1. Phylogeny and the Tree of Life
Chapter 26
Phylogeny and the Tree of Life

2. What you need to know:
The taxonomic categories and how they indicate relatedness.
How systematics is used to develop phylogenetic trees.
The three domains of life including their similarities and their differences.

3. (evolutionary history)
Systematics: classifying organisms and determining their evolutionary relationships
Taxonomy
(classification)
Systematics
Phylogenetics
(evolutionary history)

4. Tools used to determine evolutionary relationships: Fossils
Morphology (homologous structures)
Molecular evidence (DNA, amino acids)
Who is more closely related?
Animals and fungi are more closely related than either is to plants.

5. Fossil record Sedimentary rock are richest source of fossils
Sedimentary rock are richest source of fossils
fossil record is a substantial chronicle of evolutionary history
Can determine time and reveal extinct species
history of life on Earth is punctuated by mass extinctions
Weakness = not all species leave fossils
Fossil record is incomplete
5000 year old ice mummy found on an Alpine ridge dividing Austria from Italy at 10,500 feet above sea level.

6. Morphological & molecular homologies
Morphological & molecular homologies
similarities based on shared ancestries
bone structure
Homologous structures indicate common ancestor
Weakness= analogous structures
convergent evolution = not related
marsupial mole
placental mole

7. Evaluating molecular homologies
Aligning DNA sequences
more bases in common = more closely related
Allows study of evolution between closely related species
beware of molecular homologies

8. Evaluating molecular homologies
Weakness
Little to no data for extinct species
Variation within species blurs differences between species
How different to be a new species?

9. Taxonomy: science of classifying and naming organisms
Binomial nomenclature (Genus species)
Naming system developed by Carolus Linnaeus.

10. REMEMBER!!
Dear King Philip Came Over For Good Spaghetti
Dear King Philip Crossed Over Five Great Seas
Dear King Philip Came Over From Germany Stoned
Your own???

11. Phylogenetic Tree
Branching diagram that shows evolutionary history of a group of organisms

13. Cladogram: diagram that depicts patterns of shared characteristics among taxa
Clade = group of species that includes an ancestral species + all descendents
Shared derived characteristics are used to construct cladograms
Turtle
Leopard
Hair
Amniotic egg
Four walking legs
Hinged jaws
Vertebral column
Salamander
Tuna
Lamprey
Lancelet (outgroup)
Cladogram

14. Monophyletic, paraphyletic, and polyphyletic groups

15. Constructing a phylogenetic tree
A 0 indicates a character is absent; a 1 indicates that a character is present.

16. Branch lengths can represent genetic change

17. Branch lengths can indicate time

18. Draw a phylogenetic tree based on the data below
Draw a phylogenetic tree based on the data below. Draw hatch marks on the tree to indicate the origin(s) of each of the 6 characters.

19. Answer:

20. Various tree layouts
Circular (rooted) tree
Unrooted tree
Rooted tree

21. Principle of maximum parsimony: use simplest explanation (fewest DNA changes) for tree – “keep it simple”
Molecular clocks: some regions of DNA appear to evolve at constant rates
Estimate date of past evolutionary events
Eg. Origin of HIV infection in humans= 1930’s

22. Tree of Life
3 Domains: Bacteria, Archaea, Eukarya

23. Identification of species
SYSTEMATICS
focuses on
phylogeny
Biological diversity
taxonomy
cladistics
classification
Identification of species D K P C O F G S
Homologous
similarities
fossils
binomial
molecular
Genus, species
morphology