1. Warm-Up
Contrast adaptive radiation vs. convergent evolution? Give an example of each.
What is the correct sequence from the most comprehensive to least comprehensive taxon?
In a population of 500 rabbits, 320 are homozygous dominant for brown coat color (BB), 160 are heterozygous (Bb), and 20 are homozygous white (bb).
What are the frequencies of the alleles (B and b)?
What are the frequencies of the different genotypes (BB, Bb, and bb)?

2. Who is most closely related to Animal A?
Warm-Up
Arrange these animals in a tree-like diagram that shows relateness based on this information:
Animal A: 4 chambered-heart (2 atria, 2 ventricles)
Animal B: 3-chambered heart (2 atria, 1 ventricle)
Animal C: muscular tube that pumps blood
Animal D: 2-chambered heart (1 atrium, 1 ventricle)
Animal E: 3-chambered heart (2 atria, 1 partially- divided ventricle)
Who is most closely related to Animal A?

3. Evolution of Heart Chambers in Animals
Fish:
2-chambered heart
Amphibians & Reptiles:
3-chambered heart
Birds & Mammals:
4-chambered heart

4. Chapter 20
Phylogeny

5. (evolutionary history)
Systematics: classifying organisms and determining their evolutionary relationships
Taxonomy
(classification)
Systematics
Phylogenetics
(evolutionary history)

6. Tools used to determine evolutionary relationships: Fossils
Morphology (homologous structures)
Molecular evidence (DNA, amino acids)
Who is more closely related?
Animals and fungi are more closely related than either is to plants.

7. What kind of organism is this?
Legless conditions evolved separately  analogous structures evolved by convergent evolution
What kind of organism is this?

8. Taxonomy: classifying and naming organisms
Ordered division of organisms based on similar/different characteristics Dear King Philip Came Over For Good Spaghetti Each category at any level is called a taxon.

9. Binomial nomenclature (Genus species)
Naming system developed by Carolus Linnaeus

10. Phylogenetic Tree
Branching diagram that shows evolutionary history of a group of organisms

12. Branch lengths can represent genetic change

13. Branch lengths can indicate time

14. Various tree layouts
Circular (rooted) tree
Unrooted tree
Rooted tree

15. Constructing Phylogenetic Trees
Divergent vs. Convergent Evolution
Sorting homology from analogy

17. Cladogram: diagram that depicts patterns of shared characteristics among groups
Clade = group of species that includes an ancestral species + all descendents
Shared derived characteristics (evolutionary novelties) are used to construct cladograms
Turtle
Leopard
Hair
Amniotic egg
Four walking legs
Hinged jaws
Vertebral column
Salamander
Tuna
Lamprey
Lancelet (outgroup)
Cladogram
Shared ancestral characteristic (of all vertebrates) = vertebral column
Shared derived characteristic of mammals = hair

18. Taxa
Lungs
tail
jaws
nostrils
feathers
Duck +
owl
Parrot
Snake -
dog

20. Constructing a phylogenetic tree
A 0 indicates a character is absent; a 1 indicates that a character is present.

21. Draw a phylogenetic tree based on the data below
Draw a phylogenetic tree based on the data below. Draw hatch marks on the tree to indicate the origin(s) of each of the 6 characters.

22. Answer:

23. Principle of maximum parsimony: use simplest explanation (fewest DNA changes) to construct phylogenetic tree – “keep it simple”
The first tree is the most parsimonious  fewest changes in bases

24. Molecular clock for mammals
Molecular clocks: measure evolutionary change based on regions of genome that appear to evolve at constant rates
Estimate date of past evolutionary events
Eg. Origin of HIV infection in humans= 1930’s
Molecular clock for mammals
Origin of HIV-1 M

25. 3 Domains: Bacteria, Archaea, Eukarya
Tree of Life
3 Domains: Bacteria, Archaea, Eukarya
Based on sequence data for rRNA and other genes

26. Common Ancestry of All Life Forms
Elements conserved across all 3 domains:
DNA and RNA are carriers of genetic info
Universal genetic code (codons  amino acids)
Conserved metabolic pathways

27. Conserved elements in Eukaryotes:
Cytoskeleton
Membrane-bound organelles
Linear chromosomes
Endomembrane systems (including nuclear envelope)

28. Horizontal Gene Transfer
Movement of genes between different domains
Exchange of transposable elements, plasmids, viral infections, fusion of organisms
Trees are complex!
Phylogenetic trees are hypotheses subject to change based on available data