Transcript common ancestor

Chapter 19: pp. 337 - 353
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10th Edition
Sylvia S. Mader
Systematics &
Phylogeny
BIOLOGY
(All): © Sylvia S. Mader
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
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Outline
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Taxonomy
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Binomial System
Species Identification
Classification Categories
Phylogenetic Trees
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Systematics
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Systematics Today
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Taxonomy (naming of organisms)
Classification (placing species in the proper categories)
Cladistic Systematics
Phenetic Systematics
Classification Systems
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The Five Kingdom System
The Three Domain System
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Taxonomy
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Taxonomy is the branch of biology concerned
with identifying, naming, and classifying
organisms.
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A natural system of classification reflects the
evolutionary history of organisms.
Naming and identifying organisms began with the
Greeks and Romans.
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Aristotle classified organisms into groups such as horses,
birds, and oaks
In the Middle Ages, organisms were described using
long Latin descriptions.
John Ray (1627-1705),
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Argued that each organism should have a set name.
Otherwise, “men…cannot see and record accurately.”
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Taxonomy: Binomial System
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Mid-eighteenth century, Linnaeus
developed the binomial system of
nomenclature
First word is genus name
 Second word is specific epithet
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Refers to one species (of potentially many) within its
genus
A species is referred to by the full binomial
name (Genus species)
 Genus name can be used alone to refer to a
group of related species
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Taxonomy: Distinguishing Species
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Distinguishing species on the basis of
structure can be difficult
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Members of the same species can vary in
structure
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Attempts to demonstrate reproductive isolation
is problematic because:
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Some species hybridize, and
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Reproductive isolation is difficult to observe
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Classification Categories
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Aristotle classified life into 14 groups (e.g., mammals,
birds, etc.),
Ray grouped animals and plants according to how he
thought they were related.
Modern taxonomists use the following classification:
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Species
Genus – one or more species
Family – one or more genera
Order – one or more families
Class – one or more orders
Phylum – one or more classes
Kingdom – one or more phyla
Domain – one or more kingdoms
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Hierarchy of Taxa for
Parthenocissus quinquefolia
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DOMAINS
KINGDOMS
PHYLA
CLASSES
ORDERS
Eukarya
FAMILIES
Plantae
Anthophyta
GENERA
Eudicotyledones
Vitales
Vitaceae
SPECIES
Parthenocissus
P. quinquefolia
Parthenocissus quinquefolia
Virginia creeper (five-leaf ivy)
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Classification Categories
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The higher the category, the more inclusive
Organisms in the same domain have general
characteristics in common
Members of a species share quite specific characters.
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A character is any structural, chromosomal, or molecular feature
that distinguishes one group from another
In most cases, classification categories can be subdivided
into additional categories
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Superorder
Order
Suborder
Infraorder
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Phylogenetic Trees
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Systematics is the study of diversity of organisms using
information from cellular to population levels
One goal of systematics is to determine phylogeny
(evolutionary history) of a group
Phylogeny is the evolutionary history of a group of
organisms.
Phylogeny often represented as a phylogenetic tree
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A diagram indicating lines of descent
Each branching point:
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Is a divergence from a common ancestor
Represents an organism that gives rise to two new groups
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Classification and Phylogeny
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monkeys
apes
common
ancestor
(mobile limbs)
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reindeer
monkeys
apes
common ancestor
(placental mammal)
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Classification and Phylogeny
Order
Family
Genus
Species
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Aepycero
s
Melampus
(impala)
Oryx
gazella
(oryx)
Cervus
elaphus
(red deer)
Rangifer
tarandus
(reindeer)
Aepyceros
Oryx
Cervus
Rangifer
Bovidae
Cervidae
Artiodactyla
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Phylogenetic Trees
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Classification lists the unique characters of
each taxon and is intended to reflect
phylogeny
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Primitive characters:
Present in all members of a group, and
 Present in the common ancestor
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Derived characters:
Present in some members of a group, but
 Absent in the common ancestor
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Cladistic Systematics
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Cladistics analyze primitive and derived characters and
constructs cladograms on the basis of shared derived
characters.
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Arrange taxa into a cladogram
A cladogram is a special type of phylogenetic tree
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A clade is an evolutionary branch that includes:
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A common ancestor, together with
All its descendent species
It traces the evolutionary history of the group being studied.
Constructing a Cladogram
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First step: construct a table of characters of the taxa being
compared.
Any character found in the outgroup as well is a shared primitive
character.
Homologies shared by certain lineages are shared derived
characters.
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Constructing a Cladogram:
Phylogenetic Tree
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enlarged brain
common ancestor
hair, mammary glands
Amniotic
egg
chimpanzee
long canine teeth
terrier
feathers
gizzard
four limbs
finch
crocodile
epidermal
scales
lizard
vertebrae
frog
common
ancestor
tuna
lancelet (outgroup)
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Parsimony
Cladists are guided by the principle of
parsimony—the minimum number of
assumptions is most logical.
 The best cladogram is one in which the
fewest number of shared derived
characters are left unexplained or that
minimizes the number of assumed
evolutionary changes.
 Reliability of cladograms is dependent on
the knowledge and skill of a investigator.
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Different Grouping of Species
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D
D
B
B
C
A
E
F
G
common ancestor
D
H
I
Monophyletic grouping: This group is a clade
because it contains B, closest common
ancestor, and all the descendants of B.
B
C
A
E
F
G
H
C
A
F
G
I
Paraphyletic grouping: This group is not a clade
because it lacks F, also a descendant of the
common ancestor B.
E
H
I
Polyphyletic grouping: This group is not a
clade because it lacks A, the closest
common ancestor to all the descendants.
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Terms Used in Cladistics
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Tracing Phylogeny
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Fossil Record
Fossil record is incomplete
 It is often difficult to determine the phylogeny of
a fossil
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Homology
Refers to features that stem from a common
ancestor
 Homologous structures are related to each
other through common descent
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Analogy
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Similarity due to convergence
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Ancestral Angiosperm
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fruits
paired
stamens
© David Dilcher and Ge Sun
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Tracing Phylogeny
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Convergent Evolution
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The acquisition of a feature in distantly related lines of
descent
The feature is not present in a common ancestor
Similar structures are due to adaptation to the same
type environment
Parallel Evolution
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The acquisition of a feature in two or more related
lineages
The feature is not present in a common ancestor
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Molecular Data
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Protein Comparisons
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Immunological techniques
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Amino acid sequencing
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Similar sequence in same protein indicates close relationship
RNA and DNA Comparisons
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Systematics assumes:
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Degree of cross reaction used to judge relationship
Two species with similar base-pair sequences are assumed to
be closely related
Two species with differing base-pair sequences are assumed
to be only distantly related
Molecular Clocks
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Use non adaptive nucleotide sequences
Assumed constant rate of mutation over time
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Molecular Data
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human
common
chimpanzee
white-handed
gibbon
rhesus
monkey
green
monkey
capuchin
monkey
60
50
40
30
20
10
Million years ago (MYA)
PRESENT
Increased difference in DNA
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Three-Domain System
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Sequencing of rRNA suggests all organisms
evolved along three distinct lineages:
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Domain Bacteria
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Prokaryotic unicellular organisms that reproduce asexually.
Cyanobacteria are large photosynthetic prokaryotes.
Most bacteria are heterotrophic.
Important in ecosystems - keeping chemical cycling going.
Some bacteria are parasitic and cause disease.
Domain Archaea
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Prokaryotic unicellular organisms that reproduce asexually.
Live in extreme environments
Cell wall is diverse but not the same as the bacterial cell wall.
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Three-Domain System
Domain Eukarya
 Unicellular and multicellular organisms
 Cells with a membrane-bounded nucleus
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Sexual reproduction common
 Contains four kingdoms
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Kingdom Protista
Kingdom Fungi
Kingdom Plantae
Kingdom Animalia
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Tree of Life Showing The Three Domains
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fungi
animals
plants
EUKARYA
protists
protists
heterotrophic
bacteria
cyanobacteria
BACTERIA
ARCHAEA
common ancestor
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Major Difference of Three Domains
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