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CAMPBELL
BIOLOGY Reece • Urry • Cain • Wasserman • Minorsky • Jackson
© 2014 Pearson Education, Inc.
TENTH
EDITION
25 The History of
Life on Earth
Lecture Presentation by
Nicole Tunbridge and
Kathleen Fitzpatrick
© 2014 Pearson Education, Inc.
Lost Worlds
Past organisms were very different from those
now alive
The fossil record shows macroevolutionary
changes over large time scales, for example
The emergence of terrestrial vertebrates
The impact of mass extinctions
The origin of flight in birds
© 2014 Pearson Education, Inc.
Figure 25.1
© 2014 Pearson Education, Inc.
Figure 25.1a
Cryolophosaurus skull
© 2014 Pearson Education, Inc.
Concept 25.1: Conditions on early Earth made the origin of life possible
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
© 2014 Pearson Education, Inc.
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 about 4 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)
© 2014 Pearson Education, Inc.
In the 1920s, A. I. Oparin and J. B. S. Haldane
hypothesized that the early atmosphere was a
reducing environment
In 1953, Stanley Miller and Harold Urey conducted
lab experiments that showed that the abiotic
synthesis of organic molecules in a reducing
atmosphere is possible
© 2014 Pearson Education, Inc.
However, the evidence is not yet convincing that
the early atmosphere was in fact reducing
Instead of forming in the atmosphere, the first
organic compounds may have been synthesized
near volcanoes or deep-sea vents
Miller-Urey-type experiments demonstrate that
organic molecules could have formed with various
possible atmospheres
© 2014 Pearson Education, Inc.
Figure 25.2
1953 2008 2008 1953 0
100
200 20
10
0
Nu
mb
er
of
am
ino
ac
ids
Mas
s o
f am
ino
ac
ids (
mg
)
© 2014 Pearson Education, Inc.
Figure 25.3
1 m
m
© 2014 Pearson Education, Inc.
Figure 25.3a
© 2014 Pearson Education, Inc.
Figure 25.3b
1 m
m
© 2014 Pearson Education, Inc.
Video: Tube Worms
© 2014 Pearson Education, Inc.
Amino acids have also been found in meteorites
© 2014 Pearson Education, Inc.
Abiotic Synthesis of Macromolecules
RNA monomers have been produced
spontaneously from simple molecules
Small organic molecules polymerize when they
are concentrated on hot sand, clay, or rock
© 2014 Pearson Education, Inc.
Protocells
Replication and metabolism are key properties of
life and may have appeared together in protocells
Protocells may have formed from fluid-filled
vesicles with a membrane-like structure
In water, lipids and other organic molecules can
spontaneously form vesicles with a lipid bilayer
© 2014 Pearson Education, Inc.
Adding clay can increase the rate of vesicle
formation
Vesicles exhibit simple reproduction and
metabolism and maintain an internal chemical
environment
© 2014 Pearson Education, Inc.
Figure 25.4
(a) Self-assembly
Time (minutes)
Precursor molecules plus
montmorillonite clay
Precursor
molecules only
60 40 20 0 0
0.2
0.4
Rela
tive t
urb
idit
y, an
ind
ex o
f vesic
le n
um
ber
(b) Reproduction (c) Absorption of RNA
Vesicle boundary 1 µm 10 µm
© 2014 Pearson Education, Inc.
Figure 25.4a
(a) Self-assembly
Time (minutes)
Precursor molecules plus montmorillonite clay
Precursor molecules only
60 40 20 0 0
0.2
0.4 R
ela
tive t
urb
idit
y, a
n
ind
ex o
f vesic
le n
um
ber
© 2014 Pearson Education, Inc.
Figure 25.4b
(b) Reproduction
10 µm
© 2014 Pearson Education, Inc.
Figure 25.4c
(c) Absorption of RNA
Vesicle boundary 1 µm
© 2014 Pearson Education, Inc.
Self-Replicating RNA
The first genetic material was probably RNA, not
DNA
RNA molecules called ribozymes have been
found to catalyze many different reactions
For example, ribozymes can make complementary
copies of short stretches of RNA
© 2014 Pearson Education, Inc.
Natural selection has produced self-replicating
RNA molecules
RNA molecules that were more stable or
replicated more quickly would have left the most
descendant RNA molecules
The early genetic material might have formed an
“RNA world”
© 2014 Pearson Education, Inc.
Vesicles containing RNA capable of replication
would have been protocells
RNA could have provided the template for DNA, a
more stable genetic material
© 2014 Pearson Education, Inc.
Concept 25.2: The fossil record documents the history of life
The fossil record reveals changes in the history of
life on Earth
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The Fossil Record
Sedimentary rocks are deposited into layers called
strata and are the richest source of fossils
The fossil record shows changes in kinds of
organisms on Earth over time
© 2014 Pearson Education, Inc.
Figure 25.5
Rhomaleosaurus victor
Tiktaalik
Dickinsonia costata
Hallucigenia
Tappania
Present
100 mya
175
200
270 300
375
400
500 510
560
600
1,500
3,500
Dimetrodon
Coccosteus cuspidatus
Stromatolites
1 m
2.5
cm
1 cm
4.5 cm
0.5 m
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Figure 25.5a
Stromatolite cross section
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Figure 25.5b
Stromatolites
© 2014 Pearson Education, Inc.
Figure 25.5c
Tappania
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Figure 25.5d
Dickinsonia costata
2.5
cm
© 2014 Pearson Education, Inc.
Figure 25.5e
1 cm
Hallucigenia
© 2014 Pearson Education, Inc.
Figure 25.5f
Coccosteus cuspidatus
4.5 cm
© 2014 Pearson Education, Inc.
Figure 25.5g
Tiktaalik
© 2014 Pearson Education, Inc.
Figure 25.5h
Dimetrodon
0.5 m
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Figure 25.5i
Rhomaleosaurus victor
1 m
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Video: Grand Canyon
© 2014 Pearson Education, Inc.
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
© 2014 Pearson Education, Inc.
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 radioactive “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
© 2014 Pearson Education, Inc.
Figure 25.6
Accumulating
“daughter”
isotope
Remaining
“parent”
isotope
Time (half-lives)
4 3 2 1
1 4
8 1
1 2
16 1 F
racti
on
of
pare
nt
iso
top
e r
em
ain
ing
© 2014 Pearson Education, Inc.
Radiocarbon dating can be used to date fossils up
to 75,000 years old
For older fossils, some isotopes can be used to
date volcanic rock layers above and below the
fossil
© 2014 Pearson Education, Inc.
The Origin of New Groups of Organisms
Mammals belong to the group of animals called
tetrapods
The evolution of unique mammalian features can
be traced through gradual changes over time
© 2014 Pearson Education, Inc.
Figure 25.7
OTHER
TETRA-
PODS
Synapsid (300 mya)
Later cynodont (220 mya)
Early cynodont (260 mya)
Very late cynodont (195 mya)
Therapsid (280 mya)
Key to skull bones
Articular
Quadrate
Dentary
Squamosal
Hinge
Original hinge
Temporal
fenestra
(partial view)
Mammals
†
† Very late (non-
mammalian)
cynodonts
Dimetrodon
Reptiles (including dinosaurs and birds)
Syn
ap
sid
s
Th
era
psid
s
Cyn
od
on
ts
Temporal fenestra
Temporal fenestra
Hinge
Hinge Hinge
New hinge
© 2014 Pearson Education, Inc.
Figure 25.7a
OTHER
TETRA-
PODS
Mammals
† Very late (non-
mammalian)
cynodonts
Dimetrodon
Reptiles (including dinosaurs and birds)
Syn
ap
sid
s
Th
era
ps
ids
Cyn
od
on
ts
†
© 2014 Pearson Education, Inc.
Figure 25.7b
Synapsid (300 mya)
Therapsid (280 mya)
Temporal fenestra
Temporal fenestra
Hinge
Hinge
Key to skull bones
Articular
Quadrate
Dentary
Squamosal
© 2014 Pearson Education, Inc.
Figure 25.7c
Later cynodont (220 mya)
Early cynodont (260 mya)
Very late cynodont (195 mya)
Key to skull bones Articular
Quadrate Dentary Squamosal
Hinge
Original hinge
Temporal fenestra (partial view)
Hinge
New hinge
© 2014 Pearson Education, Inc.
Concept 25.3: Key events in life’s history include the origins of unicellular and multicellular organisms and the colonization of land
The geologic record is divided into the Hadean,
Archaean, Proterozoic, and Phanerozoic eons
The Phanerozoic eon includes the last half billion
years
The Phanerozoic is divided into three eras: the
Paleozoic, Mesozoic, and Cenozoic
© 2014 Pearson Education, Inc.
Table 25.1
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Table 25.1a
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Table 25.1b
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Major boundaries between eras correspond to
major extinction events in the fossil record
© 2014 Pearson Education, Inc.
Figure 25.8-1
Origin of solar system and Earth
Prokaryotes
Atmospheric oxygen
Hadean
Archaean
4
3
© 2014 Pearson Education, Inc.
Figure 25.8-2
Origin of solar system and Earth
Prokaryotes
Atmospheric oxygen
Hadean
Archaean
4
3
Proterozoic
Animals
Multicellular eukaryotes
Single-celled eukaryotes
2
1
© 2014 Pearson Education, Inc.
Figure 25.8-3
Origin of solar system and Earth
Prokaryotes
Atmospheric oxygen
Hadean
Archaean
4
3
Proterozoic
Animals
Multicellular eukaryotes
Single-celled eukaryotes
2
1
Colonization of land
Humans
© 2014 Pearson Education, Inc.
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 for more
than 1.5 billion years
© 2014 Pearson Education, Inc.
Figure 25.UN01
Prokaryotes
4
3
1
2
© 2014 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
© 2014 Pearson Education, Inc.
Figure 25.UN02
Atmospheric oxygen
4
3
1
2
© 2014 Pearson Education, Inc.
By about 2.7 billion years ago, O2 began
accumulating in the atmosphere and rusting iron-
rich 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
© 2014 Pearson Education, Inc.
Figure 25.9
1,000
100
10
1
0.1
0.01
0.001
0.0001
Time (billions of years ago)
“Oxygen revolution”
0 1 2 3 4
Atm
os
ph
eri
c O
2
(pe
rce
nt
of
pre
se
nt-
da
y le
ve
ls;
log
scale
)
© 2014 Pearson Education, Inc.
The First Eukaryotes
The oldest fossils of eukaryotic cells date back
1.8 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
© 2014 Pearson Education, Inc.
Figure 25.UN03
Single- celled eukaryotes
4
3
1
2
© 2014 Pearson Education, Inc.
The prokaryotic ancestors of mitochondria and
plastids probably gained entry to the host cell as
undigested prey or internal parasites
In the process of becoming more interdependent,
the host and endosymbionts would have become
a single organism
Serial endosymbiosis supposes that
mitochondria evolved before plastids through a
sequence of endosymbiotic events
© 2014 Pearson Education, Inc.
Figure 25.10-1
Cytoplasm
DNA
Nucleus
Nuclear envelope
Endoplasmic reticulum
Plasma membrane
Ancestral prokaryote
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Figure 25.10-2
Cytoplasm
DNA
Nucleus
Nuclear envelope
Endoplasmic reticulum
Plasma membrane
Ancestral prokaryote
Engulfed aerobic bacterium
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Figure 25.10-3
Cytoplasm
DNA
Nucleus
Nuclear envelope
Endoplasmic reticulum
Plasma membrane
Ancestral prokaryote
Ancestral heterotrophic eukaryote
Mitochondrion
Engulfed aerobic bacterium
© 2014 Pearson Education, Inc.
Figure 25.10-4
Cytoplasm
DNA
Nucleus
Nuclear envelope
Endoplasmic reticulum
Plasma membrane
Ancestral prokaryote
Ancestral heterotrophic eukaryote
Ancestral photosynthetic eukaryote
Mitochondrion
Mito- chondrion
Engulfed photo- synthetic bacterium
Engulfed aerobic bacterium
Plastid
© 2014 Pearson Education, Inc.
Key evidence supporting an endosymbiotic origin
of mitochondria and plastids
Inner membranes are similar to plasma membranes
of prokaryotes
Division and DNA structure 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
© 2014 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
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Early Multicellular Eukaryotes
The oldest known fossils of multicellular
eukaryotes that can be resolved taxonomically are
of small algae that lived about 1.2 billion years ago
Older fossils, dating to 1.8 billion years ago, may
also be small, multicellular eukaryotes
The Ediacaran biota were an assemblage of larger
and more diverse soft-bodied organisms that lived
from 600 to 535 million years ago
© 2014 Pearson Education, Inc.
Figure 25.UN04
Multicellular eukaryotes
4
3
1
2
© 2014 Pearson Education, Inc.
The Cambrian Explosion
The Cambrian explosion refers to the sudden
appearance of fossils resembling modern animal
phyla in the Cambrian period (535 to 525 million
years ago)
A few animal phyla appear even earlier: sponges,
cnidarians, and molluscs
The Cambrian explosion provides the first
evidence of predator-prey interactions
© 2014 Pearson Education, Inc.
Figure 25.UN05
Animals
4
3
1
2
© 2014 Pearson Education, Inc.
Figure 25.11
Sponges
Cnidarians
Echinoderms
Chordates
Brachiopods
Annelids
Molluscs
Arthropods
PROTEROZOIC PALEOZOIC
Ediacaran Cambrian
635 605 575 545 515 485 0
Time (millions of years ago)
© 2014 Pearson Education, Inc.
DNA analyses suggest that sponges and the
common ancestor to several other animal phyla
evolved 700 to 670 million years ago
Fossil evidence of early animals dates back to 710
to 560 million years ago
Molecular and fossil data suggest that “the
Cambrian explosion had a long fuse”
© 2014 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
© 2014 Pearson Education, Inc.
Figure 25.UN06
Colonization of land
4
3
1
2
© 2014 Pearson Education, Inc.
Plants and fungi likely colonized land together
Fossilized plants show evidence of mutually
beneficial associations with fungi (mycorrhizae)
that are still seen today
© 2014 Pearson Education, Inc.
Figure 25.12
Zone of arbuscule- containing cells
100 n
m
© 2014 Pearson Education, Inc.
Figure 25.12a
Zone of arbuscule- containing cells
100 n
m
© 2014 Pearson Education, Inc.
Figure 25.12b
© 2014 Pearson Education, Inc.
Arthropods and tetrapods are the most
widespread and diverse land animals
Tetrapods evolved from lobe-finned fishes around
365 million years ago
The human lineage of tetrapods evolved around
6–7 million years ago, and modern humans
originated only 195,000 years ago
© 2014 Pearson Education, Inc.
Concept 25.4: The rise and fall of groups of organisms reflect differences in speciation and extinction rates
The history of life on Earth has seen the rise and
fall of many groups of organisms
The rise and fall of groups depends on speciation
and extinction rates within the group
© 2014 Pearson Education, Inc.
Figure 25.13
Common ancestor of lineages A and B
Lin
eag
e A
L
ine
ag
e B
†
†
†
†
†
†
3 2 4 1 0 Millions of years ago
© 2014 Pearson Education, Inc.
Plate Tectonics
The land masses of Earth have formed a
supercontinent three times over the past 1.5 billion
years: 1.1 billion, 600 million, and 250 million
years ago
According to the theory of plate tectonics, Earth’s
crust is composed of plates floating on Earth’s
mantle
© 2014 Pearson Education, Inc.
Figure 25.14
Crust
Mantle
Outer core
Inner core
© 2014 Pearson Education, Inc.
Tectonic plates move slowly through the process
of continental drift
Oceanic and continental plates can collide,
separate, or slide past each other
Interactions between plates cause the formation of
mountains and islands, and earthquakes
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Figure 25.15
Juan de Fuca Plate
North American Plate
Eurasian Plate
Arabian Plate
Philippine Plate
Australian Plate
Indian Plate
African Plate
Antarctic Plate
Scotia Plate
South American Plate Nazca
Plate
Pacific Plate
Cocos Plate
Caribbean Plate
© 2014 Pearson Education, Inc.
Video: Lava Flow
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Video: Volcanic Eruption
© 2014 Pearson Education, Inc.
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
© 2014 Pearson Education, Inc.
Figure 25.16
Present
45 mya
65.5 mya
135 mya
251 mya The supercontinent Pangaea
Laurasia and Gondwana landmasses
Present-day continents
Collision of India with Eurasia
Ce
no
zo
ic
Me
so
zo
ic
Pa
leo
zo
ic
Laurasia
Antarctica
Eurasia
Africa India South
America Madagascar
© 2014 Pearson Education, Inc.
Figure 25.16a
135 mya
251 mya The supercontinent Pangaea
Laurasia and Gondwana landmasses
Me
so
zo
ic
Laurasia
Pa
leo
zo
ic
© 2014 Pearson Education, Inc.
Figure 25.16b
Present
45 mya
65.5 mya Present-day continents
Collision of India with Eurasia
Cen
ozo
ic
Antarctica
Eurasia
Africa India South
America Madagascar
© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
Animation: The Geologic Record
© 2014 Pearson Education, Inc.
Plate tectonics has many effects on living
organisms
A continent’s climate can change as the plate it is
on moves north or south
Separation of land masses can lead to allopatric
speciation
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Mass Extinctions
The fossil record shows that most species that
have ever lived are now extinct
Extinction can be caused by changes to a species’
environment
At times, the rate of extinction has increased
dramatically and caused a mass extinction
Mass extinction is the result of disruptive global
environmental changes
© 2014 Pearson Education, Inc.
The “Big Five” Mass Extinction Events
In each of the five mass extinction events, 50% or
more of marine species became extinct
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Figure 25.17
1,100
1,000
900
800
700
600
500
400
300
200
100
0
0 65.5 145 200 251 299 359 416 444 488 542
Era
Period C O S D C P T J C P N Q Cenozoic Mesozoic Paleozoic
Time (mya)
To
tal e
xti
nc
tio
n r
ate
(f
am
ilie
s p
er
millio
n y
ea
rs):
Nu
mb
er
of
fam
ilie
s:
0
5
10
15
20
25
© 2014 Pearson Education, Inc.
The Permian extinction defines the boundary
between the Paleozoic and Mesozoic eras 251
million years ago
This mass extinction occurred in less than 500,000
years and caused the extinction of about 96% of
marine animal species
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A number of factors might have contributed to
these extinctions
Intense volcanism in what is now Siberia
Global warming and ocean acidification resulting
from the emission of large amounts of CO2 from the
volcanoes
Anoxic conditions resulting from nutrient enrichment
of ecosystems
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The Cretaceous mass extinction occurred 65.5
million years ago
Organisms that went extinct include about half of
all marine species and many terrestrial plants and
animals, including most dinosaurs
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The presence of iridium in sedimentary rocks
suggests a meteorite impact about 65 million
years ago
Dust clouds caused by the impact would have
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
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Figure 25.18
NORTH
AMERICA
Yucatán
Peninsula
Chicxulub
crater
© 2014 Pearson Education, Inc.
Is a Sixth Mass Extinction Under Way?
Scientists estimate that the current rate of
extinction is 100 to 1,000 times the typical
background rate
Extinction rates tend to increase when global
temperatures increase
Data suggest that a sixth, human-caused mass
extinction is likely to occur unless dramatic action
is taken
© 2014 Pearson Education, Inc.
Figure 25.19
Relative temperature
Mass extinctions 3
2
1
0
−1
−2 −2 −1 −3 0 1 2 3 4
Warmer Cooler
Rela
tive e
xti
ncti
on
rate
of
mari
ne
an
imal
ge
ne
ra
© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
Consequences of Mass Extinctions
Mass extinction can alter ecological communities
and the niches available to organisms
It can take from 5 to 100 million years for diversity
to recover following a mass extinction
Mass extinctions can change the types of
organisms found in ecological communities
For example, the percentage of marine organisms
that were predators increased after the Permian
and Cretaceous mass extinctions
© 2014 Pearson Education, Inc.
Figure 25.20
Permian mass
extinction
Cretaceous
mass extinction
Mesozoic Paleozoic Cenozoic
C P N J T P C D S O C
542 488 444 416 359 299 251 200
Time (mya)
145 65.
5
0 Q
Era
Period
0
10
20
30
40
50
Pre
da
tor
ge
ne
ra (
%)
© 2014 Pearson Education, Inc.
Lineages with novel and advantageous features
can be lost during mass extinctions
By eliminating so many species, mass extinctions
can pave the way for adaptive radiations
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Adaptive Radiations
Adaptive radiation is the rapid 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
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Worldwide Adaptive Radiations
Mammals underwent an adaptive radiation after
the extinction of terrestrial dinosaurs
The disappearance of dinosaurs (except birds)
allowed for the expansion of mammals in diversity
and size
Other notable radiations include photosynthetic
prokaryotes, large predators in the Cambrian, land
plants, insects, and tetrapods
© 2014 Pearson Education, Inc.
Figure 25.21
Ancestral
mammal
ANCESTRAL
CYNODONT
Monotremes
(5 species)
Marsupials
(324 species)
Eutherians
(placental
mammals;
5,010 species)
0 50 100 150 200 250 Time (millions of years ago)
© 2014 Pearson Education, Inc.
Regional Adaptive Radiations
Adaptive radiations can occur when organisms
colonize new environments with little competition
The Hawaiian Islands are one of the world’s great
showcases of adaptive radiation
© 2014 Pearson Education, Inc.
Figure 25.22
Dubautia waialealae
Dubautia laxa
Dubautia scabra Dubautia linearis
Argyroxiphium
sandwicense
HAWAII
MAUI LANAI
MOLOKAI
KAUAI
1.3
million years
0.4
million years
3.7
million years
OAHU
5.1
million years
Close North American relative, the tarweed Carlquistia muirii
© 2014 Pearson Education, Inc.
Figure 25.22a
HAWAII
MAUI LANAI
MOLOKAI
KAUAI
1.3
million
years
0.4
million
years
3.7
million
years
OAHU
5.1
million
years
© 2014 Pearson Education, Inc.
Figure 25.22b
Close North American
relative, the tarweed Carlquistia muirii
© 2014 Pearson Education, Inc.
Figure 25.22c
Dubautia waialealae
© 2014 Pearson Education, Inc.
Figure 25.22d
Dubautia laxa
© 2014 Pearson Education, Inc.
Figure 25.22e
Dubautia scabra
© 2014 Pearson Education, Inc.
Figure 25.22f
Argyroxiphium
sandwicense
© 2014 Pearson Education, Inc.
Figure 25.22g
Dubautia linearis
© 2014 Pearson Education, Inc.
Concept 25.5: Major changes in body form can result from changes in the sequences and regulation of developmental genes
Studying genetic mechanisms of change can
provide insight into large-scale evolutionary
change
© 2014 Pearson Education, Inc.
Effects of Developmental Genes
Genes that program development control the rate,
timing, and spatial pattern of changes in an
organism’s form as it develops into an adult
© 2014 Pearson Education, Inc.
Changes in Rate and Timing
Heterochrony is an evolutionary change in the
rate or timing of developmental events
It can have a significant impact on body shape
The contrasting shapes of human and chimpanzee
skulls are the result of small changes in relative
growth rates
© 2014 Pearson Education, Inc.
Figure 25.23
Chimpanzee infant
Chimpanzee fetus
Human fetus Human adult
Chimpanzee adult
Chimpanzee adult
© 2014 Pearson Education, Inc.
Figure 25.23a
Chimpanzee infant Chimpanzee adult
© 2014 Pearson Education, Inc.
Animation: Allometric Growth
© 2014 Pearson Education, Inc.
Heterochrony can alter the timing of reproductive
development relative to the development of
nonreproductive organs
In paedomorphosis, the rate of reproductive
development accelerates compared with somatic
development
The sexually mature species may retain body
features that were juvenile structures in an
ancestral species
© 2014 Pearson Education, Inc.
Figure 25.24
Gills
© 2014 Pearson Education, Inc.
Changes in Spatial Pattern
Substantial evolutionary change can also result
from alterations in genes that control the
placement and organization of body parts
Homeotic genes determine such basic features
as where wings and legs will develop on a bird or
how a flower’s parts are arranged
© 2014 Pearson Education, Inc.
Hox genes are a class of homeotic genes that
provide positional information during animal
embryonic development
If Hox genes are expressed in the wrong location,
body parts can be produced in the wrong location
For example, in crustaceans, a swimming
appendage can be produced instead of a feeding
appendage
© 2014 Pearson Education, Inc.
The Evolution of Development
The tremendous increase in diversity during the
Cambrian explosion is a puzzle
Developmental genes may play an especially
important role
Changes in developmental genes can result in
new morphological forms
© 2014 Pearson Education, Inc.
Changes in Genes
New morphological forms likely come from gene
duplication events that produce new
developmental genes
A possible mechanism for the evolution of six-
legged insects from a many-legged crustacean
ancestor has been demonstrated in lab
experiments
Specific changes in the Ubx gene have been
identified that can “turn off” leg development
© 2014 Pearson Education, Inc.
Figure 25.25
Hox gene 6 Hox gene 7 Hox gene 8
About 400 mya
Drosophila Artemia
Ubx
© 2014 Pearson Education, Inc.
Changes in Gene Regulation
Changes in morphology likely result from changes
in the regulation of developmental genes rather
than changes in the sequence of developmental
genes
For example, threespine sticklebacks in lakes have
fewer spines than their marine relatives
The gene sequence remains the same, but the
regulation of gene expression is different in the two
groups of fish
© 2014 Pearson Education, Inc.
Figure 25.26
Hypothesis A:
Hypothesis B:
Marine stickleback embryo: expression in ventral spine and mouth regions
Lake stickleback embryo: expression only in mouth regions
Result: Yes
Result: No The 283 amino acids of the Pitx1
protein are identical.
Differences in
sequence
Differences in
expression
Red arrows indicate regions of Pitx1
expression.
Results
© 2014 Pearson Education, Inc.
Figure 25.26a
Marine stickleback embryo: expression in ventral spine and mouth regions
Red arrows indicate regions of Pitx1
expression.
© 2014 Pearson Education, Inc.
Figure 25.26b
Lake stickleback embryo: expression only in mouth regions
Red arrows indicate regions of Pitx1
expression.
© 2014 Pearson Education, Inc.
Figure 25.26c
Threespine stickleback
(Gasterosteus aculeatus)
Ventral spines
© 2014 Pearson Education, Inc.
Concept 25.6: Evolution is not goal oriented
Evolution is like tinkering—it is a process in which
new forms arise by the slight modification of
existing forms
© 2014 Pearson Education, Inc.
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
© 2014 Pearson Education, Inc.
Figure 25.27
© 2014 Pearson Education, Inc.
Figure 25.28
(a) Patch of pigmented cells (b) Eyecup
(c) Pinhole camera-type eye (d) Eye with primitive lens (e) Complex camera lens-type eye
Pigmented cells
(photoreceptors)
Cornea
Lens
Retina
Optic
nerve
Example: Loligo, a squid
Optic nerve
Cornea Cellular
mass
(lens)
Example: Murex, a marine
snail Example: Nautilus
Optic
nerve
Epithelium
Example: Patella, a limpet
Epithelium
Pigmented
cells
Nerve fibers Nerve fibers
Example: Pleurotomaria,
a slit shell mollusc
Fluid-filled
cavity
Pigmented
layer
(retina)
© 2014 Pearson Education, Inc.
Figure 25.28a
(a) Patch of pigmented cells
Pigmented cells
(photoreceptors)
Example: Patella, a limpet
Nerve fibers
Epithelium
© 2014 Pearson Education, Inc.
Figure 25.28b
(b) Eyecup
Pigmented
cells
Nerve fibers
Example: Pleurotomaria,
a slit shell mollusc
© 2014 Pearson Education, Inc.
Figure 25.28c
(c) Pinhole camera-type eye
Example: Nautilus
Optic
nerve
Epithelium Fluid-filled
cavity
Pigmented layer (retina)
© 2014 Pearson Education, Inc.
Figure 25.28d
(d) Eye with primitive lens
Optic nerve
Cornea Cellular mass (lens)
Example: Murex, a marine
snail
© 2014 Pearson Education, Inc.
Figure 25.28e
(e) Complex camera lens-type eye
Cornea
Lens
Retina Optic
nerve
Example: Loligo, a squid
© 2014 Pearson Education, Inc.
Evolutionary Trends
Extracting a single evolutionary progression from
the fossil record can be misleading
Apparent trends should be examined in a broader
context
The species selection model suggests that
differential speciation success may determine
evolutionary trends
Evolutionary trends do not imply an intrinsic drive
toward a particular phenotype
© 2014 Pearson Education, Inc.
Figure 25.29
Holocene
Pliocene
Pleistocene 0
5
10
15
20
25
30
35
40
45
50
55
Eo
ce
ne
O
lig
oc
en
e
Mio
ce
ne
Anchitherium
Sin
oh
ipp
us
Me
gah
ipp
us
Hyp
oh
ipp
us
Arc
ha
eo
hip
pu
s
Pa
rah
ipp
us
Pliohippus
Merychippus
Hip
pari
on
Neo
hip
pa
rio
n
Nan
nip
pu
s
Hip
pid
ion
an
d
clo
se
re
lati
ve
s
Call
ipp
us
Mesohippus
Ep
ihip
pu
s
Mio
hip
pu
s
Hap
loh
ipp
us
Pa
lae
oth
eri
um
Pa
ch
yn
olo
ph
us
Pro
pa
lae
oth
eri
um
Oro
hip
pu
s
Hyracotherium
relatives Hyracotherium
Grazers Browsers
Mil
lio
ns
of
ye
ars
ag
o
Equus
© 2014 Pearson Education, Inc.
Figure 25.29a
Grazers Browsers
30
35
40
45
50
55
Eo
cen
e
Mesohippus
Ep
ihip
pu
s
Hap
loh
ipp
us
Pala
eo
theri
um
Pach
yn
olo
ph
us
Pro
pala
eo
theri
um
Oro
hip
pu
s
Hyracotherium relatives
Hyracotherium
Oli
go
cen
e
Mil
lio
ns o
f years
ag
o
Mio
hip
pu
s 25
© 2014 Pearson Education, Inc.
Figure 25.29b
Grazers Browsers
Pliohippus
Merychippus
Hip
pari
on
Neo
hip
pari
on
Anchitherium
Sin
oh
ipp
us
Meg
ah
ipp
us
Hyp
oh
ipp
us
Arc
haeo
hip
pu
s
Para
hip
pu
s
Equus
Mio
-
hip
pu
s
Mio
cen
e
Pliocene
Pleistocene
Holocene 0
5
10
15
20
25
Mil
lio
ns o
f years
ag
o
© 2014 Pearson Education, Inc.
Figure 25.UN07a
Species with planktonic larvae
65
Species with
nonplanktonic
larvae
60 55 50 45 40 35
Millions of years ago (mya)
Paleocene Eocene
© 2014 Pearson Education, Inc.
Figure 25.UN07b
© 2014 Pearson Education, Inc.
Figure 25.UN08
3.5 billion years
ago (bya):
First prokaryotes (single-celled)
1.8 bya:
First eukaryotes
(single-celled)
1.2 bya:
First
multicellular eukaryotes
500 mya:
Colonization
of land by fungi, plants,
and animals
535–525 mya:
Cambrian explosion
(great increase in diversity of animal forms)
Millions of years ago (mya)
4,000 3,500 3,000 2,500 2,000 1,500 1,000 500
Pre
sen
t
© 2014 Pearson Education, Inc.
Figure 25.UN09
Flies and fleas
Moths and butterflies
Caddisflies
Herbivory
© 2014 Pearson Education, Inc.
Figure 25.UN10
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