1. 20
Phylogeny

2. Warm-Up Please complete the Socrative Self Evaluation Socrative.com
Room Code: ZABLOTSKY320

3. Overview: Investigating the Evolutionary History of Life
Legless lizards and snakes evolved from different lineages of lizards with legs
Legless lizards have evolved independently in several different groups through adaptation to similar environments 3

4. Figure 20.1
Figure 20.1 What kind of organism is this? 4

5. No limbs Eastern glass lizard Monitor lizard Iguanas ANCESTRAL Snakes
Figure 20.2
No limbs
Eastern glass lizard
Monitor lizard
Iguanas
ANCESTRAL
LIZARD
(with limbs)
Snakes
Figure 20.2 Convergent evolution of limbless bodies
No limbs
Geckos 5

6. Phylogeny is the evolutionary history of a species or group of related species
The discipline of systematics classifies organisms and determines their evolutionary relationships 6

7. Concept 20.1: Phylogenies show evolutionary relationships
Taxonomy is the ordered division and naming of organisms 7

8. Binomial Nomenclature
In the 18th century, Carolus Linnaeus published a system of taxonomy based on resemblances
Two key features of his system remain useful today: two-part names for species and hierarchical classification 8

9. The two-part scientific name of a species is called a binomial
The first part of the name is the genus
The second part, called the specific epithet, is unique for each species within the genus
The first letter of the genus is capitalized, and the entire species name is italicized
Both parts together name the species (not the specific epithet alone) 9

10. Hierarchical Classification
Linnaeus introduced a system for grouping species in increasingly broad categories
The taxonomic groups from narrow to broad are species, genus, family, order, class, phylum, kingdom, and domain 10

11. Kingdom: Animalia Domain: Bacteria Domain: Archaea Domain: Eukarya
Figure 20.3
Species: Panthera pardus
Genus: Panthera
Family: Felidae
Order: Carnivora
Class: Mammalia
Figure 20.3 Linnaean classification
Phylum: Chordata
Kingdom:
Animalia
Domain:
Bacteria
Domain:
Archaea
Domain:
Eukarya 11

12. A taxonomic unit at any level of hierarchy is called a taxon
The broader taxa are not comparable between lineages
For example, an order of snails has less genetic diversity than an order of mammals 12

13. Linking Classification and Phylogeny
Systematists depict evolutionary relationships in branching phylogenetic trees 13

14. Order Family Genus Species Felidae Panthera pardus (leopard) Panthera
Figure 20.4
Order
Family
Genus
Species
Felidae
Panthera
pardus
(leopard)
Panthera
Taxidea
taxus
(American
badger)
Taxidea
Carnivora
Mustelidae
Lutra lutra
(European
otter)
Lutra 1
Figure 20.4 The connection between classification and phylogeny
Canis
latrans
(coyote)
Canidae
Canis 2
Canis
lupus
(gray wolf) 14

15. Linnaean classification and phylogeny can differ from each other
Systematists have proposed that classification be based entirely on evolutionary relationships 15

16. Sister taxa are groups that share an immediate common ancestor
A phylogenetic tree represents a hypothesis about evolutionary relationships
Each branch point represents the divergence of two taxa from a common ancestor
Sister taxa are groups that share an immediate common ancestor 16

17. A polytomy is a branch from which more than two groups emerge
A rooted tree includes a branch to represent the most recent common ancestor of all taxa in the tree
A basal taxon diverges early in the history of a group and originates near the common ancestor of the group
A polytomy is a branch from which more than two groups emerge 17

18. where lineages diverge Taxon A
Figure 20.5
Branch point:
where lineages diverge
Taxon A 3
Taxon B
Sister
taxa 4
Taxon C 2
Taxon D 5
Taxon E
ANCESTRAL
LINEAGE 1
Taxon F
Figure 20.5 How to read a phylogenetic tree
Basal
taxon
Taxon G
This branch point
represents the common
ancestor of taxa A−G.
This branch point forms a
polytomy: an unresolved
pattern of divergence. 18

19. What We Can and Cannot Learn from Phylogenetic Trees
Phylogenetic trees show patterns of descent, not phenotypic similarity
Phylogenetic trees do not generally indicate when a species evolved or how much change occurred in a lineage
It should not be assumed that a taxon evolved from the taxon next to it 19

20. Applying Phylogenies
Phylogeny provides important information about similar characteristics in closely related species
Phylogenetic trees based on DNA sequences can be used to infer species identities
For example: A phylogeny was used to identify the species of whale from which “whale meat” originated 20

21. (Southern Hemisphere)
Figure 20.6
Results
Minke
(Southern Hemisphere)
Unknowns 1a,
2, 3, 4, 5, 6, 7, 8
Minke
(North Atlantic)
Unknown 9
Humpback
Unknown 1b
Blue
Figure 20.6 Inquiry: What is the species identity of food being sold as whale meat?
Unknowns 10,
11, 12, 13
Fin 21

22. Warm-Up 9/15/2016
Describe how phylogeny is used to understand relationships.

23. Concept 20.2: Phylogenies are inferred from morphological and molecular data
To infer phylogeny, systematists gather information about morphologies, genes, and biochemistry of living organisms
The similarities used to infer phylogenies must result from shared ancestry 23

24. Morphological and Molecular Homologies
Phenotypic and genetic similarities due to shared ancestry are called homologies
Organisms with similar morphologies or DNA sequences are likely to be more closely related than organisms with different structures or sequences 24

25. Sorting Homology from Analogy
When constructing a phylogeny, systematists need to distinguish whether a similarity is the result of homology or analogy
Homology is similarity due to shared ancestry
Analogy is similarity due to convergent evolution 25

26. Convergent evolution occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages 26

27. Figure 20.7
Figure 20.7 Convergent evolution of analogous burrowing characteristics 27

28. Bat and bird wings are homologous as forelimbs, but analogous as functional wings
Analogous structures or molecular sequences that evolved independently are also called homoplasies
Homology can be distinguished from analogy by comparing fossil evidence and the degree of complexity
The more complex two similar structures are, the more likely it is that they are homologous 28

29. Evaluating Molecular Homologies
Molecular homologies are determined based on the degree of similarity in nucleotide sequence between taxa
Systematists use computer programs when analyzing comparable DNA segments from different organisms 29

30. 1 C C A T C A G A G T C C 2 C C A T C A G A G T C C Figure 20.8-1
Figure Aligning segments of DNA (step 1) 30

31. 1 C C A T C A G A G T C C 2 C C A T C A G A G T C C Deletion 1 C C A T
Figure 1
C C A T
C A G A
G T C C 2
C C A T
C A G A
G T C C
Deletion 1
C C A T
C A G A
G T C C 2
C C A T
C A G A
G T C C
G T A
Insertion
Figure Aligning segments of DNA (step 2) 31

32. 1 C C A T C A G A G T C C 2 C C A T C A G A G T C C Deletion 1 C C A T
Figure 1
C C A T
C A G A
G T C C 2
C C A T
C A G A
G T C C
Deletion 1
C C A T
C A G A
G T C C 2
C C A T
C A G A
G T C C
G T A
Insertion 1
C C A T
C A
A G T C C
Figure Aligning segments of DNA (step 3) 2
G T A
C C A T
C A
A G T C C G 32

33. 1 C C A T C A G A G T C C 2 C C A T C A G A G T C C Deletion 1 C C A T
Figure 1
C C A T
C A G A
G T C C 2
C C A T
C A G A
G T C C
Deletion 1
C C A T
C A G A
G T C C 2
C C A T
C A G A
G T C C
G T A
Insertion 1
C C A T
C A
A G T C C
Figure Aligning segments of DNA (step 4) 2
G T A
C C A T
C A
A G T C C G 1
C C A T
C A
A G T C C 2
G T A G
C C A T
C A
A G T C C 33

34. Shared bases in nucleotide sequences that are otherwise very dissimilar are called molecular homoplasies 34

35. A C G G A T A G T C C A C T A G G C A C T A T C A C C G A C A G G T
Figure 20.9
A C G
G A T
A G T
C C A
C T A
G G C
A C T A
T C A
C C G
A C A
G G T
C T T
T G A
C T A G
Figure 20.9 A molecular homoplasy 35

36. Concept 20.3: Shared characters are used to construct phylogenetic trees
Once homologous characters have been identified, they can be used to infer a phylogeny 36

37. Cladistics Cladistics classifies organisms by common descent
A clade is a group of species that includes an ancestral species and all its descendants
Clades can be nested in larger clades, but not all groupings of organisms qualify as clades 37

38. A valid clade is monophyletic, signifying that it consists of the ancestor species and all its descendants 38

39. (a) Monophyletic group (clade) (b) Paraphyletic group
Figure 20.10
(a) Monophyletic group
(clade)
(b) Paraphyletic group
(c) Polyphyletic group A A A 1 1 B
Group I B B
Group III C C C D D D E E
Group II E 2 2
Figure Monophyletic, paraphyletic, and polyphyletic groups F F F G G G 39

40. (a) Monophyletic group (clade)
Figure 20.10a
(a) Monophyletic group
(clade) A 1 B
Group I C D
Figure 20.10a Monophyletic, paraphyletic, and polyphyletic groups (part 1: monophyletic) E F G 40

41. A paraphyletic grouping consists of an ancestral species and some, but not all, of the descendants41

42. (b) Paraphyletic group
Figure 20.10b
(b) Paraphyletic group A B C D
Figure 20.10b Monophyletic, paraphyletic, and polyphyletic groups (part 2: paraphyletic) E
Group II 2 F G 42

43. A polyphyletic grouping consists of various taxa with different ancestors43

44. (c) Polyphyletic group
Figure 20.10c
(c) Polyphyletic group A 1 B
Group III C D
Figure 20.10c Monophyletic, paraphyletic, and polyphyletic groups (part 3: polyphyletic) E 2 F G 44

45. Shared Ancestral and Shared Derived Characters
In comparison with its ancestor, an organism has both shared and different characteristics 45

46. A shared ancestral character is a character that originated in an ancestor of the taxon
A shared derived character is an evolutionary novelty unique to a particular clade
A character can be both ancestral and derived, depending on the context 46

47. Inferring Phylogenies Using Derived Characters
When inferring evolutionary relationships, it is useful to know in which clade a shared derived character first appeared 47

48. TAXA Lancelet (outgroup) (outgroup) Lancelet Lamprey Leopard Bass Frog
Figure 20.11
TAXA
Lancelet
(outgroup)
(outgroup)
Lancelet
Lamprey
Leopard
Bass
Frog
Turtle
Lamprey
Vertebral
column
(backbone) 1 1 1 1 1
Bass
Vertebral
column
Hinged jaws 1 1 1 1
Frog
Four
walking legs
Hinged jaws
CHARACTERS 1 1 1
Turtle
Four walking legs
Amnion 1 1
Figure Constructing a phylogenetic tree
Amnion
Hair 1
Leopard
Hair
(a) Character table
(b) Phylogenetic tree 48

49. TAXA (outgroup) Lancelet Lamprey Leopard Bass Turtle Frog Vertebral
Figure 20.11a
TAXA
(outgroup)
Lancelet
Lamprey
Leopard
Bass
Turtle
Frog
Vertebral
column
(backbone) 1 1 1 1 1
Hinged jaws 1 1 1 1
Four
walking legs
CHARACTERS 1 1 1
Figure 20.11a Constructing a phylogenetic tree (part 1: character table)
Amnion 1 1
Hair 1
(a) Character table 49

50. Lancelet (outgroup) Lamprey Bass Vertebral column Frog Hinged jaws
Figure 20.11b
Lancelet
(outgroup)
Lamprey
Bass
Vertebral
column
Frog
Hinged jaws
Turtle
Four walking legs
Figure 20.11b Constructing a phylogenetic tree (part 2: phylogenetic tree)
Amnion
Leopard
Hair
(b) Phylogenetic tree 50

51. The outgroup is a group that has diverged before the ingroup
An outgroup is a species or group of species that is closely related to the ingroup, the various species being studied
The outgroup is a group that has diverged before the ingroup
Systematists compare each ingroup species with the outgroup to differentiate between shared derived and shared ancestral characteristics 51

52. Characters shared by the outgroup and ingroup are ancestral characters that predate the divergence of both groups from a common ancestor 52

53. Phylogenetic Trees with Proportional Branch Lengths
In some trees, the length of a branch can reflect the number of genetic changes that have taken place in a particular DNA sequence in that lineage 53

54. Drosophila Lancelet Zebrafish Frog Chicken Human Mouse Figure 20.12
Figure Branch lengths can represent genetic change
Mouse 54

55. In other trees, branch length can represent chronological time, and branching points can be determined from the fossil record 55

56. Drosophila Lancelet Zebrafish Frog Chicken Human Mouse 542 251
Figure 20.13
Drosophila
Lancelet
Zebrafish
Frog
Chicken
Human
Figure Branch lengths can indicate time
Mouse
PALEOZOIC
MESOZOIC
CENOZOIC
542
251
65.5 Present
Millions of years ago 56

57. Maximum Parsimony
Systematists can never be sure of finding the best tree in a large data set
They narrow possibilities by applying the principle of maximum parsimony 57

58. Computer programs are used to search for trees that are parsimonious
Maximum parsimony assumes that the tree that requires the fewest evolutionary events (appearances of shared derived characters) is the most likely
Computer programs are used to search for trees that are parsimonious 58

59. Three phylogenetic hypotheses:
Figure 20.14
Technique
1/C I I
III
1/C II
III II
1/C
III II I
1/C
1/C
Species I
Species II
Species III
3/A
2/T
3/A
Three phylogenetic hypotheses: I I
III
2/T
3/A
4/C I I
III II
III II II
III II
4/C
4/C
2/T
III II I
3/A 4/C
2/T 4/C
2/T 3/A
III II I
Site
Figure Research method: applying parsimony to a problem in molecular systematics 1 2 3 4
Results
Species I C T A T I I
III
Species II C T T C II
III II
Species III A G A C
III II I
Ancestral sequence A G T T
6 events
7 events
7 events 59

60. I I III II III II III II I Species I Species II Species III
Figure 20.14a
Technique
Species I
Species II
Species III
Three phylogenetic hypotheses:
Figure 20.14a Research method: applying parsimony to a problem in molecular systematics (part 1: hypothesis) I I
III II
III II
III II I 60

61. Technique Site 1 2 3 4 Species I C T A T Species II C T T C
Figure 20.14b
Technique
Site 1 2 3 4
Species I C T A T
Species II C T T C
Species III A G A C
Figure 20.14b Research method: applying parsimony to a problem in molecular systematics (part 2: table)
Ancestral sequence A G T T 61

62. Technique 1/C I I III 1/C II III II 1/C III II I 1/C 1/C 3/A 2/T 3/A I
Figure 20.14c
Technique
1/C I I
III
1/C II
III II
1/C
III II I
1/C
1/C
3/A
2/T
3/A I I
III
2/T
Figure 20.14c Research method: applying parsimony to a problem in molecular systematics (part 3: comparison)
3/A
4/C II
III II
4/C
4/C
2/T
III II I
3/A 4/C
2/T 4/C
2/T 3/A 62

63. Results I I III II III II III II I 6 events 7 events 7 events
Figure 20.14d
Results I I
III II
III II
III II I
Figure 20.14d Research method: applying parsimony to a problem in molecular systematics (part 4: results)
6 events
7 events
7 events 63

64. Phylogenetic Trees as Hypotheses
The best hypotheses for phylogenetic trees fit the most data: morphological, molecular, and fossil
Phylogenetic hypotheses are modified when new evidence arises 64

65. Phylogenetic bracketing allows us to predict features of ancestors and their extinct descendants based on the features of closely related living descendants
For example, phylogenetic bracketing allows us to infer characteristics of dinosaurs based on shared characters in modern birds and crocodiles 65

66. Lizards and snakes Crocodilians Ornithischian dinosaurs Common
Figure 20.15
Lizards
and snakes
Crocodilians
Ornithischian
dinosaurs
Common
ancestor of
crocodilians,
dinosaurs,
and birds
Saurischian
dinosaurs
Figure A phylogenetic tree of birds and their close relatives
Birds 66

67. The fossil record supports nest building and brooding in dinosaurs
Birds and crocodiles share several features: four-chambered hearts, song, nest building, and brooding
These characteristics likely evolved in a common ancestor and were shared by all of its descendants, including dinosaurs
The fossil record supports nest building and brooding in dinosaurs 67

68. Figure 20.16
Figure A crocodile guards its nest. 68

69. (b) Artist’s reconstruction of the dinosaur’s posture based on
Figure 20.17
Front
limb
Hind
limb
Eggs
Figure Fossil support for a phylogenetic prediction
(b) Artist’s reconstruction of the
dinosaur’s posture based on
the fossil findings
(a) Fossil remains of Oviraptor
and eggs 69

70. (a) Fossil remains of Oviraptor and eggs
Figure 20.17a
Front
limb
Hind
limb
Figure 20.17a Fossil support for a phylogenetic prediction (part 1: fossil)
Eggs
(a) Fossil remains of Oviraptor and eggs 70

71. (b) Artist’s reconstruction of the dinosaur’s posture based on
Figure 20.17b
Figure 20.17b Fossil support for a phylogenetic prediction (part 2: artist’s reconstruction)
(b) Artist’s reconstruction of the
dinosaur’s posture based on
the fossil findings 71

72. Proteobacteria (Mitochondria)* Chlamydias Domain Bacteria Spirochetes
Figure 20.20c
Proteobacteria
(Mitochondria)*
Chlamydias
Spirochetes
Domain Bacteria
Gram-positive
bacteria
Figure 20.20c The three domains of life (part 3: bacteria)
Cyanobacteria
(Chloroplasts)* 72

73. Domains Bacteria and Archaea are single-celled prokaryotes
The three-domain system highlights the importance of single-celled organisms in the history of life
Domains Bacteria and Archaea are single-celled prokaryotes
Only three lineages in the domain Eukarya are dominated by multicellular organisms, kingdoms Plantae, Fungi, and Animalia 73

74. The Important Role of Horizontal Gene Transfer
The tree of life suggests that eukaryotes and archaea are more closely related to each other than to bacteria
The tree of life is based largely on rRNA genes, which have evolved slowly, allowing detection of homologies between distantly related organisms
Other genes indicate different evolutionary relationships 74

75. Horizontal gene transfer complicates efforts to build a tree of life
There have been substantial interchanges of genes between organisms in different domains
Horizontal gene transfer is the movement of genes from one genome to another
Horizontal gene transfer occurs by exchange of transposable elements and plasmids, viral infection, and fusion of organisms
Horizontal gene transfer complicates efforts to build a tree of life 75

76. Horizontal gene transfer may have been common enough that the early history of life is better depicted by a tangled web than a branching tree 76

77. Domain Eukarya Archaea Domain Domain Bacteria Fungi Plantae
Figure 20.21
Fungi
Domain Eukarya
Plantae
Chloroplasts
Methanogens
Archaea
Domain
Ancestral cell
populations
Mitochondria
Thermophiles
Figure A tangled web of life
Cyanobacteria
Proteobacteria
Domain Bacteria 77

78. Domain Eukarya Fungi Plantae Ancestral cell populations Figure 20.21a
Figure 20.21a A tangled web of life (part 1: eukarya) 78

79. Archaea Domain Domain Bacteria Methanogens Thermophiles Ancestral cell
Figure 20.21b
Methanogens
Archaea
Domain
Thermophiles
Ancestral cell
populations
Cyanobacteria
Proteobacteria
Domain Bacteria
Figure 20.21b A tangled web of life (part 2: archaea and bacteria) 79

80. (a) (b) (c) A B A B D C C C B D A A Figure 20.UN01
Figure 20.UN01 Concept check 20.1, p. 385
(a)
(b)
(c) 80

81. Reptiles (including birds) OTHER TETRAPODS Dimetrodon Cynodonts
Figure 20.UN02
Reptiles
(including birds)
OTHER
TETRAPODS
Dimetrodon
Cynodonts
Figure 20.UN02 Concept check 20.3, p. 392
Mammals 81

82. Brown bear Polar bear American black bear Asian black bear Sun bear
Figure 20.UN03
Brown bear 7
Polar bear 4
American black bear 6
Asian black bear 5 3
Sun bear 2
Figure 20.UN03 Skills exercise: interpreting data in a phylogenetic tree
Sloth bear 1
Spectacled bear
Giant panda 82

83. Branch point Taxon A Most recent Taxon B common ancestor Sister taxa
Figure 20.UN04
Branch point
Taxon A
Most recent
common
ancestor
Taxon B
Sister taxa
Taxon C
Taxon D
Taxon E
Figure 20.UN04 Summary of key concepts: evolutionary relationships
Polytomy
Taxon F
Taxon G
Basal taxon 83

84. A A A B B B C C C D D D E E E F F F G G G Monophyletic group
Figure 20.UN05
Monophyletic group
Polyphyletic group A A A B B B C C C D D D E E E
Figure 20.UN05 Summary of key concepts: shared characters F F F G G G
Paraphyletic group 84

85. Salamander Lizard Goat Human Figure 20.UN06
Figure 20.UN06 Test your understanding, question 5
Human 85

86. Figure 20.UN07
Figure 20.UN07 Test your understanding, question 8 86