Biology 2900 Principles of Evolution and Systematics

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Biology 2900Principles of Evolutionand
Systematics

• Dr. David Innes
• Jennifer Gosse
• Valerie Power

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Announcements

• Lab 4 Group 2 starts Monday, March 10
• Download from Webpage
• Pass in a copy of article used for Lab 5
  presentation ( 2 marks)

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Evolution in the News

• Globe and Mail

Darwin the Evolution Revolution March 8 to
August 4, 2008Garfield Weston Exhibition
HallThe most in-depth exhibition ever mounted on
Charles Darwin!
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Topics

• Diversity
• Classification and phylogeny (Lab 4)
• Species and speciation
• Patterns of evolution
• Evolution in the fossil record
• History of life on earth
• The geography of evolution
• The evolution of biodiversity

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Species and Speciation

• Species (Ch. 15)
• What Are Species?
• Barriers to Gene Flow
• How Species Are Diagnosed
• Differences among Species
• Genetic Basis of Reproductive
• Barriers
• Molecular Divergence among
• Species
• Hybridization

Speciation (Ch. 16) Modes of
Speciation Allopatric Speciation
Alternatives to Allopatric Speciation
Polyploidy and Recombinational
Speciation How Fast Is Speciation?
Consequences of Speciation
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Modes of Speciation
Gene flow

• Allopatric isolated populations geographic
  barrier
• Peripatric peripheral isolated population
  founder effect
• Parapatric neighbouring populations
• Sympatric single population

X
X
?
? ??
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Vicariance Separation of a population by a
barrier to gene flow
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Allopatric Speciation

• Allopatry defined by the reduction in movement
  of
• individuals or gametes
• Genetic divergence occurs forming new species
• Range expansion ? secondary ? reinforcement of
• contact
  prezygotic RIB
• Thought to be the most common mode of
  speciation

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Allopatric Speciation

• Hawaii
• Achatinella tree snails

YouTube Allopatric Speciation
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Evolution of Reproductive Isolation
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Ecological Speciation

• A form of allopatric speciation
• Association between ecological adaptation and
  reproductive isolation
• Example Three-spined sticklebacks
• Gasterosteus

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Ecological Speciation

• Parallel speciation Ecomorphs
• benthic (bottom-feeding)
• limnetic (open water)

Mating preference
Dolph Schluter UBC
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Sympatric Speciation

• Speciation with gene flow
• Controversial limited evidence
• Insect host races - adaptation
• Native host Hawthorn --- host shift to apples
• Rosaceae

Apple maggot Rhagoletis pomonella
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Rate of Speciation

• Various approaches for estimating
• Rates vary greatly
• Mutation and drift ? very slow
• Natural selection ? faster
• Geological evidence
• Big Island of Hawaii 800,000 years
• Endemic Drosophila species

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Hawaiian Drosophila (adaptive radiation)
http//www.bio.ilstu.edu/Edwards/HawaiianDrosophil
a/index.shtml
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Biological Speciation Interval Time for
Speciation
Net speciation speciation - extinction
Rate of Speciation
Millions of Years
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Consequence of Speciation

• Biological Diversity
• "Without speciation, there would be no
  diversification.no adaptive radiation.
• The species is the keystone of evolution "
• Ernst Mayr (1963)

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Topics

• Diversity
• Classification and phylogeny (Ch. 2)
• Species and speciation (Ch. 15, 16)
• Patterns of evolution (Ch. 3)
• Evolution in the fossil record
• History of life on earth
• The geography of evolution
• The evolution of biodiversity

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Patterns of Evolution

• Topics
• Evolutionary History
• History of Character Evolution
• Evolutionary Trends
• Adaptive Radiation

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Evolutionary History

• Phylogenies Provide
• 1. Branching relationships among taxa
• 2. History of change in characteristics
• in the absence of ___________
• Many characteristics leave no _______
• What sorts of characters?

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Fig. 3.1
What common feature unites the great apes? The
term is __________
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Patterns of Evolution

• Example Observed genome size variation
• Is there
• any pattern?
• What is it?

Fig. 19.7
Complexity
Genome Size (pg of DNA)
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Evolutionary History and Classification

• Major features of evolution
• Cladogenesis branching
• Anagenesis change within descendants
• Anagenesis often the result of
  adaptation
• Difficult to combine cladogenesis and anagenesis
  in a classification. Why?
• Example?

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Evolutionary History and Classification

• Cladistic Systematics
• Classification based on monophyletic groups
• and the abolition of paraphyletic taxa
• Taxa Monophyletic
• Paraphyletic
• Polyphyletic
• Example?

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Taxon
?
?
?
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Example

• Class Reptilia (reptiles)
• air-breathing, cold-blooded vertebrates
• skin covered in scales
• tetrapods (descended from vertebrates with
  four limbs)
• amniotes (embryos surrounded by an amniotic
  membrane)
• Why is Reptilia considered paraphyletic?
• How can it be made monophyletic?

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History of Character Evolution

• Character mapping
• Phylogeny used to infer the history of
  evolutionary change of characteristics
• Map character state changes on tree such that the
  homoplasy is minimized

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Two vertebrates lacking legs
Snake
Caecilians (Amphibian)
Loss of legs An example of________
Tetrapods
Snakes
Common ancestor
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Patterns of Evolutionary Change

• Features are modified from pre-existing features
• example of __________
• Homoplasy is common (example__________)
• 3. Homoplasy often initial evidence for
  adaptive significance of feature Example ?

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Hummingbird
South American honey creeper
Sunbird (Africa)
Hawaiian honey creeper
Australian honeyeater
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Patterns of Evolutionary Change

• 4. Rates of Character evolution differ (Examples)

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Patterns of Evolutionary Change

• 5. Evolution often gradual (gradualism)

Male flies Species of Zygothrica
Sandpiper species
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Patterns of Evolutionary Change

• 6. Change in form correlated with change in
  function

Ichneumon wasp ovipositor
Wasp stinger
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Patterns of Evolutionary Change

• 7. Species similarities change during ontogeny

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Patterns of Evolutionary Change

• 8. Development and patterns of morphological
  evolution
• - based on an analysis of embryonic
  development
• a. Individualization serial homology
• b. Heterochrony paedomorphosis
• c. Allometry allometric growth

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Allometry

• Allometric growth differential rate of growth
  of different parts of an organism during ontogeny

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Allometry
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Patterns of Evolutionary Change

• 9. Increases and decreases in complexity

stigmas
anthers
Evolutionary Trends
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Patterns of Evolutionary Change

• 1. Features are modified from pre-existing
  features
• 2. Homoplasy is common
• 3. Homoplasy ?evidence for adaptation
• 4. Rates of character evolution differ
• 5. Evolution often gradual (gradualism)
• 6. Change in form correlated with change in
  function
• 7. Species similarities change during ontogeny
• 8. Development and patterns of morphological
  evolution
• 9. Increases and decreases in complexity
• 10. Many clades display Adaptive Radiation

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Adaptive Radiation

• Divergent evolution of numerous related lineages
  over a relatively short time period
• Examples 1. Galapagos finches
• 2. Hawaiian silverswords
• 3. African Cichlid fish

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Adaptive radiation in Hawaiian Silverswords
Diversity of life forms herbs, shrubs, trees
Link All species genetically very similar but
morphologically different
Evolved from a small herbaceous ancestor
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Adaptive Radiation in African Cichlid Fishes
Species Lists
est. of species Lake
Victoria gt200 Lake Tanganyika gt140 Lake
Malawi 500 - 1000
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Summary

• Phylogeny (based on gene sequences)
• Species characteristics (morphology etc.)
• Describes past changes among species

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Topics

• Diversity
• Classification and phylogeny (Ch. 2)
• Species and speciation (Ch. 15, 16)
• Patterns of evolution (Ch. 3)
• Evolution in the fossil record (Ch. 4)
• History of life on earth
• The geography of evolution
• The evolution of biodiversity

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Evolution in the Fossil Record

• Living organisms ? History of evolution
• Fossils ? direct evidence of evolution
• Paleontology
• - documents details of evolutionary history
• What else does paleontology tell us?

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Books on fossil hunting
The Bone Hunters Heroic Age of Palaeontology in
the American West by Url Lanham
Donald Johanson (1982)
David Wallace
Lucy Austalopithecus afarensis
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Evolution in the Fossil Record

• Topics
• Geology
• The fossil record
• Evolutionary trends
• Rates of evolution

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Geology

• Rocks Igneous
• Sedimentary
• Metamorphic
• Most fossils found in which rocks?

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Geological Time Scale

• Most eras and periods named before Darwins time
• Geological eras and periods
• identified by distinctive fossils
• Boundaries marked by changes in fossil
  composition

Map
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Geological Time Scale

• Phanerozoic
• Myr Eras Periods
• 66 - Cenozoic Quaternary, Tertiary
  (Epochs)
• 251 - 145 Mesozoic Cretaceous, Jurassic,
  Triassic
• 542 - 299 Paleozoic Permian, Carboniferous,
  Devonian, Silurian, Ordovician, Cambrian
• ----------------------
• 2500 Proterozoic trace fossils earliest
  eukaryotes
• Archean earliest life (prokaryotes)

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Geological Time Scale

• Futuyma Every student of evolution should
  memorize the sequence of eras and periods as well
  as a few key dates
• Beginning of
• Paleozoic era (Cambrian period) 542 Mya
• Mesozoic era (Triassic period) 251 Mya
• Cenozoic era (Tertiary period) 65.5 Mya