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

6. REMEMBER!!
Dear King Philip Came Over For Good Spaghetti
Dominant Kings Played Canucks On Friday, Gretzky Scored!

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

8. Terminology
Branch Point- represents the divergence of 2 evolutionary lines
Sister taxa- groups of organisms that share an immediate common ancestor (closest relative)
Rooted- a branch point within the tree represents the most recent common ancestor of all taxa in tree
Extant- still living
Basal taxon- lineage that diverges early in history and lies on branch near common ancestor (G)
Polytomy- branch point where more than 2 descendant groups emerged

9. 3 points about Phylogenetic Trees
1) Intended to show patterns of descent not phenotypic similarities
Ex) Crocodiles most closely related to birds than lizards but look more like lizards

10. 3 points about Phylogenetic Trees
2) Sequence of branching does not always indicate absolute age of species 3) Do not assume that a taxon on a phylogenetic tree evolved from the taxon next to it

11. Cladogram: diagram that depicts patterns of shared characteristics among taxa
Clade = group of species that includes an ancestral species + all descendents
Can be nested within larger clades, but not all groupings or organisms qualify as clades
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

12. Taxon is equivalent to a clade if it is monophyletic
Consists of an ancestral species and ALL its descendants

13. A valid clade is monophyletic
Signifying that it consists of the ancestor species and all its descendants
(a) Monophyletic. In this tree, grouping 1, consisting of the seven species B–H, is a monophyletic group, or clade. A mono- phyletic group is made up of an ancestral species (species B in this case) and all of its descendant species. Only monophyletic groups qualify as legitimate taxa derived from cladistics.
Grouping 1 D C E G F B A J I K H
Figure 25.10a

14. Paraphyletic Group
Consists of an ancestral species and some, but not all, of its descendants

15. A paraphyletic clade
Is a grouping that consists of an ancestral species and some, but not all, of the descendants
(b) Paraphyletic. Grouping 2 does not meet the cladistic criterion: It is paraphyletic, which means that it consists of an ancestor (A in this case) and some, but not all, of that ancestor’s descendants. (Grouping 2 includes the descendants I, J, and K, but excludes B–H, which also descended from A.) D C E B G H F J I K A
Grouping 2
Figure 25.10b

16. Polyphyletic Group
Includes distantly related species but does not include their most recent common ancestor

17. A polyphyletic grouping
Includes numerous types of organisms that lack a common ancestor
Grouping 3
(c) Polyphyletic. Grouping 3 also fails the cladistic test. It is polyphyletic, which means that it lacks the common ancestor of (A) the species in the group. Further- more, a valid taxon that includes the extant species G, H, J, and K would necessarily also contain D and E, which are also descended from A. D C B E G F H A J I K
Figure 25.10c

18. Monophyletic, paraphyletic, and polyphyletic groups

19. Constructing a phylogenetic tree
A “0” indicates a character is absent; a “1” indicates that a character is present.

20. Branch lengths can represent genetic change

21. Branch lengths can indicate time

22. 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.

23. Answer:

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

25. Principle of maximum parsimony: use simplest explanation (fewest DNA changes) for tree – “keep it simple” Occam's razor
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

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

27. 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