Chapter 5
Macroevolution: Processes of
Vertebrate and Mammalian
Evolution
Chapter Outline
I.
II.
III.
IV.
V.
VI.
VII.
The Human Place in the Organic World
Principles of Classification
Definition of Species
Vertebrate Evolutionary History: A Brief
Summary
Mammalian Evolution
The Emergence of Major Mammalian
Groups
Processes of Macroevolution
I. The Human Place in the
Organic World


Classification to order organisms into categories
 to show evolutionary relationships.
Example - human classification
 Kingdom: Animalia
 Subkingdom: Metazoan
 Phyla: Chordata
 Subphyla: Vertebrata
 Class: Mammalia
I. Classification: Definitions



Metazoa
 Multicellular animals.
Chordata
 The phylum of the animal kingdom that
includes vertebrates.
Vertebrates
 Animals w segmented bony spinal columns;
(includes fishes, amphibians, reptiles, birds, and mammals).
II. Principles of Classification



Taxonomy- rules of classification.
Classified first on physical similarities.
Basic physical similarities must reflect
evolutionary descent in order for them to
be useful.
II.Principles of Classification



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.
II. Two Approaches to
Classification


Evolutionary Systematics (Phylogenic Tree)
 Presumed ancestors and descendants are
traced in time, by analysis of homologous
characters.
Cladistics (Cladogram)
 Attempts to make rigorous evolutionary
interpretations based solely on analysis of
certain types of homologous characters.
II. Ancestral and Modified
Characters


Ancestral characters
 Refers to characters inherited by a group of
organisms from a remote ancestor. (not
lineages).
Derived characters
 Refers to characters that are modified from
the ancestral condition. (Diagnostic of
particular evolutionary lineages)
II. 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
II. 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
III. Definition of Species


Biological species concept
 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.
III. Recognition of Fossil
Species

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.
III. Recognition of Fossil
Species

Defining where species boundaries begin
and end is often difficult.
 “Splitters” claim speciation occurred
frequently during hominid evolution.
 “Lumpers” assume speciation was less
common, & variation as being
intraspecific.
IV.Geological Time Scale
ERA
PERIOD
Quaternary
Began
m.y.a.
1.8
CENOZOIC
Tertiary
65
EPOCH
Holocene
Pleistocene
Pliocene
Miocene
Oligocene
Eocene
Paleocene
Began
m.y.a.
0.01
1.8
5
23
34
55
65
IV.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
IV.Geological Eras



Paleozoic
 The first vertebrates appeared 500 m.y.a.
(Cambrian period)
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.
VI. What caused such an
explosion?



Prior to 1 bya, all life on Earth
reproduced asexually – by making
clones of themselves
1 bya: organisms began reproducing
sexually.
We now have organisms exchanging
genetic information allowing for mutation,
genetic variation, and phenotypic
variation all of which allow for
evolutionary change to take speed
V.Mammalian Evolution



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.
Ecological Niches


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
-Type of Predators
 Terrain
- Activity patterns
 Vegetation
-Relationships w/other species
 Type of predators
 Each niche is unique to a given species.
Adaptive Radiation


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.
VI. Emergence of Major
Mammalian Groups



Monotremes
 Primitive, egg laying mammals
Marsupials
 Infants complete development in an external
pouch
Placental
 Longer gestation allows the central nervous
system to develop more completely
VII. Modes of Evolutionary
Change
Darwinian Gradualism:
 The view, held by Darwin, that evolution
is slow and steady with cumulative
change.
 Often exemplified as a branching tree
VII. Modes of Evolutionary
Change- Macroevolution
Punctuated Equilibrium:
 The view that species tend to remain stable
 evolutionary changes occur fairly suddenly
 Adaptive equilibrium of a species is
punctuated (interrupted) by the evolution of a
new species from the parent population
 Often exemplified, in contrast to Darwinian
gradualism, as a bush rather than a neatly
branched tree
 Dead ends, and frequent off-shoots are
common
VII. Punctuated Equilibrium



Put forth by Stephen Jay Gould
Accounts for the lack of intermediary
fossils – if change occurred quickly, it is
more likely that the intermediate stages
did not fossilize as frequently
Evolutionary change does not come from
gradual change within a species
(microevolution) but from new species
branching from existing ones
(macroevolution)
Quick Quiz
1. The scientific discipline that delineates
the rules of classification is
a) paleontology.
b) stratigraphy.
c) homology.
d) taxonomy.
Answer: d

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

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

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

The divergence of reptiles into many
different forms describes adaptive
radiation.