Transcript not evolutionary relationships

Fields of Study in Animal Diversity
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Phylogeny
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Systematics
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Determining evolutionary relationships of
organisms (the study of phylogeny).
Taxonomy
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The evolutionary history of a species or group of
related species.
Assigning organisms to different categories
based on their evolutionary relationships.
Nomenclature
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The science of naming organisms
The Kingdoms
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How are relationships – evolutionary relationships – determined?
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Structure
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Breeding behavior
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Geographical distribution
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Chromosome comparison
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Biochemistry
These provide clues to how organism evolved
Structure
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Many shared physical traits implies species are closely related
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Came from a common ancestor:
Examples
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Lynx and bobcats have similar structure (skeletal) = more
similarities than to any other groups
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Dandelions and sunflowers = similar flower and fruit
structures
Conclusion
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So what happens if you come across an unknown animal that can retract its
claws similar to:
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Lions
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Tigers
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Bobcats
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Lynxes?
What family should it belong to?
Breeding Behavior
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What if two species live in the same area, and are similar in structure?
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What else could you do analyze to determine if one species, or two different?
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Look at breeding patterns
Example
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2 species of frog:
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Hyla versicolor
–
Hyla chrysoscelis
During mating season, the males make different sounds to attract females,
only mate with females of their own species
Geographical distribution
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Location of species on Earth helps biologists determine relationships with
other species
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Similarities between species separated by large distances show common
ancestry
Example
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Many species of finches on the Galapagos Islands off the coast of South
America
Example
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How did the birds get there?
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Some members of species of finches from South America reached the
Galapagos Islands
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These finches spread into different habitats and evolved into diverse
species…but kept genetic similarities
Chromosome Comparison
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Number and structure of chromosomes
Example
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The following all look different, grow in separate climates, however they all
have nearly identical chromosomal structure!!
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Cauliflower
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Cabbage
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Kale
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Broccoli
Example
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Humans, gorillas and chimpanzees have chromosomes with similar appearances
Chromosomal Comparisons
Chromosomes of Unrelated Species
Bacteria
Other Species
Conclusion
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Chromosomal similarities suggest a common ancestry
Biochemistry
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Biochemical – DNA – evidence shows closely related species have similar DNA
sequences
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Similar proteins
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Each specie’s DNA has a unique sequence and order:
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DNA
is located on a small section of
the chromosome
Example
≠
║
║
Conclusion
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The more similarities two species have between the sequence/order of their
DNA molecule, the more closely related
Unexpected Family Tree
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Currently, systematists use
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Structural, biochemical, fossil, and molecular comparisons to infer evolutionary
relationships
You
Your Cousin!
Morphological and Molecular Homologies
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In general, organisms that share very similar structures, breeding patterns or
similar DNA sequences
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Are likely to be more closely related than organisms with vastly different
structures or sequences.
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Not always true! Analogy vs. Homology
Homology
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Homologous Structures – structures in different species that are similar
because of common ancestry.
Analogy
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Analogous Structures – similarity in structures due to adaptations from similar
evolutionary pressures (convergent evolution) and not a common ancestor.
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Convergent evolution occurs when similar environmental pressures and
natural selection
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Produce similar (analogous) adaptations in organisms from different evolutionary
lineages
Australian Mole –
marsupial mammal
North American Mole –
placental mammal
Sorting Homology from Analogy
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A potential misconception in constructing a phylogeny
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Is similarity due to convergent evolution, called analogy, rather than shared
ancestry
Ex: Humans, gorillas, and ravens have the ability to problem-solve, and are highly
intelligent. Humans and gorillas share ancestry: homology. Ravens are in a
separate phylum (birds), so developed their intelligence separately from humans.
Linking Classification and Phylogeny
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Systematists depict evolutionary
relationships
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In branching phylogenetic trees
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Each branch point
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Represents the divergence of two species
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“Deeper” branch points
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Represent progressively greater amounts of divergence
“KLADOS” = Greek word meaning “BRANCH” or
“SPROUT”
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Cladogram - a shows pattern of shared, inherited characteristics; a “graphic
organizer” based on measurable traits and not evolutionary relationships.
Cladogram for Transportation
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Wheels are the most
ancestral (oldest).
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Wings are the most
derived (newest).
Construct a Cladogram for Us!
Gorilla
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Four limbs
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Fur
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No tail
Tiger
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Four limbs
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Fur
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Tail
Lizard
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Four limbs
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Tail
Fish
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Tail
Chimpanzee
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Four limbs
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Fur
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No tail
Clade With 4 Limbs
Clade With Fur
Clade With No Tail
Characteristics (Traits) for
Constructing this Cladogram
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Tail is the most ancestral
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Four limbs is the oldest derived trait
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Fur is a later derived trait
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Loss of tail is the most derived trait
One Possible Cladogram
Four Limbs
Where’s the Tail?
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How do we know the gorilla and chimpanzee
have lost their tail?
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Sometimes cladists must compare
embryological development and internal
anatomy to determine relatedness.
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May not be exactly the same structures.
Coccyx- Primate Vestigial Tails
Gorilla Pelvic Girdle
Human Pelvic Girdle
Vestigial Structure - historical remnants of a structure
that has little or no use in a modern organism but had
a function in ancestors.
A Vertebrate Cladogram
Lancelet
Vertebrae
Birds
Mammals
Reptile
Feathers
Amphibian
Fur
Fish
Endothermic
Lancelet
Amniotic Egg
Four Limbs
Vertebrae
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What is the shared primitive character for
this clade?
Ans:
Birds
Reptile
Mammals
Feathers
Amphibian
Fur
Fish
Endothermic
Lancelet
Amniotic Egg
Four Limbs
Vertebrae
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What is the shared derived
character for amphibians,
reptiles, birds & mammals?
Ans: Four Limbs
For reptiles, birds &
mammals?
Ans: Amniotic Egg
Phylogenetic Trees and Timing
A cladogram is not a phylogenetic tree; may need more
information (fossils, molecular systemics, etc.).
 Any chronology represented by the branching pattern of
a phylogenetic tree
 Is relative rather than absolute in terms of
representing the timing of divergences.
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Phylograms
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In a phylogram:
The
length of a
branch reflects the
number of genetic
changes that have
taken place in a
particular DNA or
RNA sequence in
that lineage.
A phylogram of homologous
hedgehog genes.
Outgroup
Ultrametric Trees
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In an ultrametric tree:
The
branching
pattern is the
same as in a
phylogram, but
all the branches
that can be
traced from the
common
ancestor to the
present are of
equal length.
Outgroup
A Rule about Phylogenetic Trees
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William of Ockham – 14th Cent. English
philosopher, stated that, when all qualities of
hypotheses are equal, the simplest
explanation for a phenomenon is usually
correct; Occam’s Razor: "entities must not
be multiplied beyond necessity" (entia non
sunt multiplicanda praeter necessitatem).
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Parsimony – stingy, economical, fewest
complications.