Download Taxonomy Five Kingdoms Three Domains Evolutionary Trees

Taxonomy
Five Kingdoms
R.H Whittaker
1969
Three Domains
Evolutionary Trees
Cladistics:
Cladograms and
molecular data
What are the tools used by scientists
to observe and understand
evolutionary relationships?
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Artificial Selection
1. Artificial selection
2. Fossil record
3. Comparative anatomy
4. Comparative embryology
5. Comparative biochemistry
6. Biogeography
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The fossil record: A gallery of fossils
What about analogous
structures?
• Convergent evolution
• Co-evolution
Molecular Data and the Evolutionary Relationships of
Vertebrates
Homologous structures: anatomical signs of descent with
modification
Comparative Embryology:
• “Ontogeny recapitulates
phylogeny” - the
appearance of ancestral
structures in the embryos
of modern descendants
(Haeckel)
Biogeography - Wallace’s line
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Some major episodes in the history of life
Evidence from biogeographical
studies:
Figure 25.8 Taxonomy starts with the latin binomial, and exhibits a hierarchical
structure reflecting phylogenetic relationships among taxa or groups of organisms
Systematics: connecting phylogeny
and taxonomy
Latin “binomial” or
two-part name
(genus and species)
• Taxonomy = the science of classifying
organisms
• Phylogenetics = the study of phylogeny, or the
history of evolutionary relationships among
species
Figure 25.9 The connection between classification and phylogeny: this phylogenetic tree
organizes taxa into a hypothesized tree of evolutionary relatedness, with species at the
tips of the branches.
Perceived similarities can be misleading
How are these
phylogenetic
trees
constructed?
Traditional Approach:
Phenetics
Classifications based
on perceived overall
similarity
Jellyfish
Starfish
Human
Which pair is most similar?
Which pair is most closely related?
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Perceived similarities can be misleading
Jellyfish
Starfish
• Live in water
• No backbone
Human
Perceived similarities can be misleading
Jellyfish
Starfish
Human
• Live on land
• Have backbone
Classification based on phylogeny
• Phylogeny = patterns of ancestry
• Cladistics introduced by Willi Hennig in
1950’s
Classification based on phylogeny
• Phylogeny = patterns of ancestry
• Cladistics introduced by Willi Hennig in
1950’s
• Goals of cladistics:
– Base classifications on phylogeny
– Recognize continuum of evolution
– Make taxonomists “show their work”, make
explicit hypotheses based on data they
present
Key principles of cladistics
• Since organisms are related by descent, close
relationship implies recent common ancestors.
• Organisms differ genetically and pass on these
differences (and resultant traits) to their ancestors.
• Therefore, organisms which are closely related
should share new features, acquired by evolution,
that are not present in other groups.
• These uniquely shared derived characters are the
best guide to the evolutionary sequence.
The more DERIVED characters
two lineages share, the more
closely related they are.
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Derived characters are identified
through comparison with an
outgroup.
• An outgroup is a taxon known (or
assumed) to have diverged from a
common ancestor less recently than
any of the other taxa we wish to
classify
– Relies on other studies, theory, or
intuition
Adding an outgroup to our comparison
Sponge
Jellyfish
Starfish
Human
Derived characters are identified
through comparison with an
outgroup.
• An outgroup is a taxon known (or
assumed) to have diverged from a
common ancestor less recently than any of
the other taxa we wish to classify
• Then derived characters are those which
are found in some of the taxa under
consideration but not the outgroup.
Derived characters must be absent
from outgroup
Sponges, jellyfish, and starfish all live in water
and do not have backbones, therefore these are
NOT derived characters.
Derived characters found in only one
taxon set it apart
Sponge
Jellyfish
Starfish
Human
Backbones and living on land are unique to
humans.
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Derived characters found in only one
taxon set it apart
Sponge
Jellyfish
Starfish
Human
backbone
Derived characters found in all taxa do
not resolve relationships
Sponge
Jellyfish
Starfish
Derived characters found in all taxa do
not resolve relationships
Human
Sponges have only one tissue layer.
The other taxa all have multiple tissue layers.
Shared, derived characters group
related taxa together
Sponges and jellyfish lack enclosed body cavities.
(ancestral)
Starfish and humans have enclosed body cavities.
(derived)
multiple tissue layers
Shared, derived characters group
related taxa together
Sponges and jellyfish lack enclosed body cavities.
(ancestral)
Starfish and humans have enclosed body cavities.
(derived)
Shared derived characters are called SYNAPOMORPHIES.
Shared, derived characters group
related taxa together
Sponge
Jellyfish
Starfish
Human
enclosed body cavities
multiple tissue layers
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We have just made a cladogram
• Phylogenetic tree showing the order
in which different lineages diverged
from a common ancestor
We have just made a cladogram
• Phylogenetic tree showing the order
in which different lineages diverged
from a common ancestor
• Each branch point is labeled with (a)
diagnostic synapomorphy(ies)
– This is what allows others to “check our
work”
We have just made a cladogram
• Phylogenetic tree showing the order in
which different lineages diverged from a
common ancestor
• Each branch point is labeled with (a)
diagnostic synapomorphy(ies)
• Each synapomorphy is found on one
branch of the tree but not the other
branch
Synapomorphies mark each branch on
a cladogram
Sponge
Jellyfish
Starfish
Human
enclosed body cavities
multiple tissue layers
Figure 25.10 Note: Legitimate taxa, such as genera or families, are composed of
monophyletic groups of species. These represent evolutionarily unified groups.
What are shared, derived,
homologous traits?
•Monophyletic groups contain a common ancestor and all of its descendants.
•Paraphyletic groups are missing one or more descendants, and polyphyletic
groupings are missing a common ancestor.
• Shared traits are similarities among organisms
• Some similarities are homologous, i.e. shared
because of inheritance from a common
ancestor
• Other similarities are analogous, i.e. due to
convergent evolution, NOT from inheritance
from a common ancestor
•How do we construct hypothesized monophyletic groups? Using shared,
derived, homologous traits.
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Algae
Fern
Pine
Cherry
Algae
Fern
Pine
Flowers
Cherry
Flowers
Woody Stem
Woody Stem
Lives on land
Lives on land
Ancestral trait shared by all 4 taxa
Photsoynthesizes
Algae
Fern
Photsoynthesizes
Pine
Cherry
Algae
Fern
Pine
Cherry
Loss of “broad leaves”
“broad leaves”
“broad leaves”
Flowers
Flowers
Woody Stem
Woody Stem
“broad leaves”
Lives on land
salamander
hawk
wings
Lives on land
squirrel
wings
bat
What it means if a taxa has an
ancestral trait
• For the character under question, the state of
the character matches the character state in
the outgroup
• E.g., ferns display the ancestral trait for the
character state: does it have woody stem
• This does not mean that the fern is the
ancestor to any of the other taxa
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