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Biology 2900 Principles of Evolution and Systematics

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Title: Biology 2900 Principles of Evolution and Systematics


1
Biology 2900Principles of Evolutionand
Systematics
  • Dr. David Innes
  • Jennifer Gosse
  • Valerie Power

2
Final Exam
  • Friday April 18, 2008
  • 900 1100 am IIC 2001

3
Final Exam Topics
  • 1. Revised questions from midterm
  • 2. Life-history evolution
  • 3. Diversity
  • Classification and phylogeny
  • Species and speciation
  • Patterns of evolution
  • Evolution in the fossil record
  • History of life on earth
  • The evolution of biodiversity

4
Final Exam Format
  • Multiple choice
  • True/False
  • Fill in the blank
  • Matching
  • Example Questions

5
Topics
  • Adaptation
  • Reproduction
  • Sex and Sexual Selection
  • Life-history evolution (Ch. 17)
  • 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 (Ch. 5)
  • The evolution of biodiversity (Ch. 7)

6
  • Life History Evolution
  • Evolution by natural selection has modified all
    organisms for one ultimate task
  • to reproduce
  • How organisms carry out this task
  • enormously diverse

7
  • Life History Evolution
  • Organisms cant
  • - mature at birth
  • - produce high-quality offspring
  • in large
    numbers
  • - live forever
  • Energy available for each activity finite
  • trade-offs

and
and
8
  • Life History Evolution
  • Attempts to explain the diversity of
    reproductive strategies
  • Trade-offs constrain the evolution of
    adaptations
  • Balance costs and benefits to maximize
    reproductive success

9
  • Life History Evolution
  • Environmental variation the source of much of the
    observed life-history variation
  • Diversity of ways of surviving and reproducing
  • Questions
  • 1. Why do organisms age and die ?
  • 2. How many offspring should be produced
    ?
  • 3. How big should each offspring be ?

10
  • Theories of Aging and Senescence
  • 1. Rate-of-living theory
  • 2. Evolutionary theory

11
  • 2. How many offspring to produce?
  • Trade-off fixed amount of energy and time
  • - the more offspring produced, the less time
    and energy to devote to each one

12
  • 3. How big should each offspring be?
  • Trade-off fixed amount of energy
  • many small offspring or few large offspring
  • Size number trade-off

13
Topics
  • Adaptation
  • Reproduction
  • Sex and Sexual Selection
  • Life-history evolution (Ch. 17)
  • 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 (Ch. 5)
  • The evolution of biodiversity (Ch. 7

14
Phylogeny
  • Genealogical relationship among organisms
  • - share a recent common ancestor
  • - share more distant common ancestors
  • Phylogeny estimated, reconstructed,
    assembled

15
Terms (Futuyma Ch. 2)
  • Plesiomorphic Character states
  • Apomorphic Ancestral
  • Synapomorphic Derived
  • Autapomorphic Convergent
  • Homology Reversal
  • Homoplasy Outgroup
  • Parsimony Sister group
  • Polytomy Nodes
  • Taxa (Taxon) Common Ancestor
  • Monophyletic Polyphyletic

16
Phylogeny
  • Inferring phylogenetic history
  • Species become steadily more different from one
    another
  • Therefore,
  • Can infer history of branching by measuring
    degree of similarity or difference

17
Character States
  • Each character can occur as different forms
  • 1. a c g t c g g a g a c g a c g g a g
  • 2. Turtle shell shape
  • 3. Neck length

1 2 3 4 5 6 7 8
9
1 2 3 4 5 6 7
8 9
rounded saddle
long short
18
Phylogenetic Analysis
  • Example (Fig. 2.4) 4 taxa (species)
  • Arrange into a phylogenetic tree
  • Which species derived from
  • - recent common ancestors
  • - ancient common ancestors

19
Phylogenetic Analysis
  • Characters ? 10 a j
  • States 0 ancestral
  • 1 derived (has evolved 0 ? 1)
  • Plesiomorphic ancestral
  • Apomorphic derived
  • Data on character states used to infer
    phylogenetic relationships

20
(A)
Monophyletic groups Sp2 Sp3 Sp2
Sp3Sp1 Sp2Sp3Sp1Sp4
21
Phylogenetic Analysis
  • Interpretation
  • Taxa similar because they share
  • ancestral derived character states
  • But, only shared derived states (synapomorphies)
  • indicate monophyletic groups
  • Also,
  • derived states restricted to a single lineage
    (autapomorphies)? no indication of relationship

22
Phylogenetic Analysis
  • Further complications
  • Homoplasy (homoplasious)
  • - convergence a character state independently
    evolved two or more times (ie. does not have a
    unique origin)
  • - reversals derived state evolves back to
    ancestral

23
Phylogenetic Reconstruction
  • Principle of Parsimony
  • - the simplest explanation
  • - requiring the fewest undocumented
    assumptions
  • preferred over
  • - more complicated explanations
  • - requiring more assumption
  • - for which evidence is lacking
  • Phylogenetic relationship (Tree)
  • best estimate requires fewest evolutionary
    changes

24
Phylogenetic Analysis Example
  • Based on Morphology
  • Hominoidea monophyletic
  • Families
  • Hylobatidae (gibbons)
  • Pongidae (great apes)
  • Orangutan, Gorilla, Chimpanzee, Bonobo
    (Pygmy Chimp)
  • Hominidae (humans)
  • Homo sapien (H. erectus, H.
    ergaster, H. rudolfensis, H. habilis)

25
(E) Humans
Pongidae monophyletic
26
New classification of apes and humans
  • Tree of Life

Family Hominidae
27
Molecular Clocks
  • DNA sequences appear to evolve and diverge
  • at a constant rate (clock like).
  • Phylogeny relative times of divergence
  • Molecular clock Fossil data absolute
    times
  • of divergence
  • Calibrate clock for a particular sequence
  • Estimate divergence times for taxa with no
    fossil
  • record

28
Difficulties in Phylogenetic Analysis
  • Scoring characters is difficult
  • Homoplasy is very common
  • Traces of prior evolutionary history often erased
  • Rapid divergence lack of synapomorphies
  • Estimate of gene tree may produce incorrect
    species phylogeny
  • Hybridization and horizontal gene transfer

29
Phylogenetic ReconstructionSummary
  • Active area of research to improve accuracy
  • - molecular methods
  • - statistical methods
  • Provide estimates of evolutionary history
    for a group of organisms
  • Infer history of changes in organisms
    characteristics (adaptation)
  • Test evolutionary hypotheses

30
Topics
  • Adaptation
  • Reproduction
  • Sex and Sexual Selection
  • Life-history evolution (Ch. 17)
  • 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 (Ch. 5)
  • The evolution of biodiversity (Ch. 7

31
Species
  • Species form the bridge between the evolution of
    populations and the evolution of taxonomic
    diversity
  • Cladogenesis branching of lineages
    (Speciation)
  • Anagenesis evolution within species
  • Speciation origin of biodiversity

32
Speciation
  • Speciation (branching) useful for
  • 1. inferring phylogenetic relationships
    among
  • living taxa
  • 2. tracing evolution of characteristics on
  • phylogenetic trees

33
Consequence of Speciation
  • Different species undergo independent divergence
  • Rate of Speciation full history of speciation
    process
  • - too prolonged (slow) to study directly
  • - too fast to be fully documented in the
    fossil record
  • Therefore, the study of speciation based on
    living species

34
What are Species?
  • Group of individuals that conform to a type based
    on certain morphological characters
  • Problems Morphological variation within and
    among populations
  • Species concept must be able to accommodate
    variation

35
Biological Species Concept (BSC)
  • Most frequently used by evolutionary
  • biologists
  • Defined by Ernst Mayr (1942)
  • Species are groups of actually or potentially
    interbreeding populations which are
    reproductively isolated from other such groups

36
Barriers to Gene Flow
  • Table 15.2
  • Premating barriers prevent (or reduce)
    combining of
  • gametes
    between species
  • Postmating, prezygotic gametes combine but no
    zygote

  • formed
  • Postzygotic hybrid zygotes formed but have
    reduced
  • fitness
  • Any of these barriers may be incomplete

37
Diagnosis of Species
  • Species distinguished phenotypically (morphology)
  • Phenotypic characters serve as markers for
  • reproductive isolation
  • Molecular markers can provide a clearer
  • indication of reproductive isolation

38
Differences among Species
  • Differences
  • - directly responsible for reproductive
    isolation
  • - adaptive differences related to ecological
    factors
  • - neutral due to mutation and genetic drift
  • Differences evolved
  • - in populations before speciation
  • - during the speciation process
  • - after reproductive isolation
    (speciation)

39
Drosophila willistoni Complex 36
enzyme protein loci
Fixed for different alleles
Similar allele frequencies at most loci
40
The Genetics of Speciation
  • Process of divergence continuous
  • (gradual speciation).
  • 2. Substantial degree of genetic differentiation
    after the first stage. Genetic differentiation
    can become more pronounced after reproductive
    isolation. (drift, selection)

Identity 0.970 0.795 0.517
0.352
41
The Genetics of Speciation
  • 3. Speciation does not involve a major
  • reorganization of the genome
  • 4. Reproductive isolation may involve only a
  • few loci

42
Reproductive Isolation
  • Stages of speciation (allopatric)
  • 1. Isolation
  • 2. Genetic Divergence (selection, drift,
    mutation)
  • - reproductive isolation evolves as a
    byproduct
  • 3. Secondary contact test of reproductive
    isolation

43
Genetic Differences
  • Genetic differences continue to accumulate long
    after two species become reproductively isolated
  • Difficult to identify isolation barriers and
    genetic difference involved in the original
    speciation
  • Need to compare populations that have only
    recently become reproductively isolated.

44
Hybridization
  • Hybridizing populations
  • - represent intermediate stages in the
  • process of speciation
  • - opportunities to study speciation

45
Hybridization
  • Hybrid Zones
  • - Secondary contact between closely related
    species
  • - Hybrid zone with some offspring of mixed
    ancestry
  • - Cline?for characters across hybrid zone

46
Fate of Hybrid Zones
  • Persist indefinitely
  • Natural selection enhances prezygotic isolation
    full reproductive isolation (no hybrids)
  • Increased mating two species merge
  • Hybrid speciation

47
Modes of Speciation
Gene flow
  • Allopatric isolated populations geographic
    barrier
  • Vicariance
  • Peripatric peripheral isolated population
    founder effect
  • Parapatric neighbouring populations
  • Sympatric single population

X
X
?
? ??
48
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

49
Ecological Speciation
  • A form of allopatric speciation
  • Association between ecological adaptation and
    reproductive isolation
  • Example Three-spined sticklebacks
  • Gasterosteus

50
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
51
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)

52
Topics
  • Adaptation
  • Reproduction
  • Sex and Sexual Selection
  • Life-history evolution (Ch. 17)
  • 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 (Ch. 5)
  • The evolution of biodiversity (Ch. 7

53
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

54
Patterns of Evolutionary Change
  • 1. Features are modified from pre-existing
    features
  • 2. Homoplasy is common
  • 3. Homoplasy ?evidence for adaptation
    (convergence)
  • 4. Rates of character evolution differ (mosaic
    evolution)
  • 5. Evolution often gradual (gradualism)
  • 6. Change in form correlated with change in
    function
  • 7. Species similarities change during ontogeny
  • 8. Development influences patterns of
    morphological evolution
  • 9. Increases and decreases in complexity
  • 10. Many clades display adaptive radiation

55
Summary
  • Phylogeny (based on gene sequences)
  • Species characteristics (morphology etc.)
  • Describes past changes among species

56
Topics
  • Adaptation
  • Reproduction
  • Sex and Sexual Selection
  • Life-history evolution (Ch. 17)
  • 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 (Ch. 5)
  • The evolution of biodiversity (Ch. 7

57
Evolution in the Fossil Record
  • Living organisms ? History of evolution
  • Fossils ? direct evidence of evolution
  • Paleontology
  • - documents details of evolutionary history
  • - absolute time scale of evolutionary events
  • What else does paleontology tell us?

58
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)

Precambrian
59
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
  • Cenozoic era (Tertiary period) 66 Mya
  • Mesozoic era (Triassic period) 251 Mya
  • Paleozoic era (Cambrian period) 542 Mya

60
Geological Time Scale
  • Mya Cenozoic
  • 2 Quaternary
  • 66 Tertiary
  • Mesozoic
  • 145 Cretaceous
  • 200 Jurassic
  • 251 Triassic
  • Paleozoic
  • 299 Permian
  • 359 Carboniferous
  • 416 Devonian
  • 444 Silurian
  • 488 Ordovician
  • 542 Cambrian
  • 2500 Proterozoic
  • Archean

Mnemonic Prince Charles Devoured Several Old
Cabbages
61
The Fossil Record
  • Does the fossil record provide evidence for
  • 1. evolutionary change
    (Descent with modification)?
  • 2. gradual evolution, as
    proposed by Darwin?
  • Examples
  • Evolutionary changes within
    species
  • Origins of higher taxa
  • Birds
  • Cetacea (whales and
    dolphins)
  • Hominins

62
Evolution in the Fossil Record
  • Summary
  • Fossil record incomplete
  • Characters often evolve gradually
  • Origin of higher taxa documented in fossil record
  • (birds, cetaceans, Homo)
  • Changes in form associated with change in
    function
  • Relative times of origin phylogeny fossils
  • Evolutionary trends (some reversal)
  • Rates of evolution very variable

63
Topics
  • Adaptation
  • Reproduction
  • Sex and Sexual Selection
  • Life-history evolution (Ch. 17)
  • 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 (Ch. 5)
  • The evolution of biodiversity (Ch. 7

64
History of Life
  • Temporal aspects Questions
  • What types of organisms were found during
    different
  • geological time periods?
  • 2. When did different groups of organisms
    dominate?
  • 3. When did different organisms go extinct?
  • 4. When did the ancestors of living organisms
    originate?

65
Beginning of each Era (Mya)
Phanerozoic
66
Emergence of Life
  • Steps in the origin of life
  • Simple organic molecules
  • produced by abiotic chemical
  • reactions
  • Formed polymers that
  • could self-replication (RNA-like)
  • Natural selection and evolution can
  • occur in nonliving replicating molecules

67
Precambrian Life
  • Arachean Proterozoic Precambrian lt 542 Mya
  • Oldest definitive evidence of life 3.5 billion
    years ago
  • - bacteria-like microfossils (stromatolites)
  • Domains of life Eucarya (Eukaryotes)
  • Archaea Bacteria
    (Prokaryotes)
  • For 2 billion years only life
    Prokaryotes
  • Evolution of Life

68
Domains of Life
  • Archaea many anaerobic and found in extreme
    environments
  •  
  • Bacteria diverse metabolic capacities including
    photosynthesis
  •  
  • Eukaryotes cytoskeleton, nucleus with distinct
    chromosomes,
  • mitotic spindle
  • almost all have
    mitochondria and some have
  • chloroplasts

69
Temporal Variation in Diversity
  • Mya Cenozoic
  • 2 Quaternary Glaciations,
    extinctions of large mammals birds Homo sapiens
  • 66 Tertiary Radiations birds,
    mammal, snakes, angiosperms, insects, teleost
    fishes
  • Mesozoic
  • 145 Cretaceous Radiation of dinosaurs
    diversification of mammals, birds, angiosperms
    extinction of dinosaurs
  • 200 Jurassic Diverse dinosaurs
    first birds archaic mammals gymnosperms
    evolution of angiosperms
  • 251 Triassic Gymnosperms dominate,
    diverse reptiles, first dinosaurs, first
    mammals
  • Paleozoic
  • 299 Permian Advanced fishes,
    diverse insects, amphibians decline, mammal-like
    reptiles, major mass extinctions
  • 359 Carboniferous Early vascular plants
    (ferns), early winged insects, diverse
    amphibians, first reptiles
  • 416 Devonian Diverse bony fishes,
    trilobites, origin of ammonoids, amphibians,
    insects, ferns, seed plants extinctions
  • 444 Silurian Diverse agnaths
    origin of jawed fished, early terrestrial
    vascular plants, arthropods, insects
  • 488 Ordovician Diverse echinoderms,
    other invertebrates, agnathan vertebrates mass
    extinctions
  • 542 Cambrian Diverse marine animals
    first appears of most animal phyla earliest
    agnathan vertebrates diverse algae
  • 2500 Proterozoic Earliest eukaryotes,
    multicellular animals (possible cnidaria,
    annelids, arthropods)
  • uncertain Archean Origin of life
    photosynthesis generates oxygen evolution of
    aerobic respiration

From Table 4.2 Futuyma
70
Summary
  • Life originated from a single common ancestor
  • Earliest life prokaryotes 3.5 billion years
    ago
  • Eukaryotes 1.5 billion years ago (Mitochondria
    and Chloroplasts)
  • Cambrian explosive diversification of life (542
    mya)
  • Land plants and arthropods Silurian, Devonian,
    carboniferous
  • Permian mass extinction
  • Mesozoic era seed plants, insects, dinosaurs,
    mammals
  • Cretaceaous/Tertiary (K/T) mass extinction
  • Pleistocene glaciations
  • Current human induced mass extinctions??????

71
Topics
  • Adaptation
  • Reproduction
  • Sex and Sexual Selection
  • Life-history evolution (Ch. 17)
  • 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 (Ch. 5)
  • The evolution of biodiversity (Ch. 7

72
The Evolution of Biodiversity
  • Estimating changes in taxonomic diversity
  • Taxonomic diversity through the Phanerozoic
  • - rates of origination and extinction
  • - causes of extinction
  • - mass extinctions (causes, victims,
    survivors)
  • - origination and diversification
  • - the role of environmental change

73
Phanerozoic Taxonomic Diversity
  • Most complete fossil record
  • - marine animals with shells or skeletons
  • - data set 4,000 families 20,000 genera

Since the Triassic rates of origin gt rate of
extinction
Mass extinctions
74
Phanerozoic Taxonomic Diversity
Mostly flowering plants
Mostly birds and mammals
75
Probability of Extinction
Constant probability of extinction Organisms
constantly exposed to new environmental
changes, each with a risk of extinction Red
Queen Hypothesis - environment constantly
deteriorating because of the evolution of
other organisms (competitors, predators,
parasites continue to evolve) - each species
must continue to evolve to avoid
extinction. Constant probability of going extinct.
76
Mass Extinctions
  • Five mass extinctions
  • End of Ordovician
  • Late Devonian
  • Permian/Triassic (end-Permian)
  • End of Triassic
  • Cretaceous/Tertiary (K/T) - dinosaurs

77
Summary
1. Analysis of diversity in the fossil record
requires corrections
2. Marine animals rapid increase in diversity
beginning of Cambrian - Other groups also showed
increases in diversity during Mesozoic
3. Background extinction rate declined taxa
prone to extinction became extinct early
4. Five major mass extinctions impact of extra-
terrestrial body?
5. Survival of mass extinctions species with
broad geographic and ecological distributions
78
Summary
6. Newly diversifying groups displace other
taxa by competitive exclusion or by competitive
release following extinction
7. Increase in diversity due to adaptation to new
ecological niches facilitated by key adaptations
8. Rates of both extinction and origination
diversity-dependent. Tends to stabilize diversity.
9. Next mass extinction has already begun.
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