprints, skeletal remains and remains of
digestive tracts
Taphonomy is the study of how bones and other materials
come to be buried in the earth and preserved as fossils
Geological Time Scale
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The organization of earth history into eras, periods,
and epochs; commonly used by geologists and
paleoanthropologists.
Geological Time Scale
Geological Eras
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Paleozoic
 Vertebrates
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appeared 500 mya.
Mesozoic
 Reptiles
were dominant land vertebrate, placental
mammals appeared 70 mya.
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Cenozoic
 Divided
epochs.
into Tertiary and Quaternary periods and 7
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 mya.).
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 mya).
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, the Age of Mammals.
The enlargement of the cerebrum, especially the
neocortex, which controls higher brain functions, resulting
in more nerve cells
A longer, more intense period of growth in utero
Distinctive dentition, termed a heterodont dentition, with
3 incisors, 1 canine, 4 premolars, and 3 molars in each
quarter of mouth
Maintenance of constant internal body temperature,
warm-bloodedness, and endothermic
Early Vertebrate Evolution
Lateral View of the Brain
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Lateral view of the brain in fishes, reptiles, and
primates.
Note the increased size of the cerebral cortex
of the primate brain.
Reptilian and Mammalian Teeth
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Reptilian teeth (top) are
homodont.
Mammals are
heterodont, they have
different kinds of teeth;
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.
Emergence of the Major
Mammalian Groups
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Monotremes
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Placental
Processes of Macroevolution
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Operate on the whole species, rather than on
individuals or populations
Take a longer period of time to have a noticeable
impact
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.
Generalized and Specialized
Characteristics
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Refer to the adaptive potential of a particular trait
Generalized if a trait is adapted for many functions: a
mammalian limb with five fairly flexible digits,
adapted for many possible functions
Specialized if a trait is limited to a narrow set of
functions: hand or foot suited for specialized function
of stable weight support in an upright posture
Why It Matters
Question
 Why is it useful to know about the age of the earth
and continental drift? What does this have to do
with “us” and our world today? What does it really
matter if the earth is only a few thousand years old,
as some people claim?
Why It Matters
We have reason to be concerned about the power of
nature and one approach is to study geological beds
that are millions of years old. From this record we can
compute the periodicity of major earthquakes and
volcanic eruptions.
QUICK QUIZ
1. The scientific discipline that delineates the rules of
classification is
a)
b)
c)
d)
paleontology.
stratigraphy.
homology.
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)
b)
c)
d)
allows the animal to defend itself more efficiently.
allows for processing a wide variety of foods.
opens up new ways of interacting with potential
mates.
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.
The uneven, nongradual evolutionary process of
long stasis and quick spurts has been termed
_________________.
3.
a)
b)
punctuated equilibrium
gradualism
Answer: a
a)
Punctuated equilibrium refers to the uneven,
nongradual process of long stasis and quick spurts.
4. The divergence of reptiles into many different
forms describes
a)
b)
c)
d)
analogies.
sexual selection.
adaptive radiation.
homologies.
Answer: c
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The divergence of reptiles into many different
forms describes adaptive radiation.
5. Given the huge amount of organic diversity
displayed in the record, as well as the vast amount of
time involved, two major organizing perspectives
prove indispensible. The perspectives are:
a)
schemes of formal classification
b)
geological time scale
c)
timeframe for next major earthquake
d)
a and b
e)
None of the above
Answer: d
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Perspectives gained from schemes of formal
classification and geological timescale prove
indispensible for organizing understanding of
organic diversity in the record.