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Chapter 25 and 26
•
Past organisms were very different from those now alive
•
macroevolutionary
The fossil record shows ______________________
changes over large time
scales including
–
terrestrial
The emergence of ________________
vertebrates
–
photosynthesis
The origin of __________________
–
mass extinctions
Long-term impacts of _________
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:
Abiotic
1. _______________
synthesis of small organic molecules
macromolecules
2. Joining of these small molecules into _____________________
“protobionts”
3. Packaging of molecules into _____________________
self-replicating
4. Origin of ________________________
molecules
Synthesis of Organic Compounds on Early Earth
•
Earth formed about 4.6 billion years ago, along with the rest of the solar
system
•
Earth’s early atmosphere likely contained water vapor and chemicals released
by volcanic eruptions (nitrogen, nitrogen oxides, carbon dioxide, methane,
ammonia, hydrogen, hydrogen sulfide)
•
A. I. Oparin and J. B. S. Haldane hypothesized that the early atmosphere was
a reducing environment
•
Stanley Miller and Harold Urey conducted lab experiments that showed that
abiotic synthesis
the ______________________
of organic molecules in a reducing
atmosphere is possible
Protobionts
•
Replication
metabolism
_____________
and ___________________
are key properties of life
•
Protobionts
________________
are aggregates of abiotically produced molecules
surrounded by a membrane or membrane-like structure
•
Protobionts exhibit simple reproduction and metabolism and maintain an
internal chemical environment
Self-Replicating RNA and the Dawn of Natural Selection
•
RNA
The first genetic material was probably ________,
not DNA
•
ribozymes
RNA molecules called ____________
have been found to catalyze many
different reactions
–
For example, ribozymes can make complementary copies of short stretches of
their own sequence or other short pieces of RNA
•
self-replicating
catalytic RNA
Early protobionts with ____________________,
___________________
would have been more effective at using resources and would have increased in
number through natural selection
•
The early genetic material might have formed an “RNA world”
1/
Remaining
“parent”
isotope
1
2
Accumulating
“daughter”
isotope
1/
2
4
Time (half-lives)
1/
3
8
1/
16
4
Radiocarbon dating can be used to date fossils up to 75,000 years old
For older fossils, some isotopes can be used to date sedimentary rock
layers above and below the fossil
Fig. 25-4
Present
Rhomaleosaurus victor,
a plesiosaur
Dimetrodon
Casts of
ammonites
Hallucigenia
Coccosteus cuspidatus
Dickinsonia
costata
Stromatolites
Tappania, a
unicellular
eukaryote
Fossilized
stromatolite
Humans
Colonization
of land
Animals
Origin of solar
system and
Earth
4
1
Proterozoic
2
Archaean
3
Multicellular
eukaryotes
Single-celled
eukaryotes
Atmospheric
oxygen
Prokaryotes
Photosynthesis and the Oxygen Revolution
•
Most atmospheric oxygen (O2) is of biological origin
•
cyanobacteria
The source of O2 was likely bacteria similar to modern _________________
•
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 2.2 billion years ago
– Posed a challenge for life
– Provided opportunity to gain energy from light
– Allowed organisms to exploit new ecosystems
The First Eukaryotes
•
The oldest fossils of eukaryotic cells date back 2.1 billion years
•
endosymbiosis
The hypothesis of ________________
proposes that mitochondria and
plastids (chloroplasts and related organelles) were formerly small prokaryotes
living within larger host cells
•
The prokaryotic ancestors of mitochondria and plastids probably gained entry
undigested prey
internal parasites
to the host cell as __________________
or ________________________
•
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
•
Key evidence supporting an endosymbiotic origin of mitochondria and plastids:
–
inner membrane
Similarities in ____________________
structures and functions
–
Division
_____________
is similar in these organelles and some prokaryotes
–
own DNA
These organelles transcribe and translate their _____________
–
ribosomes
Their _________________
are more similar to prokaryotic than eukaryotic
ribosomes
Plasma membrane
Cytoplasm
Ancestral
prokaryote
DNA
Endoplasmic reticulum
Nuclear envelope
Nucleus
Plasma membrane
Cytoplasm
Ancestral
prokaryote
DNA
Endoplasmic reticulum
Nucleus
Nuclear envelope
Aerobic
heterotrophic
prokaryote
Photosynthetic
prokaryote
Mitochondrion
Ancestral
heterotrophic
eukaryote
Mitochondrion
Plastid
Ancestral photosynthetic
eukaryote
The Origin of Multicellularity
•
The evolution of eukaryotic cells allowed for a greater range of unicellular
forms
•
multicellularity
A second wave of diversification occurred when _________________
evolved
and gave rise to algae, plants, fungi, and animals
Adaptive Radiations
•
Adaptive radiation is the evolution of diversely adapted species from a
common ancestor
_______________________
upon introduction to new environmental
opportunities
•
allopatric speciation
The break-up of Pangaea lead to ______________________
•
The current distribution of fossils reflects the movement of continental drift
•
For example, the similarity of fossils in parts of South America and Africa is
consistent with the idea that these continents were formerly attached
Worldwide Adaptive Radiations
•
Mammals underwent an adaptive radiation after the extinction of
dinosaurs
________________
•
The disappearance of dinosaurs (except birds) allowed for the expansion of
mammals in diversity and size
•
photosynthetic prokaryotes large
Other notable radiations include ________________________,
land plants insects, and tetrapods
predators in the Cambrian, ___________,
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
Cenozoic
Present
Eurasia
Africa
65.5
South
America
India
Madagascar
251
Mesozoic
135
Paleozoic
Millions of years ago
Antarctica
800
700
15
600
500
10
400
300
5
200
100
0
Era
Period
542
E
O
Paleozoic
S
D
488 444 416
359
C
Tr
P
299
251
Mesozoic
C
J
200
145
Time (millions of years ago)
Cenozoic
P
65.5
N
0
0
Number of families:
Total extinction rate
(families per million years):
20
Changes in Rate and Timing
•
•
Newborn
2
5
Age (years)
15
Adult
(a) Differential growth rates in a human
Chimpanzee fetus
Chimpanzee adult
Human fetus
Human adult
(b) Comparison of chimpanzee and human skull growth
•
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
•
•
•
reproductive
Heterochrony can alter the timing of _______________
development relative
to the development of nonreproductive organs
paedomorphosis
In ________________,
the rate of reproductive development accelerates
compared with somatic development
The sexually mature species may retain body features that were juvenile
ancestral species
structures in an __________________
Gills
1.2 bya:
First multicellular eukaryotes
2.1 bya:
First eukaryotes (single-celled)
535–525 mya:
Cambrian explosion
(great increase
in diversity of
animal forms)
3.5 billion years ago (bya):
First prokaryotes (single-celled)
Millions of years ago (mya)
500 mya:
Colonization
of land by
fungi, plants
and animals
Origin of solar system
and Earth
4
1
Proterozoic
2
Archaean
3
Investigating the Tree of Life
•
history
Phylogeny is the evolutionary ___________
of a species or group of related
species
•
The discipline of systematics classifies organisms and determines their
relationships
evolutionary _________________
•
Systematists use fossil, molecular, and genetic data to infer evolutionary
relationships
•
division and ____________
naming
Taxonomy is the ordered __________
of organisms
•
taxon
A taxonomic unit at any level of hierarchy is called a _____________
•
Systematists depict evolutionary relationships in branching
phylogenetic trees
____________________________
•
A phylogenetic tree represents a hypothesis about evolutionary relationships
•
Each branch point represents the divergence of two species
•
common
Sister taxa are groups that share an immediate ___________
ancestor
taxons
Order
Family Genus
Species
Taxidea
Taxidea
taxus
Lutra
Mustelidae
Panthera
Felidae
Carnivora
Panthera
pardus
Lutra lutra
Canis
Canidae
Canis
latrans
Canis
lupus
The connection
between
classification and
phylogeny
Sorting Homology from Analogy
•
When constructing a phylogeny, systematists need to distinguish whether a
homology
analogy
similarity is the result of _____________
or _____________
•
shared ancestry
Homology is similarity due to ____________________
•
convergent
Analogy is similarity due to __________________
evolution
Cladistics
•
common descent
Cladistics groups organisms by ____________________
•
A clade is a group of species that includes an ancestral species and all its
descendants
•
Clades can be nested in larger clades, but not all groupings of organisms qualify
as clades
Cladogram - a tree constructed from a
series of
dichotomies or two-way branch points
A valid clade ismonophyletic
_______________, signifying that it consists of the
ancestor species and all its descendants
paraphyletic
A _______________
grouping consists of an ancestral species and some, but not all,
of the descendants
polyphyletic
A _______________
grouping consists of various species that lack a common ancestor
A
A
A
B
B
C
C
C
D
D
D
E
E
F
F
F
G
G
G
B
Group I
(a) Monophyletic group (clade)
Group II
(b) Paraphyletic group
E
Group III
(c) Polyphyletic group
Shared Ancestral and Shared Derived Characters
•
In comparison with its ancestor, an organism has both shared and derived
characteristics
•
shared ancestral character
A ______________________________
is a character that originated in an
ancestor of the taxon
•
shared derived character
A ______________________________
is an evolutionary novelty unique to
a particular clade
•
A character can be both ancestral and derived, depending on the context
Inferring Phylogenies Using Derived Characters
•
When inferring evolutionary relationships, it is useful to know in which clade a
shared derived character first appeared
Constructing a phylogenetic tree
An outgroup is a species or group of species that is closely related to
the ingroup, the various species being studied
Systematists compare each ingroup species with the outgroup to
differentiate between shared derived and shared ancestral
characteristics
TAXA
Lancelet
Tuna
Leopard
(outgroup)
Vertebral column
(backbone)
0
1
1
1
1
1
Hinged jaws
0
0
1
1
1
1
Lamprey
Tuna
Vertebral
column
Salamander
Hinged jaws
Four walking legs
0
0
0
1
1
1
Turtle
Four walking legs
Amniotic (shelled) egg
0
0
0
0
1
1
Hair
0
0
0
0
0
1
Amniotic egg
(a) Character table
Leopard
Hair
(b) Phylogenetic tree
•
Maximum parsimony
______________________
assumes that the tree that requires the fewest
evolutionary events (appearances of shared derived characters) is the most
likely
•
The principle of maximum likelihood states that, 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
Human
Mushroom
Tulip
0
30%
40%
0
40%
Human
Mushroom
0
Tulip
(a) Percentage differences between sequences
15%
5%
5%
15%
15%
10%
20%
25%
Tree 1: More likely
Tree 2: Less likely
(b) Comparison of possible trees
Species I
Species III
Species II
Three phylogenetic hypotheses:
I
I
III
II
III
II
III
II
I
From Two Kingdoms to Three Domains
•
Early taxonomists classified all species as either plants or animals
•
Later, five kingdoms were recognized: Monera (prokaryotes), Protista, Plantae,
Fungi, and Animalia
•
More recently, the three-domain system has been adopted: Bacteria, Archaea,
and Eukarya
•
The three-domain system is supported by data from many sequenced genomes
A Simple Tree of All Life
•
eukaryotes
archaea
The tree of life suggests that _______________
and ____________
are
bacteria
more closely related to each other than to __________________
•
The tree of life is based largely on rRNA genes, as these have evolved slowly
•
interchanges
There have been substantial ___________________
of genes between
organisms in different domains
•
Horizontal gene transfer is the movement of genes from one genome
_________________________
to another
•
Horizontal gene transfer complicates efforts to build a tree of life
EUKARYA
Dinoflagellates
Forams
Ciliates Diatoms
Red algae
Land plants
Green algae
Cellular slime molds
Amoebas
Euglena
Trypanosomes
Leishmania
Animals
Fungi
Sulfolobus
Green nonsulfur bacteria
Thermophiles
Halophiles
(Mitochondrion)
COMMON
ANCESTOR
OF ALL
LIFE
Methanobacterium
ARCHAEA
Spirochetes
Chlamydia
Green
sulfur bacteria
BACTERIA
Cyanobacteria
(Plastids, including
chloroplasts)