1. Chapter 26 Phylogeny and the Tree of Life

2. Objective
SWBAT explain and demonstrate that organisms share many conserved core processes and features that evolved and are widely distributed among organisms today.

3. Agenda Chapter 25 Quiz Chapter 26 notes: sections 26.1, 26.2, and 26.3
Guided practice with phylogeny
Homework:
a) Phylogeny Worksheet. Due Monday, September 22
b) Read all of Chapter 26 this weekend for Monday.

4. Phylogeny and the Tree of Life Chapter 26

5. The Origin of Species
As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever-branching and beautiful ramifications. ~ Charles Darwin

6. Evolution as a branching, tree-like process
Darwin’s Tree of Life
Evolution as a branching, tree-like process

7. A phylogenetic tree of the bacterial domain.
A phylogenetic tree represents a hypothesis of the order in which evolutionary events are assumed to have occurred.

8. Phylogenetics
Phylogenetics is the study of evolutionary relatedness among various groups of organisms, which is discovered through molecular sequencing and morphological data.
Tucuxi

9. What do phylogenetic trees represent?
Madison DR (2012) Phylogeny of Bembidion and related ground beetles. Molecular Phylogenetic and Evolution 64:

10. Going back in time…

11. Present
Past

12. on connecting branches
2 leaves…
on connecting branches
How can we hypothesize that this speciation event occurred ~ 1.5 million years ago?

13. The key is in the DNA
Species vary in their gene pools (the alleles for all traits)
The gene pool of a population changes over time
natural selection
genetic drift
genetic recombination
mutation

14. Mutation
Change in nucleotide sequence of an organism’s DNA

15. Molecular clock
The mutation rates of particular genes are relatively constant, thus the rate of mutations can be used as a molecular clock
If mutation rates are constant, then we can use such genes to extrapolate when speciation events took place
Example: The gene that codes for hemoglobin experiences 0.56 changes per base pair per billion years

19. The cytochrome c gene reflects a pattern of differences in DNA sequences due to mutations.
The changes accumulate at a constant rate, and can be used as a molecular clock to help date evolutionary divergences.

21. Order Family Genus Species Panthera pardus (leopard) Felidae Panthera
Figure 26.4
Order
Family
Genus
Species
Panthera
pardus
(leopard)
Felidae
Panthera
Taxidea
taxus
(American
badger)
Taxidea
Carnivora
Mustelidae
Lutra lutra
(European
otter)
Lutra
Figure 26.4 The connection between classification and phylogeny.
Canis
latrans
(coyote)
Canidae
Canis
Canis
lupus
(gray wolf)

22. (a) Monophyletic group (clade) (b) Paraphyletic group
Figure 26.10
(a) Monophyletic group (clade)
(b) Paraphyletic group
(c) Polyphyletic group A A A B
Group  B B
Group  C C C D D D E E
Group  E
Figure Monophyletic, paraphyletic, and polyphyletic groups. F F F G G G

23. on connecting branches
2 leaves…
on connecting branches
How can we hypothesize that this speciation event occurred ~ 1.5 million years ago?

24. Answer: Use the amount of variability between DNA sequences to estimate the time of speciation events

25. The evolution of HIV

26. 1884 – 1924 1966 2010 HIV jumped from chimps to humans
Africa  Haiti  U.S. (Robert R., first HIV/AIDS death in U.S., 1969)
2010
Evidence that a newer strain of HIV jumped to humans from gorillas

27. We can also use morphological differences to deconstruct evolutionary relationships
Derived
Ancestral

28. Hair is a shared derived trait (synapomorphy) of mammals
We can also use morphological differences to deconstruct evolutionary relationships
Derived
Ancestral
Hair is a shared derived trait (synapomorphy) of mammals

29. Parsimony: evolution takes the easier path

30. Parsimony: evolution takes the easier path

31. Guided Practice on Parsimony: which one is the most parsimonious tree?

32. Parsimony: evolution takes the easier path

33. Guided Practice: What is the difference between these trees?

34. Guided Practice: What is the difference between these trees?
They are all the same. B and C are sister species. In addition, A, B, and C share a common ancestor in all trees.

35. Guided Practice: What is the difference between these trees?

36. What is the difference between these trees?
They are all the same. Humans, chimps, and common ancestor 1 are monophyletic. Gorillas are an outgroup to humans and chimps. Orangutans are also an outgroup to common ancestor 2 and its descendants.

37. Using phylogenetics to solve a crime

38. Summary
Phylogeny is the evolutionary history of a species or group of related species
The discipline of systematics classifies organisms and determines their evolutionary relationships
Systematists use fossil, molecular, and genetic data to infer evolutionary relationships

39. 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

40. Species: Panthera pardus Genus: Panthera Family: Felidae Order:
Figure 26.3
Species:
Panthera pardus
Genus:
Panthera
Family:
Felidae
Order:
Carnivora
Class:
Mammalia
Figure 26.3 Linnaean classification.
Phylum:
Chordata
Kingdom:
Animalia
Domain:
Bacteria
Domain:
Archaea
Domain:
Eukarya