1. Chapter 25 Phylogeny and Systematics

2. Macroevolution Attempts to explain how major adaptive characteristics came into existence These characteristics would be the basis for creating new taxa above the species level – Individual unit of classification system Ex: Kingdom

3. Phylogeny The evolutionary history of a species or group of related species Constructed through fossils, DNA/RNA/ protein analysis

4. Systematics Study of biodiversity in an evolutionary context Uses taxonomy to trace phylogeny Classifies organisms based on evolutionary history

5. Fossil Formation Fossils are formed in sedimentary rock Organisms die, then sediments are deposited on top of them Older fossils on bottom of strata; newer ones in top strata

6. Incomplete Record Organisms don’t always die in locations favoring fossil formation Lots of organisms don’t make fossils Some fossils may never be discovered due to location

7. Mass Extinctions Mass extinctions punctuated by major geological and climatic events – Permian – Pangaea – Cretaceous

8. Systematics: Taxonomy Modern system of taxonomy invented by Linnaeus Sought to give binomial names to all organisms: Genus species naming convention Example: Homo sapiens

9. Hierarchy of Classification Groups organisms from most broad to most specific categories

10. Example

11. Cladistics and Phylogeny Cladistics: study of relationships among organisms shown by common characteristics not found in ancestral group Cladogram: diagram showing relationships among organisms

12. Constructing a Cladogram: Step 1 Sort homology from analogy: – Homologous structures – Analogous structures: do not have common ancestry; different structure, same function

13. Constructing a Cladogram: Step 2 Identify shared primitive characters: – Not limited to group being studied (e.g. backbone) Identify shared derived characters: – Characteristics unique to clade (hair in mammals)

14. Constructing a Cladogram: Step 3 Outgroup comparison – The ingroup is what’s being studied – The outgroup is what you compare ingroup to Identify characteristics to study Make a data matrix Make the cladogram

15. Cladogram

16. DNA Sequences Genome sequencing allows us to study DNA sequences of organisms to observe change over time Sequence alignments generated with computers

17. Amino Acid Sequences Similarities in DNA sequences lead to similarities in AA sequences as well Gaps are present due to mutations

18. Molecular Clocks Based on observation that some genomic regions evolve at constant rates DNA or proteins can be compared and the number of sequence differences is proportional to time passed since branching occurred

19. Example of Molecular Clock: Cytochrome C