1. Phylogeny and Systematics
Chapter 26: (Making “Trees of Life”)

2. Macroevolution
studies focus on change that occurs at or above the level of species
The origin of taxonomic groups higher than species level
How does this occur?
Evolution of new traits (novelties)
mass extinctions
Open adaptive zones (divergent evolution)

3. Currently, scientists use
Morphological, biochemical, and molecular comparisons to infer evolutionary relationships
Obtained through fossil studies, DNA technology and current organisms

4. Phylogeny What is phylogeny? The evolutionary history of a group
Systematics attempts to reconstruct phylogeny, by analyzing evolutionary relatedness.
Use morphological and biochemical similarities
Molecular systematics uses DNA, RNA and proteins to infer evolutionary relatedness.
Different tools are used to reconstruct phylogenies called phylogentic trees.

5. Molecular systematics

6. Systematics
Uses evidence from fossil record and existing organisms to reconstruct phylogeny (Linneaus)
Binomial nomenclature Genus species keeps identity of organism universal
Other taxa used to classify
Domain, Kingdom, Phylum, Class, Order, Family, Genus, species

7. Taxonomy Linnaeus ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences

8. Linking Classification and Phylogeny
Systematists depict evolutionary relationships In branching phylogenetic trees
Panthera pardus (leopard)
Mephitis mephitis (striped skunk)
Lutra lutra (European otter)
Canis familiaris (domestic dog)
Canis lupus (wolf)
Panthera
Mephitis
Lutra
Canis
Felidae
Mustelidae
Canidae
Carnivora
Order
Family
Genus
Species
Figure 25.9

9. Each branch point Represents the divergence of two species Leopard
Domestic cat
Common ancestor

10. “Deeper” branch points
Represent progressively greater amounts of divergence
Leopard
Domestic cat
Common ancestor
Wolf

11. Cladistics Cladogram is a tree with two way branch points
Each branch point represents divergence from common ancestor
Each branch is called a clade
Clades
Can be nested within larger clades, but not all groupings or organisms qualify as clades
3 types of groupings
Monophyletic
Polyphyletic
Paraphyletic

12. Different Types of Clades
Monophyletic = single ancestor gave rise to all species in the taxon; ONLY valid clade
Polyphyletic = includes numerous types of organisms that lack a common ancestor; not a valid clade
Paraphyletic = a grouping that consists of an ancestral species and some, but not all, of the descendants; not a valid clade

13. Clades Grouping 1 Grouping 2 Grouping 3 Monophyletic Paraphyletic
Polyphyletic

14. Let’s practice…

16. Making “Trees”: Morphological & molecular homologies
similarities based on shared ancestries
bone structure
DNA sequences
beware of analogous structures
convergent evolution

17. Not all Similarities Represent Common Ancestry
Homologous structures indicate shared common ancestry
Homologous structures are therefore evidence of divergent evolution
Analogous structures are similar in function but not in evolutionary history
Analogous structures are evidence of convergent evolution
It is not always easy to sort homologous from analogous structures

18. RECALL…
Convergent evolution occurs when similar environmental pressures and natural selection
Produce similar (analogous) adaptations in organisms from different evolutionary lineages
Marsupial
Eutherian
(placental)

19. Making Evolutionary Life Trees: Illustrating Phylogeny
1. Cladistics =
sorts homologous from analogous structures
sorts primitive and shared derived characteristics
Makes cladograms

20. The Universal Tree of Life
The tree of life is divided into three great clades called domains:
Bacteria, Archaea, and Eukarya
Bacteria
Eukarya
Archaea
4 Symbiosis of chloroplast ancestor with ancestor of green plants 1
3 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes 4
Billion years ago 3 2
2 Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells 2 3
1 Last common ancestor of all living things 1
Origin of life 4
Figure 25.18

21. A shared primitive character
a homologous structure that is shared by all groups we are trying to define
A shared derived character
A new evolutionary trait unique to a particular clade(s)
Making Cladograms Activity Time

23. What is the shared primitive characteristic? Notochord
A Cladogram
What is the shared primitive characteristic? Notochord

25. Phylograms In a phylogram
Drosophila
Lancelet
Amphibian
Fish
Bird
Human
Rat
Mouse
Cenozoic
Mesozoic
Paleozoic
Proterozoic
542
251
65.5
Millions of
years ago
In a phylogram
The length of a branch in a cladogram reflects the number of genetic changes that have taken place in a particular DNA or RNA sequence in that lineage
Involves timing cladograms do NOT!