1. Chapter 26 – Phylogeny & the Tree of Life

2. 26.1
Phylogeny
Evolutionary history of a species or a group of related species
Made by using evidence from systematics
Focuses on classifying organisms & relationships
Uses fossils, morphology, genes, & molecular evidence

3. Taxonomy Ordered division of organisms into categories
Based on a set of characteristics used to assess similarities & differences

4. Binomial Nomenclature
2 part naming system that consists of the GENUS & the SPECIES
Example: Canis familiaris (common dog)
Devoloped by Linnaeus

5. Hierarchical classification of organisms:
DOMAIN
KINGDOM
PHLUM
CLASS
ORDER
FAMILY
GENUS
SPECIES
The level of relatedness increases as you move down the list

7. Phylogenetic trees
Used to depict hypotheses about evolutionary relationships
The branches of the trees reflect the hierarchical classifications of groups nested within more inclusive groups

9. 26.2 Phylogenies are inferred from morphological & molecular data
1) Homologous structures
Similarities due to shared ancestry (whale’s flipper)
2) Convergent evolution
When 2 organisms developed similarities as they adapted to similar environmental challenges
Note due to common ancestor
Streamlined bodies of a tuna & dolphin

10. 3) Analogous structures
Structures from convergent evolution
Wings of butterfly & bat
4) Molecular systematics
Uses DNA to determine evolutionary relationships
The more alike the DNA sequences of 2 organisms, the more closely related they are

11. 26.3 Building of a phylogenetic tree
A cladogram depicts patterns of shared characteristics among taxa & forms the basis of a PT
A clade (within a tree) is defined as a group of species that includes an ancestral species & all of its descendants

12. A valid clade is monophyletic, signifying that it consists of the ancestor species and all its descendants

13. A paraphyletic grouping consists of an ancestral species and some, but not all, of the descendants

14. A polyphyletic grouping consists of various species that lack a common ancestor

15. 26.4
The rate of evolution in DNA sequences varies from one part of the genome to another
By comparing the different sequences, one can investigate relationships between groups of organisms that diverged a long time ago

16. DNA that codes for mitochondrial DNA evolves rapidly
Used to explore recent events
DNA that codes for ribosomal RNA changes relatively slowly
Useful for investigating relationships between taxa that diverged hundreds of millions of years ago

17. Molecular clocks
Methods used to measure the absolute time of evolutionary change
Based on the observation that some genes appear to evolve at constant rates

19. Difficulties of molecular clocks
The molecular clock does not run as smoothly as neutral theory predicts
Irregularities result from natural selection in which some DNA changes are favored over others
Estimates of evolutionary divergences older than the fossil record have a high degree of uncertainty
The use of multiple genes may improve estimates

20. 26.6
New information continues to revise our understanding of the tree of life
Early taxonomists classified all species as either plants or animals
Later, five kingdoms were recognized: Monera (prokaryotes), Protista, Plantae, Fungi, and Animalia
More recently, the three-domain system has been adopted: Bacteria, Archaea, and Eukarya
The three-domain system is supported by data from many sequenced genomes

25. Bacteria & Archaea Eukarya Contain prokaryotic organisms
Contain eukaryotic organisms

26. Characteristic Bacteria Achaea Eukarya
Nuclear Envelope No
Yes
Membrane-bound Organelles
Introns
Histone proteins used with DNA
Circular chromosome