1. Tree of Life
Chapter 26

2. Where Are We Going? Taxonomy Phylogeny Application
Scientific discipline of classifying and naming organisms
Phylogeny
Interpreting diagrams of evolutionary history
Application
What evolutionary history says about biological diversity

3. Binomial Nomenclature
Common names for casual usage, but not accurate
What animals come to mind you when hear the word ‘fish’?
Different words depending on language
Biologist use Latin scientific names
Carolus Linnaeus
2 part system: genus and specific epithet
Homo sapiens or Panthera pardus
Jellyfish (cnidarian), crawfish (crustacean), silverfish (insecta), seahorses and salmon (bony fish)
Pez (sp), poisson (fr), fisch (ger),

4. Hierarchical (Linnaean) Classification
Linnaeus grouped named animals into categories
genus Panthera: leopard (P. pardus), lion (P. leo), tiger (P.tigris), & jaguar (P. onca)
Based on morphological similarities
Used by taxonomists
Taxon is any level of the hierarchy
Review: How can you remember the hierarchical order of taxons?
Doesn’t always reflect evolutionary history

5. Phylogenetic Trees
Diagrams hypotheses of evolutionary history of organisms
Degree of relatedness to ancestors
Used by systematists
Can reclassify if mistake found
Only implies pattern of descent, not time or age
Branch means common ancestor, not taxon from taxon

6. Reading Phylogenetic Trees
Which of the trees
below depicts a
different evolutionary
history from the other
two?
Series of branch points
Root is last common
ancestor of tree
Sister taxa share an
immediate ancestor

7. Homology vs Analogy Homologies are similarities due to shared ancestry
Used to construct phylogenies
Analogies are similarity due to convergent evolution
What is convergent evolution?
‘Moles’: marsupial vs eutherian; similar lives
Wings: bats vs. insects vs. birds; relation to cats
More points of resemblance make more likely ancestor was shared
Applies to morphological and molecular
similarities

8. Constructing Phylogenetic Trees
Must first separate homologous from analogous
Systematists then infer phylogeny using cladistics
Using common ancestry to classify organisms
Create clades or groups containing an ancestral species and all descendants

9. Clades vs. Taxons Similar to taxons because both are nested groups
Equivalent only if it is monophyletic, containing ancestor and ALL descendants
Paraphyletic contains ancestor and SOME descendants
Polyphyletic contain taxa with different ancestors

10. Shared … Characteristics
Ancestral originates in an ancestor of the taxon
Backbones are an example for mammals, why?
Derived is a novelty unique to a clade
Hair is an example for mammals, why?
Ancestral can qualify as derived at deeper branches
What branch point allows backbones to be shared derived characteristics?

11. Constructing Phylogenies
Use the 1st appearance of each shared derived characteristic
Determine the outgroup and ingroup
Determined from morphology, paleontology, embryonic development, or genes
Compare members of the ingroup to each other and to the outgroup

12. The Genome’s Role in Phylogeny
Nucleic acids and other molecules are also used to determine and test hypotheses about evolutionary relationships
Important for organisms that are unlikely to have morphological similarities or organisms without fossil records
Fungi, plants, and animals
Prokaryotes and other microorganisms
Determine relationships at all levels of the Tree of Life
Rates of gene evolution varies
rRNA is slow = good for relationships that diverged 100’s of millions of years ago
mtDNA is rapid = good for recent evolution

13. Evolving Genomes Orthologous genes Paralogous genes
Homologous genes in different species through speciation
Can diverge only after speciation
E.g cytochrome C (ETC protein)
Paralogous genes
From gene duplication = multiple copies in the same genome
Can diverge within a species
E.g 1000’s of olfactory receptors
Humans and mice 99% orthologous; and yeast 50%

14. The Changing Tree of Life
Initially 2 Kingdoms
Plants: bacteria (cell wall), chloroplast organims, fungi (sessile)
Animals: protozoans (movement and eat)
5 Kingdoms
Monera: prokaryotes
Protista: unicellular organisms
Plantae, Fungi, and Animalia: eukaryotes
Recently 3 Domains
Molecular evidence that prokaryotes as different from each other as eukaryotes
Bacteria: most prokaryotes, close to chloroplasts and mitochondria
Archaea: diverse prokaryotes living in extreme environments
Eukarya: cells with true nuclei

15. Domain Systems 1 example of Life’s connections
Most of living organisms are single-celled
Red lines are multicellular
Monera gone because it contains 2 domains
Protista disappearing due to diversity and similarity to other eukarya

16. Alternate Form of Life Connection
Horizontal gene transfer: exchange of info between genomes
Mitochondrial ancestor of bacteria and eukarya
Chloroplasts of bacteria and green plants
Can explain inconsistency of trees
Only diagrammable as a ring