1. Chapter 25 Essential Questions
LO 1.13 The student is able to construct and/or justify mathematical
models, diagrams or simulations that represent processes of
biological evolution.
LO 1.17 The student is able to pose scientific questions about a group of
organisms whose relatedness is described by a phylogenetic tree
or cladogram in order to (1) identify shared characteristics,
(2) make inferences about the evolutionary history of the group,
and (3) identify character data that could extend or improve the
phylogenetic tree.
LO 1.18 The student is able to evaluate evidence provided by a data set
in conjunction with a phylogenetic tree or a simple cladogram to
determine evolutionary history and speciation.
LO 1.19 The student is able create a phylogenetic tree or simple
cladogram that correctly represents evolutionary history and
speciation from a provided data set.
LO 1.26 The student is able to evaluate given data sets that illustrate
evolution as an ongoing process.

2. Chapter 25: Phylogeny & Systematics
What is phylogeny?
Evolutionary history of a species
How can we trace phylogeny?
Relative dating
Based on layer fossil is found in
Older or younger
Absolute dating – p 517
Radiometric dating – C14, U238
Years ago alive
Example:
How long ago was fossilized organism alive?
Given: 1/16 isotope remaining & isotope has t½ = 4000 yrs
Answer
1/16 = 4 half lives
4 X 4000 yrs = 16,000 yrs ago it was alive

3. Figure 25.4 A gallery of fossil types
(a) Dinosaur bones being excavated from sandstone
(g) Tusks of a 23,000-year-old mammoth, frozen whole in Siberian ice
(e) Boy standing in a 150-million-year-old dinosaur track in Colorado
(d) Casts of ammonites, about 375 million years old
(f) Insects preserved whole in amber
(b) Petrified tree in Arizona, about 190 million years old
(c) Leaf fossil, about 40 million years old

4. Students
Place lab notebooks on shelf
LL mid-point check – Monday
How many watched the H-W video from Bozeman Science?
Phones in bin…muted or off….please & thank you!!
Any LL questions now? 

5. Chapter 25: Phylogeny & Systematics
What is phylogeny?
How can we trace phylogeny?
Why aren’t there more fossils for “missing links” to extant organisms?
Conditions must be perfect for fossilization & discovery
May be present but not found
What is the difference between convergent & divergent evolution?
Convergent
Species from different evolutionary branches develop structures that
resemble one another…no common ancestor
Shows analogy between species…..not homology from a
common ancestor
Divergent – gradual changes over time
5. What is taxonomy?
Identification & classification of species
D K P C O F G S

6. Figure 25.8 Hierarchical classification
Panthera
pardus
Felidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

7. Chapter 25: Phylogeny & Systematics
What is phylogeny?
How can we trace phylogeny?
Why aren’t there more fossils for “missing links” to extant organisms?
Conditions must be perfect for fossilization & discovery
May be present but not found
What is the difference between convergent & divergent evolution?
Convergent
Species from different evolutionary branches develop structures that
resemble one another
Shows analogy between species…..not homology from a
common ancestor
Divergent – gradual changes over time
5. What is taxonomy?
Identification & classification of species
D K P C O F G S
6. What is a cladogram?
Diagram that shows shared characteristics

8. Figure 25.11 Constructing a cladogram

9. Chapter 25: Phylogeny & Systematics
What is phylogeny?
How can we trace phylogeny?
Why aren’t there more fossils for “missing links” to extant organisms?
Conditions must be perfect for fossilization & discovery
May be present but not found
What is the difference between convergent & divergent evolution?
Convergent
Species from different evolutionary branches develop structures that
resemble one another
Shows analogy between species…..not homology from a
common ancestor
Divergent – gradual changes over time
5. What is taxonomy?
Identification & classification of species
D K P C O F G S
6. What is a cladogram?
Diagram that shows shared characteristics
Groups can either be monophyletic, paraphyletic or polyphyletic

10. Monophyletic – one group coming from a single common ancestor
Paraphyletic – a grouping with one but not all ancestors derived from it
Polyphyletic – a grouping of several species that lack a common ancestor

11. Chapter 25: Phylogeny & Systematics
What is phylogeny?
How can we trace phylogeny?
Why aren’t there more fossils for “missing links” to extant organisms?
Conditions must be perfect for fossilization & discovery
May be present but not found
What is the difference between convergent & divergent evolution?
What is taxonomy?
What is a cladogram?
How can molecular clocks help to track evolutionary time?
Assumes that some genes & parts of the genome appear to evolve
at a constant rate
We can then compare genomic changes to known evolutionary
branch points in the fossil record
Using a molecular clock, researchers concluded that HIV-M first infected
humans in the 1930s
8. How have all organisms descended from a common ancestor on
the universal tree of life?

12. Figure 25.18 The universal tree of life
Bacteria
Eukarya
Archaea
4 Symbiosis of chloroplast ancestor with ancestor of green plants
3 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes
2 Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells
1 Last common ancestor of all living things 4 3 2 1
Billion years ago
Origin of life
Many phylogentic relationships have been shown through molecular biology
- DNA sequencing
- protein sequencing