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LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 25
The History of Life on Earth
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
• macroevolutionary
– terrestrial vertebrates
– mass extinctions
– origin of flight in birds
• Chemical and physical processes on early Earth
may have produced very simple cells through a
sequence of stages:
1. Abiotic synthesis of small organic molecules
2. Joining of these small molecules into
macromolecules
3. Packaging of molecules into protocells
4. Origin of self-replicating molecules
© 2011 Pearson Education, Inc.
Figure 25.1
Synthesis of Organic Compounds on Early
Earth
• Earth formed about 4.6 billion years ago, along
with the rest of the solar system
• Bombardment of Earth by rocks and ice likely
vaporized water and prevented seas from forming
before 4.2 to 3.9 billion years ago
• Earth’s early atmosphere likely contained water
vapor and chemicals released by volcanic
eruptions (nitrogen, nitrogen oxides, carbon
dioxide, methane, ammonia, hydrogen, hydrogen
sulfide)
© 2011 Pearson Education, Inc.
• Oparin and Haldane: 1920s: early atmosphere
was a reducing environment
• Miller and Urey: 1953, experiments for abiotic
synthesis of organic molecules in a reducing
atmosphere is possible
– the first organic compounds may have been
synthesized near volcanoes or deep-sea vents
– Amino acids have also been found in meteorites
© 2011 Pearson Education, Inc.
Abiotic Synthesis of Macromolecules
• RNA monomers: spontaneously form from simple
molecules
• Small organic molecules polymerize when they
are concentrated on hot sand, clay, or rock
Protocells
• Replication and metabolism are key properties of
life
• may have been fluid-filled vesicles with a
membrane-like structure
• In water, lipids and other organic molecules can
spontaneously form vesicles with a lipid bilayer
© 2011 Pearson Education, Inc.
Self-Replicating RNA and the Dawn of
Natural Selection
• first genetic material was RNA
• RNA molecules called ribozymes have been
found to catalyze many different reactions
• Natural selection has produced self-replicating
RNA molecules
• RNA molecules that were more stable or
replicated more quickly would have left the most
descendent RNA molecules
• RNA could have provided the template for DNA, a
more stable genetic material
© 2011 Pearson Education, Inc.
The Fossil Record
• Sedimentary rocks are deposited into layers
called strata and are the richest source of fossils
• Few individuals have fossilized, and even fewer
have been discovered
• The fossil record is biased in favor of species
that
– Existed for a long time
– Were abundant and widespread
– Had hard parts
Video: Grand Canyon
© 2011 Pearson Education, Inc.
Figure 25.4
Present
Dimetrodon
Rhomaleosaurus
victor
100 mya
1m
0.5 m
4.5 cm
Coccosteus
cuspidatus
175
200
Tiktaalik
270
300
Hallucigenia
375
400
1 cm
Stromatolites
2.5 cm
500
525
Dickinsonia
costata
565
600
Fossilized
stromatolite
1,500
3,500
Tappania
How Rocks and Fossils Are Dated
• Sedimentary strata reveal the relative ages of
fossils
• The absolute ages of fossils can be determined by
radiometric dating
• A “parent” isotope decays to a “daughter” isotope
at a constant rate
• Each isotope has a known half-life, the time
required for half the parent isotope to decay
© 2011 Pearson Education, Inc.
Fraction of parent
isotope remaining
Figure 25.5
1
Accumulating
“daughter”
isotope
2
Remaining
“parent”
isotope
1
1
4
1
2
3
Time (half-lives)
8
1
4
16
Concept 25.3: Key events in life’s history
include the origins of single-celled and
multicelled organisms and the colonization
of land
• The geologic record is divided into the Archaean,
the Proterozoic, and the Phanerozoic eons
• The Phanerozoic encompasses multicellular
eukaryotic life
• The Phanerozoic is divided into three eras: the
Paleozoic, Mesozoic, and Cenozoic
© 2011 Pearson Education, Inc.
Figure 25.7-3
Cenozoic
Humans
Colonization
of land
Origin of solar
system and
Earth
Animals
Multicellular
eukaryotes
4
1
Proterozoic
2
Archaean
3
Prokaryotes
Single-celled
eukaryotes
Atmospheric oxygen
The First Single-Celled Organisms
• The oldest known fossils are stromatolites, rocks
formed by the accumulation of sedimentary layers
on bacterial mats
• Stromatolites date back 3.5 billion years ago
• Prokaryotes were Earth’s sole inhabitants from 3.5
to about 2.1 billion years ago
© 2011 Pearson Education, Inc.
Photosynthesis and the Oxygen Revolution
• Most atmospheric oxygen (O2) is of biological
origin
• O2 produced by oxygenic photosynthesis reacted
with dissolved iron and precipitated out to form
banded iron formations
© 2011 Pearson Education, Inc.
• By about 2.7 billion years ago, O2 began
accumulating in the atmosphere and rusting ironrich terrestrial rocks
• This “oxygen revolution” from 2.7 to 2.3 billion
years ago caused the extinction of many
prokaryotic groups
• Some groups survived and adapted using cellular
respiration to harvest energy
© 2011 Pearson Education, Inc.
Atmospheric O2
(percent of present-day levels; log scale)
Figure 25.8
1,000
100
10
1
0.1
“Oxygen
revolution”
0.01
0.001
0.0001
4
3
2
Time (billions of years ago)
1
0
• The early rise in O2 was likely caused by ancient
cyanobacteria
• A later increase in the rise of O2 might have been
caused by the evolution of eukaryotic cells
containing chloroplasts
© 2011 Pearson Education, Inc.
The First Eukaryotes
• The oldest fossils of eukaryotic cells date back 2.1
billion years
• Eukaryotic cells have a nuclear envelope,
mitochondria, endoplasmic reticulum, and a
cytoskeleton
• The endosymbiont theory proposes that
mitochondria and plastids (chloroplasts and
related organelles) were formerly small
prokaryotes living within larger host cells
• An endosymbiont is a cell that lives within a host
cell
© 2011 Pearson Education, Inc.
Figure 25.9-3
Plasma membrane
Cytoplasm
DNA
Ancestral
prokaryote
Nucleus
Endoplasmic
reticulum
Photosynthetic
prokaryote
Mitochondrion
Nuclear envelope
Aerobic heterotrophic
prokaryote
Mitochondrion
Plastid
Ancestral
heterotrophic eukaryote
Ancestral photosynthetic
eukaryote
• Key evidence supporting an endosymbiotic origin
of mitochondria and plastids:
– Inner membranes are similar to plasma
membranes of prokaryotes
– Division is similar in these organelles and some
prokaryotes
– These organelles transcribe and translate their
own DNA
– Their ribosomes are more similar to prokaryotic
than eukaryotic ribosomes
© 2011 Pearson Education, Inc.
The Origin of Multicellularity
• The evolution of eukaryotic cells allowed for a
greater range of unicellular forms
• A second wave of diversification occurred when
multicellularity evolved and gave rise to algae,
plants, fungi, and animals
© 2011 Pearson Education, Inc.
The Colonization of Land
• Fungi, plants, and animals began to colonize land
about 500 million years ago
• Vascular tissue in plants transports materials
internally and appeared by about 420 million years
ago
• Plants and fungi today form mutually beneficial
associations and likely colonized land together
• Arthropods and tetrapods are the most
widespread and diverse land animals
• Tetrapods evolved from lobe-finned fishes around
365 million years ago
© 2011 Pearson Education, Inc.
Plate Tectonics
• Land masses of Earth have formed a
supercontinent: 1.1 billion, 600 million, and 250
million years ago
• Tectonic plates move slowly through the process
of continental drift
– Oceanic and continental plates can collide, separate, or
slide past each other
– mountains and islands, and earthquakes
© 2011 Pearson Education, Inc.
Figure 25.13
North
American
Plate
Juan de Fuca
Plate
Eurasian Plate
Caribbean
Plate
Philippine
Plate
Arabian
Plate
Indian
Plate
Cocos Plate
Pacific
Plate
Nazca
Plate
South
American
Plate
Scotia Plate
African
Plate
Antarctic
Plate
Australian
Plate
Consequences of Continental Drift
• Formation of the supercontinent Pangaea about
250 million years ago had many effects
– A deepening of ocean basins
– A reduction in shallow water habitat
– A colder and drier climate inland
• most species that have ever lived are now extinct
• Mass extinction is the result of disruptive global
environmental changes
• In each of the five mass extinction events, more
than 50% of Earth’s species became extinct
© 2011 Pearson Education, Inc.
Figure 25.15
1,100
1,000
25
800
20
700
600
15
500
400
10
300
200
5
100
Era
Period
0
E
542
O
Paleozoic
D
S
488 444 416
359
Mesozoic
P
C
299
Tr
251
J
200
Cenozoic
C
145
P
65.5
0
Q
N
0
Number of families:
Total extinction rate
(families per million years):
900
• Permian extinction: 251 million years ago
– extinction of about 96% of marine animal species
• Intense volcanism in what is now Siberia
• Global warming resulting from the emission of
large amounts of CO2 from the volcanoes
• Reduced temperature gradient from equator to
poles
• Oceanic anoxia from reduced mixing of ocean
waters
© 2011 Pearson Education, Inc.
• Cretaceous mass extinction: 65.5 million years
– half of all marine species and many terrestrial plants
and animals, including most dinosaurs
• iridium in sedimentary rocks suggests a meteorite
• Dust clouds blocked sunlight and disturbed global
climate
• The Chicxulub crater off the coast of Mexico is
evidence of a meteorite that dates to the same
time
© 2011 Pearson Education, Inc.
Adaptive Radiations
• Adaptive radiation is the evolution of diversely
adapted species from a common ancestor
• Adaptive radiations may follow
– Mass extinctions
– The evolution of novel characteristics
– The colonization of new regions
• Mammals underwent an adaptive radiation after
the extinction of terrestrial dinosaurs
© 2011 Pearson Education, Inc.
Changes in Rate and Timing
• Heterochrony evolutionary change in the rate or
timing of developmental events
– It can have a significant impact on body shape
• Paedomorphosis, the rate of reproductive
development accelerates compared with somatic
development
– The sexually mature species may retain body features
that were previous juvenile structures
Animation: Allometric Growth
© 2011 Pearson Education, Inc.
Figure 25.21
Chimpanzee infant
Chimpanzee adult
Chimpanzee fetus
Chimpanzee adult
Human fetus
Human adult
Figure 25.22
Gills
Changes in Spatial Pattern
• Homeotic genes: control the placement and organization
of body parts
• Hox genes: class of homeotic genes that provide positional
information during development
– If Hox genes are expressed in the wrong location, body
parts can be produced in the wrong location
• Specific changes in the Ubx gene have been identified that
can “turn off” leg development
© 2011 Pearson Education, Inc.
Figure 25.24
Hox gene 6
Hox gene 7
Hox gene 8
Ubx
About 400 mya
Drosophila
Artemia
Evolutionary Novelties
• Most novel biological structures evolve in many
stages from previously existing structures
• Complex eyes have evolved from simple
photosensitive cells independently many times
• Exaptations are structures that evolve in one
context but become co-opted for a different
function
• Natural selection can only improve a structure in
the context of its current utility
© 2011 Pearson Education, Inc.
Figure 25.26
(a) Patch of pigmented cells
(b) Eyecup
Pigmented cells
(photoreceptors)
Pigmented
cells
Epithelium
Nerve fibers
Nerve fibers
(c) Pinhole camera-type eye
(d) Eye with primitive lens
Epithelium
Cellular
mass
(lens)
Fluid-filled
cavity
(e) Complex camera lens-type eye
Cornea
Cornea
Lens
Retina
Optic
nerve
Pigmented
layer
(retina)
Optic nerve
Optic nerve
LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 26
Phylogeny and the Tree of Life
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
• Phylogeny: evolutionary history of a species or
related species
• Systematics: classifies organisms and
determines their evolutionary relationships
– fossil, molecular, and genetic data
• Taxonomy is the ordered division and
naming of organisms
© 2011 Pearson Education, Inc.
Binomial Nomenclature
• Linnaeus (18th Century) taxonomy based on
resemblances
– two-part names for species and hierarchical
classification
• Genus: first part of the name
– The first letter is capitalized
• specific epithet : second part is unique for each
species within the genus
• Entire species name is italicized
• Taxon: a taxonomic unit
– domain, kingdom, phylum, class, order, family,
genus, and species
© 2011 Pearson Education, Inc.
Figure 26.3
Species:
Panthera pardus
Genus:
Panthera
Family:
Felidae
Order:
Carnivora
Class:
Mammalia
Phylum:
Chordata
Domain:
Bacteria
Kingdom:
Animalia
Domain:
Eukarya
Domain:
Archaea
Linking Classification and Phylogeny
• Phylogenetic Tree: evolutionary relationships in branching trees
– hypothesis about evolutionary relationships
– Each branch represents the divergence of two species
• Systematists have proposed the PhyloCode,
– Only recognizes groups with a common ancestor and its
descendents
• Sister taxa: groups with immediate common ancestor
• rooted tree: a branch to represent the last common ancestor
• basal taxon: diverges early in the group history and originates
near the common ancestor
• Polytomy: branch from which more than two groups emerge
© 2011 Pearson Education, Inc.
Figure 26.4
Order
Family Genus
Species
Panthera
Felidae
Panthera
pardus
(leopard)
Taxidea
Lutra
Mustelidae
Carnivora
Taxidea
taxus
(American
badger)
Lutra lutra
(European
otter)
Canis
Canidae
Canis
latrans
(coyote)
Canis
lupus
(gray wolf)
Figure 26.5
Branch point:
where lineages diverge
Taxon A
Taxon B
Taxon C
Sister
taxa
Taxon D
ANCESTRAL
LINEAGE
Taxon E
Taxon F
Taxon G
This branch point
represents the
common ancestor of
taxa A–G.
This branch point forms a
polytomy: an unresolved
pattern of divergence.
Basal
taxon
What We Can and Cannot Learn from
Phylogenetic Trees
• Phylogenetic trees show patterns of descent, not
phenotypic similarity
• Phylogenetic trees do not indicate when species
evolved or how much change occurred in a
lineage
• It should not be assumed that a taxon evolved
from the taxon next to it
© 2011 Pearson Education, Inc.
Phylogenies are inferred from
morphological and molecular data
• Homologies: phenotypic and genetic similarities
due to shared ancestry
– Organisms with similar morphologies or DNA
sequences are likely to be related
• In phylogeny, must distinguish whether a similarity
is the result of:
– Homology is similarity due to shared ancestry
– Analogy is similarity due to convergent evolution
• similar environmental pressures/ natural selection produce
similar adaptations in different evolutionary lineages
© 2011 Pearson Education, Inc.
Figure 26.7
• Bat and bird wings are homologous as forelimbs,
but analogous as functional wings
• Analogous structures or molecular sequences that
evolved independently are also called
homoplasies
• Homology can be distinguished from analogy by
comparing fossil evidence and the degree of
complexity
• The more complex two similar structures are, the
more likely it is that they are homologous
• Molecular systematics uses DNA and other
molecular data to determine evolutionary
relationships
© 2011 Pearson Education, Inc.
Concept 26.3: Shared characters are used
to construct phylogenetic trees
• Cladistics: group organisms by common descent
– Clade: group of species that includes an ancestral
species and all its descendants
– A valid clade is monophyletic, signifying that it consists
of the ancestor species and all its descendants
– A paraphyletic grouping consists of an ancestral
species and some, but not all, of the descendants
– A polyphyletic grouping consists of various species
with different ancestors
© 2011 Pearson Education, Inc.
Figure 26.10
(a) Monophyletic group (clade)
(b) Paraphyletic group
(c) Polyphyletic group
A
A
B
B
C
C
C
D
D
D
E
E
F
F
F
G
G
G
A
B
Group 
Group 
E
Group 
Shared Ancestral and Shared Derived
Characters
• A shared ancestral character: character that
originated in a taxon ancestor
• A shared derived character: evolutionary novelty
unique to a particular clade
• In some trees, the length of a branch can reflect
the number of genetic changes that have taken
place in a particular DNA sequence
• In other trees, branch length can represent
chronological time, and branching points can be
determined from the fossil record
© 2011 Pearson Education, Inc.
Figure 26.11
Lancelet
(outgroup)
CHARACTERS
Lancelet
(outgroup)
Lamprey
Bass
Frog
Turtle
Leopard
TAXA
Lamprey
0
1
1
1
1
1
Bass
Vertebral
column
(backbone)
Hinged jaws
0
0
1
1
1
1
Four walking
legs
0
0
0
1
1
1
Amnion
0
0
0
0
1
1
Hair
0
0
0
0
0
1
Vertebral
column
Frog
Hinged jaws
Turtle
Four walking legs
Amnion
Leopard
Hair
(a) Character table
(b) Phylogenetic tree
Figure 26.13
Drosophila
Lancelet
Zebrafish
Frog
Chicken
Human
Mouse
PALEOZOIC
542
MESOZOIC
251
Millions of years ago
CENOZOIC
65.5
Present
• Maximum parsimony assumes that the tree that
requires the fewest evolutionary events is the most
likely
• maximum likelihood: given certain rules about
how DNA changes over time, a tree can be found
that reflects the most likely sequence of
evolutionary events
• Computer programs are used to search for trees
that are parsimonious and likely
© 2011 Pearson Education, Inc.
Figure 26.14
Human
Mushroom
Tulip
0
30%
40%
0
40%
Human
Mushroom
Tulip
0
(a) Percentage differences between sequences
15%
5%
5%
15%
15%
10%
25%
20%
Tree 1: More likely
Tree 2: Less likely
(b) Comparison of possible trees
Phylogenetic Trees as Hypotheses
• The best phylogenetic trees fits the most data:
morphological, molecular, and fossil
• Phylogenetic bracketing allows us to predict
features of an ancestor from features of its
descendants
– Birds and crocodiles share several features: fourchambered hearts, song, nest building, and brooding
– The fossil record supports nest building and brooding in
dinosaurs
© 2011 Pearson Education, Inc.
Figure 26.16
Lizards
and snakes
Crocodilians
Common
ancestor of
crocodilians,
dinosaurs,
and birds
Ornithischian
dinosaurs
Saurischian
dinosaurs
Birds
Concept 26.4: An organism’s evolutionary
history is documented in its genome
• DNA that codes for rRNA changes relatively slowly
and is useful for investigating branching points
hundreds of millions of years ago
• mtDNA evolves rapidly and can be used to explore
recent evolutionary events
© 2011 Pearson Education, Inc.
• Gene duplication increases the number of genes
in the genome, providing more opportunities for
evolutionary changes
– Repeated gene duplications result in gene families
– traced to a common ancestor
• Orthologous genes are found in a single copy in
the genome and are homologous between species
– diverge only after speciation
• Paralogous genes result from gene duplication,
so are found in more than one copy in the genome
– diverge within the clade that carries them and often
evolve new functions
© 2011 Pearson Education, Inc.
Figure 26.18
Formation of orthologous genes:
a product of speciation
Species A
Formation of paralogous genes:
within a species
Ancestral gene
Ancestral gene
Ancestral species
Species C
Speciation with
divergence of gene
Gene duplication and divergence
Orthologous genes
Paralogous genes
Species C after many generations
Species B
Genome Evolution
• Orthologous genes are widespread and extend across
many widely varied species
– For example, humans and mice diverged about 65
million years ago, and 99% of our genes are
orthologous
• Gene number and the complexity of an organism are not
strongly linked
– For example, humans have only four times as many
genes as yeast, a single-celled eukaryote
• Genes in complex organisms appear to be very
versatile, and each gene can perform many functions
© 2011 Pearson Education, Inc.
Concept 26.5: Molecular clocks help track
evolutionary time
• A molecular clock uses constant rates of evolution in
some genes to estimate the absolute time of
evolutionary change
– orthologous genes: nucleotide substitutions are
proportional to the time of the last common ancestor
– paralogous genes: nucleotide substitutions are
proportional to the time gene duplication
• Molecular clocks are calibrated against branches whose
dates are known from the fossil record
• Individual genes vary in how clocklike they are
© 2011 Pearson Education, Inc.
Neutral Theory
• much evolutionary change in genes and proteins has no
effect on fitness and is not influenced by natural
selection
• the rate of molecular change in these genes and
proteins should be regular like a clock
– The molecular clock does not run as smoothly as neutral theory
predicts
– Irregularities result from natural selection in which some DNA
changes are favored over others
– Estimates of evolutionary divergences older than the fossil
record have a high degree of uncertainty
– The use of multiple genes may improve estimates
© 2011 Pearson Education, Inc.
Applying a Molecular Clock: The Origin
of HIV
• Phylogenetic analysis shows that HIV is
descended from viruses that infect chimpanzees
and other primates
• HIV spread to humans more than once
• Comparison of HIV samples shows that the virus
evolved in a very clocklike way
• Application of a molecular clock to one strain of
HIV suggests that that strain spread to humans
during the 1930s
© 2011 Pearson Education, Inc.
Figure 26.20
Index of base changes between HIV gene sequences
0.20
0.15
HIV
0.10
Range
Adjusted best-fit line
(accounts for uncertain
dates of HIV sequences)
0.05
0
1900
1920
1940
1960
Year
1980
2000
From Two Kingdoms to Three Domains
• Early taxonomists: plants or animals
• Five kingdoms: Monera (prokaryotes), Protista,
Plantae, Fungi, and Animalia
• Three-domains: Bacteria, Archaea, and Eukarya
– tree of life: eukaryotes and archaea are more closely
related to each other than to bacteria
– tree of life is based largely on rRNA genes, as these
have evolved slowly
Animation: Classification Schemes
© 2011 Pearson Education, Inc.
Figure 26.21
Eukarya
Land plants
Green algae
Cellular slime molds
Dinoflagellates
Forams
Ciliates
Red algae
Diatoms
Amoebas
Euglena
Trypanosomes
Leishmania
Animals
Fungi
Green
nonsulfur bacteria
Sulfolobus
Thermophiles
(Mitochondrion)
Spirochetes
Halophiles
COMMON
ANCESTOR
OF ALL
LIFE
Methanobacterium
Archaea
Chlamydia
Green
sulfur bacteria
Bacteria
Cyanobacteria
(Plastids, including
chloroplasts)
• Horizontal gene transfer is the movement of
genes from one genome to another
– exchange of transposable elements and plasmids, viral
infection, and fusion of organisms
• Some researchers suggest that eukaryotes arose
as an fusion between a bacterium and archaean
• If so, early evolutionary relationships might be
better depicted by a ring of life instead of a tree of
life
© 2011 Pearson Education, Inc.