Transcript Ch25 7th Ed

Phylogeny
The evolutionary history of a
species or group of species
Based on common ancestries
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Fossil Record
– Provides information about ancient organisms
Figure 25.1
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Systematics
– As an analytical approach to understanding the
diversity and relationships of organisms, both
present-day and extinct
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• Currently, systematists use
– Morphological, biochemical, and molecular
comparisons to infer evolutionary relationships
Figure 25.2
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The Fossil Record
• Sedimentary rocks
– Are the richest source of fossils
– Are deposited into layers called strata
1 Rivers carry sediment to the
ocean. Sedimentary rock layers
containing fossils form on the
ocean floor.
2 Over time, new strata are
deposited, containing fossils
from each time period.
3 As sea levels change and the seafloor
is pushed upward, sedimentary rocks are
exposed. Erosion reveals strata and fossils.
Younger stratum
with more recent
fossils
Figure 25.3
Older stratum
with older fossils
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• Though sedimentary fossils are the most
common
– Paleontologists study a wide variety of fossils
(c) Leaf fossil, about 40 million years old
(b) Petrified tree in Arizona, about
190 million years old
(a) Dinosaur bones being excavated
from sandstone
(d) Casts of ammonites,
about 375 million
years old
(f) Insects
preserved
whole in
amber
Figure 25.4a–g
(g) Tusks of a 23,000-year-old mammoth,
frozen whole in Siberian ice
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(e) Boy standing in a 150-million-year-old
dinosaur track in Colorado
• Convergent evolution occurs when similar
environmental pressures and natural selection
– Produce similar (analogous) adaptations in
organisms from different evolutionary lineages
Figure 25.5
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Hierarchical Classification
• Linnaeus also introduced a system
– For grouping species in increasingly broad
categories
Panthera
Species pardus
Panthera
Genus
Felidae
Family
Carnivora
Order
Class
Phylum
Kingdom
Figure 25.8
Domain
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Mammalia
Chordata
Animalia
Eukarya
Linking Classification and Phylogeny
• Systematists depict evolutionary relationships
Species
Panthera
Order
Family
Panthera
Mephitis
Canis
Canis
Lutra lutra
pardus
mephitis
familiaris
lupus
(European
(leopard) (striped skunk)
(domestic dog) (wolf)
otter)
Genus
– In branching phylogenetic trees
Mephitis
Felidae
Lutra
Mustelidae
Carnivora
Figure 25.9
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Canis
Canidae
• Each branch point
– Represents the divergence of two species
Leopard
Domestic cat
Common ancestor
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• “Deeper” branch points
– Represent progressively greater amounts of
divergence
Wolf
Leopard
Common ancestor
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Domestic cat
• The outgroup comparison
– Enables us to focus on just those characters
that were derived at the various branch points
in the evolution of a clade
Lamprey
Tuna
Salamander
Turtle
Leopard
Hair
0
0
0
0
0
1
Amniotic (shelled) egg
0
0
0
0
1
1
Four walking legs
0
0
0
1
1
1
Hinged jaws
0
0
1
1
1
1
Vertebral column (backbone)
0
1
1
1
1
1
CHARACTERS
Lancelet
(outgroup)
TAXA
Turtle
Salamander
(a) Character table. A 0 indicates that a character is absent; a 1
indicates that a character is present.
Leopard
Hair
Amniotic egg
Tuna
Lamprey
Four walking legs
Hinged jaws
Lancelet (outgroup)
Figure 25.11a, b
Vertebral column
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(b) Cladogram. Analyzing the distribution of these
derived characters can provide insight into vertebrate
phylogeny.
Phylogenetic Trees as Hypotheses
• The best hypotheses for phylogenetic trees
– Are those that fit the most data: morphological,
molecular, and fossil
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• Sometimes there is compelling evidence
– That the best hypothesis is not the most
parsimonious
Bird
Lizard
Mammal
Four-chambered
heart
(a) Mammal-bird clade
Bird
Lizard
Mammal
Four-chambered
heart
Four-chambered
heart
Figure 25.16a, b
(b) Lizard-bird clade
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• Much of an organism’s evolutionary history is
documented in its genome
• Comparing nucleic acids or other molecules to
infer relatedness
– Is a valuable tool for tracing organisms’
evolutionary history
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Gene Duplications and Gene Families
• Gene duplication
– Is one of the most important types of mutation
in evolution because it increases the number
of genes in the genome, providing further
opportunities for evolutionary changes
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• Orthologous genes
– Are genes found in a single copy in the
genome
– Can diverge only once speciation has taken
place
Ancestral gene
Speciation
(a)
Orthologous genes
Figure 25.17a
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• Paralogous genes
– Result from gene duplication, so they are
found in more than one copy in the genome
– Can diverge within the clade that carries them,
often adding new functions
Ancestral gene
Gene duplication
Figure 25.17b
(b)
Paralogous genes
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Molecular Clocks
• The molecular clock
– Is a yardstick for measuring the absolute time
of evolutionary change based on the
observation that some regions of genomes
appear to evolve at relatively constant rates
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Applying a Molecular Clock: The Origin of HIV
• Phylogenetic analysis shows that HIV
– Is descended from viruses that infect
chimpanzees and other primates
• A comparison of HIV samples from throughout
the epidemic
– Has shown that the virus has evolved in a
remarkably clocklike fashion
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The Universal Tree of Life
•
The tree of life
–
•
Is divided into three great clades called domains: Bacteria,
Archaea, and Eukarya
The early history of these domains is not yet clear
Billion years ago
Bacteria
Eukarya Archaea
0
4
Symbiosis of
chloroplast
ancestor with
ancestor of green
plants
1
3
Symbiosis of
mitochondrial
ancestor with
ancestor of
eukaryotes
2
Possible fusion
of bacterium
and archaean,
yielding
ancestor of
eukaryotic cells
1
Last common
ancestor of all
living things
4
2
3
2
3
1
Origin of life
Figure 25.18
4
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