Biology 2900 Principles of Evolution and Systematics - PowerPoint PPT Presentation

Loading...

PPT – Biology 2900 Principles of Evolution and Systematics PowerPoint presentation | free to view - id: 69194-ZDc1Z



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Biology 2900 Principles of Evolution and Systematics

Description:

'presence of a dorsal fin' Whales and Tuna form a monophyletic groups ... (only dorsal fin homoplasious due to ?) Phylogenetic Reconstruction Using Parsimony ... – PowerPoint PPT presentation

Number of Views:54
Avg rating:3.0/5.0
Slides: 52
Provided by: david146
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Biology 2900 Principles of Evolution and Systematics


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

2
Announcements
  • Lab 4 Group 1 starts Monday, March 3
  • Download from Webpage
  • Pass in a copy of article used for Lab 5
    presentation ( 2 marks)

3
Encyclopedia of life
YouTube Video
E. O. Wilson
4
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

5
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

6
Darwin and Evolution
  • All living organisms related
  • Phylogenetic Tree
  • - ancestor - descendant

7
Phylogenetic Tree
  • Tree-like Phylogeny
  • Consequence of a branching process
  • D
  • B
  • - single species A E
  • F
  • C
  • G

Descendants evolve differences Process repeated
over millions of years
8
Plants
Eucarya
Fig. 2.1 The Tree of Life http//www.tolweb.org/
Animals
Root
Archaea
Bacteria
9
Phylogeny
  • Genealogical relationship among organisms
  • - share a recent common ancestor
  • - share more distant common ancestors
  • Phylogeny estimated, reconstructed,
    assembled

10
Phylogeny
  • Useful for understanding
  • Which organisms share a common ancestor
  • Pathway by which characteristics have evolved
  • (adaptation)

11
Phylogeny
  • Evolutionary history
  • - not observed directly
  • - can not know the true evolutionary
    history
  • - deduced from evidence
  • some fossil, but mostly living
    organisms

12
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

13
Characteristics of Organisms
  • Phenotypic characters
  • - external and internal morphology
  • - behaviour, physiology, biochemistry
  • DNA sequences acgtcggagcctt
  • - nucleotide site in a sequence a character

14
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
15
Phylogenetic Analysis
  • Example (Fig. 2.4) 4 taxa (species)
  • Arrange into a phylogenetic tree
  • Which species derived from
  • - recent common ancestors
  • - ancient common ancestors

16
Phylogenetic Analysis
  • Characters
  • (A)
  • Species 1 0 0 1 1 1 0 0 0 0 0
  • Species 2 0 0 1 0 0 1 1 1 1 0
  • Species 3 0 0 1 0 0 1 1 0 0 1
  • Species 4 1 1 0 0 0 0 0 0 0 0
  • Calculate similarity matrix of each pair
  • as shared character states

0 ancestral 1 derived
a b c d e f g h i j
17
(A)
Monophyletic groups Sp2 Sp3 Sp2
Sp3Sp1 Sp2Sp3Sp1Sp4
0 ? 1 Evolved
18
Phylogenetic Analysis
  • Ancestral and derived character states known
  • Two types of similarity
  • 1. Overall similarity
  • shared ancestral shared derived
  • 2. Shared derived (Synapomorphies)
  • count only shared characters
  • that evolved

19
Phylogenetic Analysis
  • Phylogeny in
  • Fig. 2.4 (A) Approximately equal rates of
    evolution along branches
  • Fig. 2.4 (B) Complications
  • Accelerated evolution in one branch
  • Consequence overall similarity indicates
    Sp1
  • and Sp3 most similar
  • Suggests they share a most recent common
    ancestor

20
(B)
Other autapomorphies?
Autapomorphy Derived in single lineage No
indication of relationship
Accelerated rate of evolution Suggests Sp 1 and
Sp3 most similar
21
Phylogenetic Analysis
  • Phylogeny Fig. 2.4 (B) Complications
  • Overall similarity indicates Sp1 and Sp3 most
    similar
  • Suggests they share a most recent common
    ancestor
  • Similarity not an adequate indicator of
    relationship
  • (Degree of relationship relative recency
    of common ancestor
  • ? similarity)
  • However,
  • Shared derived characters does accurately
    indicate relationship

22
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

23
Phylogenetic Analysis
  • Previous examples each character changed once
  • (0 ?
    1)
  • Taxa sharing a character state
  • inherited without change from common ancestor
  • Homologous characters (states) shared through
    inheritance from a common ancestor

24
Phylogenetic Analysis
  • Phylogeny Fig. 2.4 (C) 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
  • Consequence taxa with shared homoplasious
    characters have not inherited it from their
    common ancestor

25
(C)
Spot the error!!
Autapomorphy ?
26
(C)
0 1 1 1 1 1 1 0 1 1
g and h evolved twice
3 homoplasious characters - g and h
convergence - j reversal
27
Phylogenetic Analysis
  • Further complications
  • Homoplasy misleading evidence about phylogeny
  • Fig. 2.4C
  • 1. characters g and j erroneously
    suggest
  • Sp 1 and Sp 3 closest
    relatives
  • 2. character h erroneously
    suggests
  • Sp 1 and Sp 2 a monophyletic
    group
  • only uniquely derived shared characters
    evidence for monophyletic groups

28
Phylogenetic Analysis
  • Fig. 2.4C
  • Contains homoplasious character states
  • but shared character states matrix
  • and shared derived character states matrix
  • both correctly group Sp 2 and Sp 3
  • Homework assignment construct character state
    data
  • in which
  • - homoplasy incorrectly groups Sp 1 and Sp 3
    based on
  • shared character states
  • - correctly groups Sp 2 and Sp 3 based on
    shared derived character states

29
Homework Assignment
0 ancestral 1 derived
  • Characters
  • Species 1 0 1 1 0 0 0 1 1 0 1
  • Species 2 0 1 1 1 1 1 0 1 0 0
  • Species 3 0 1 1 1 1 1 1 0 0 1
  • Species 4 1 0 0 0 0 0 0 0 0 0

a b c d e f g h i j
1 2 3 4
Shared
Shared derived
30
History of Classification and Phylogeny
  • Numerical Taxonomy (1963)
  • Classification (Phenetic)
  • - objective
  • - repeatable
  • - large number of different types of characters
  • - quantitative (based on distance or similarity
    matrix)
  • - computer data analysis
  • - produces a phenogram of overall similarity

Sokal and Sneath
31
Numerical Taxonomy
  • 22 species of the moss Didymodon
  • Can a phenogram (dendrogram) of overall
    similarity represent a phylogenetic tree?

Not the primary purpose and Only if equal rates
of evolution among branches assumed
32
History of Classification and Phylogeny
  • Cladistics (Lab 4)
  • Classification (Phylogenetic)
  • - Classification based on evolutionary
    relationships
  • - Character based (shared derived)
  • - Branching pattern from common ancestor
  • - Produces a cladogram of ancestors and
    descendants

33
Phylogenetic Analysis
  • Phylogenetic relationships
  • German entomologist Willi Hennig
  • Inferring phylogenetic relationships
  • Taxa similar because they share
  • - uniquely derived character states
    (Apomorphic)
  • - ancestral character states (Plesiomorphic)
    1913 - 1976
  • - homoplasious character states (Convergence,
    reversal)
  • But only similarity due to uniquely derived
    character states evidence for monophyletic groups

34
Systematics Journals
Systematic Botany
35
Monophyletic Groups
Uniquely derived character states -
Tetrapod limb - Amnion -
Feathers Define monophyletic groups -
Tetrapods - Amniotes -
Birds Lack of the character is the ancestral
state and does not provide phylogenetic
information (ie. Lack of feathers does not form
a phylogenetic group)
36
Phylogenetic Reconstruction
  • Monophyletic groups defined by uniquely derived
    character states
  • Difficulties
  • 1. How to determine which state
    is derived?
  • 2. How to determine if it is
    uniquely derived or
  • homoplasious?
  • Use the fossil record?
  • - interpreting the relationship between fossil
    and living species
  • - most species have very incomplete fossil
    records

37
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

38
Phylogenetic Reconstruction Using Parsimony
Hypothesis For the character presence of a
dorsal fin Whales and Tuna form a monophyletic
groups
of changes 17 (lots of homoplasy)
39
Phylogenetic Reconstruction Using Parsimony
Accepted Phylogeny
of changes 10 (only dorsal fin homoplasious
due to ?)
40
Phylogenetic Reconstruction Using Parsimony
  • the best phylogenetic hypothesis is the one
  • that requires the fewest homoplasious
  • changes

41
Maximum Parsimony
  • Example Fig. 2.7
  • Three species (1, 2, 3) form a monophyletic group
    relative to more distantly related outgroup
    species (4, 5).
  • What is the phylogenetic relationship among the
    3 species?
  • 3 possible trees

42
Three-Species Trees
outgroups
1 2 3 4 5
2 3 1 4 5
1 3 2 4 5
Tree 3
Tree 1
Tree 2
Sister 1 2 1 3
2 3 taxa
43
Character a C ?A (Why not A?C?)
b G?T c and d Define sp1 and sp2 as sister
groups e convergence f, g autapomorphies
Sister groups groups derived from a common
ancestor not shared with any other groups
44
Character a C ?A (not A?C) b
G?T c and d Define sp1 and sp2 as sister
groups e convergence f, g autapomorphies
Sister groups groups derived from a common
ancestor not shared with any other groups
45
Character a C ?A (not A?C) b
G?T c and d Define sp1 and sp2 as sister
groups e convergence f, g autapomorphies
Length (L) 8 character changes
Sister groups groups derived from a common
ancestor not shared with any other groups
46
c and d convegence
47
c and d convegence e reversal (T ? A? T)
48
Parsimony
  • Tree 1 best estimate
  • - shortest tree
  • - more characters support monophyly
  • of sp1 and sp2 (c and d)
  • than sp1 and sp3 (Tree 2) (e)
  • or sp2 and sp3 (Tree 3) (none)

49
Phylogenetic Methods
  • Other methods
  • Neighbor-joining
  • Maximum likelihood
  • Baysian
  • Software

50
Phylogenetic Methods
  • Online analysis
  • Biological Software
  • Data Fig. 2.4 A
  • 5 10
  • Ancestor 0000000000
  • species1 0011100000
  • species2 0010011110
  • species3 0010011001
  • species4 1100000000

1 2 3 4
51
Number of Phylogenetic Trees
  • One true phylogenetic tree
  • But many possible trees
  • 10 species how many trees?
  • Number of Trees
About PowerShow.com