1. Geologic Time and Phylogeny (Chapter 26)
Evolutionary history...

2. Phylogeny and Systematics
Phylogeny: The evolutionary history of a species or group of related species
Like an evolution family tree:
Systematics: the study of biological diversity in an evolutionary context
grouping organisms and seeing how organisms are related due to evolution

3. How do scientists create a phylogeny?
Fossils: the preserved remnants or impressions left by organisms that lived in the past.

5. How do scientists know the age of a fossil?
Relative Dating
New layers form on top of old ones
When a dead organism is trapped in sediment, this fossil is frozen in time relative to other strata (layers) in a local sample

6. Absolute Dating
Radiometric dating is the method used most often to determine absolute ages for fossils.
organisms accumulate radioactive isotopes when they are alive, but concentrations of these isotopes decline after they die.
These isotopes undergo radioactive decay…
one element is transformed to another element.
An isotope’s half-life, the
time it takes for 50% of the
original sample to decay,
unaffected by temperature,
pressure, or other variables.

7. Carbon-14
The radioactive isotope, carbon-14, is present in living organisms.
Organism dies: carbon-14 decays to nitrogen-14
The half-life of carbon-14 is 5,730 years
It is possible to determine the age of a sample by examining how much C14 has decayed.

8. Uranium- 238
Elements with longer half-lives are used to date older fossils.
While uranium-238 (half life of 4.5 billion years) is not present in living organisms to any significant level, it is present in volcanic rock.
If a fossil is found sandwiched between two layers of volcanic rock, we can deduce that the organism lived in the period between the dates in which each layer of volcanic rock formed.

9. Relative vs. Absolute Dating

10. Geologic Time Scale
Geologists have established a geologic time scale with a consistent sequence of historical periods.
These periods are grouped into four eras: the Precambrian, Paleozoic, Mesozoic, and Cenozoic eras.
Boundaries between geologic eras and periods correspond to times of great change, especially mass extinctions, not to periods of similar length.

12. Mass Extinctions

13. Mass Extinctions

14. Plate Tectonics

15. Plate Tectonics

16. Phylogeny and Systematics
Organizing evolution!

17. Intro The goal - to reconstruct the history of life on earth.
The method – Systematics is the study of biological diversity in an evolutionary context.
The result: The development of phylogeny, the evolutionary history of a species or group of related species.

18. Classification
Taxonomy: Naming and classification of species and groups of species
Scientists use hierarchical classification of species into broader and broader groups

19. Example How would you classify a Toyota 4Runner? Transportation Car
SUV
Toyota 4Runner

20. Try this!
Organize the taxa. Start with the smallest group at the bottom and work your way up to largest group at the top.
Next match the scientific names for the cheetah with the correct taxa.

22. Phylogeny and Cladograms
Phylogeny: The evolutionary history a species or group of species
Cladogram: phylogenetic diagram based on cladistics
Each branch point represents the divergence of two species from a common ancestor

23. Connection between classification and phylogeny…

25. Now try this!
Imagine you are a scientist studying insects in the rainforest of Bolivia. You’ve found six insects that look like they are related. Based on shared derived characteristics construct a cladogram and character table.