PHYOGENY & THE Tree of life Represent traits that are either derived or lost due to evolution

definitions evolutionary history of a species or group of species discipline focused on classifying organisms & determining their evolutionary relationships Phylogeny Systematic s

Taxonomy how organisms are classified and named each step called a taxon (plural: taxa)

BINOMIAL NOMENCLATURE Man’s Genus species: Homo sapiens used to avoid ambiguity the Latin scientific name for each individual species is the Genus species portion of taxonomy

3 DOMAINS DOMAIN ARCHAEA –Prokaryotes –many live in Earth’s extreme environments –as molecularly close to eukaryotes as Domain Bacteria –includes multiple kingdoms

(notice position of domain Archaea)

Domain Archaea methanogenthermophile

Domain Bacteria Prokaryotic very diverse group use every major mode of nutrition & metabolism beneficial: photoautotrophs, alcoholic fermentation, Vit K production pathologic: strep throat, flesh-eating disease, ulcers, Rheumatic fever

Domain Bacteria Gram Positive Bacteria Streptococcus (cocci) Gram Negative Bacteria Legionella pneumophilia (rods)

Domain Bacteria Spirochetes (spirillia)

Domain Eukarya Eukaryotic cells –more complex, become specialized –able to form multicellular organisms –greatest diversity

Domain Eukarya PlantsFungi

Domain Eukarya AnimalProtozoa

Domain Eukarya Algae CellsAlgal “bloom”

Linnean Classification

PHYLOGENETIC TREES show the evolutionary history of a group of organisms represented by a branching diagram each branch point represents the divergence of 2 evolutionary lineages from a common ancestor Representation to show that speciation has occurred

Phylogenetic Trees Branch Point relatedness of any two groups is shown by how recently two groups has a common ancestor

What you can learnWhat you cannot learn patterns of descent common ancestors does not show phenotypic similarity cannot tell ages of species based on where branches are in the “tree” sister taxa did not evolve from each other; they have a common ancestor (that could be extinct) Phylogenetic Trees

Uses of Phylogenetic Tree 1.If “close” relatives found they could be source of beneficial alleles that could be transferred to hardier taxa via genetic engineering 2. Using DNA samples are now able to differentiate legal species from illegal species of whale, tuna

Phylogenies are inferred from morphological & molecular data Homology: similarity in characteristics resulting from a shared ancestry

Homologous Chromosomes in same species When chromosomes duplicate in S Phase of Cell Cycle see genes in same loci of each sister chromatid

Homologous Chromosomes across Species with Common Ancestor Genes or certain DNA sequences also homologous if they descended from sequences carried by a common ancestor

Organisms that share very similar morphologies or DNA sequences are likely to be more closely related than organisms with vastly different structures There are examples of organisms that look very different but have very similar DNA sequences because species underwent adaptive radiation.

Homology vs. Analogy Analogy is similarity due to convergent evolution: occurs when similar environmental pressures & natural selection produce similar (analogous) adaptations even though organisms have different ancestors.

The more complex the structure found in 2 species the more likely it is that they have a shared ancestor

Molecular Evidence of Evolutionary Relationships DNA sequence similarities have been documented among prokaryotes & eukaryotes: (comparative genomics) High degree of sequence similarity noted in some eukaryotic nuclear genes to Archaea & mitochondrial genes are similar to Bacteria

Using DNA to map an organism’s evolutionary history The more recently 2 species have branched from a common ancestor, the more similar their DNA sequences should be The longer ago 2 species have been on separate evolutionary paths, the more their DNA should have diverged

Review: Phylogeny can be inferred from –the fossil record, –morphological homologies –molecular homologies

Phylogenetic Trees vs. Cladograms A phylogenetic tree represents the evolutionary relationships among a set of organisms or groups of organisms, called taxa. The tips of the tree represent groups of descendent taxa (often species) and the nodes on the tree represent the common ancestors of those descendants. Two descendents that split from the same node are called sister groups. Evolutionary trees depict clades – a group of organisms that includes an ancestor and all descendants of that ancestor; Shared ancestral characters group organisms – You can think of a clade as a branch on the tree of life.

character that originated in an ancestor of the taxon an evolutionary novelty unique to a clade. Shared Ancestral Character Shared Derived Character

Shared Ancestral Character Shared Derived Character

How to Build a Cladogram onu/cladograms/Open-This-File.swf onu/cladograms/Open-This-File.swf

How to Construct a Phylogenetic Tree

Making a Phylogenetic Tree SHOULD BE POSSIBLE TO DETERMINE THE CLADE ANY SHARED DERIVED CHARACTER 1 ST APPEARED Construct a CHARACTER TABLE: –1 axis has list of organisms, 1 has characters

CHARACTER TABLE FROGIGUANADUCK-BILLED PLATYPUS KANGAROOBEAVER AMNION HAIR, MAMMARY GLANDS GESTATION LONG GESTATION

Important step in cladistics is the comparison of the –Ingroup: the taxa whose phylogeny is being investigated –Outgroup: the taxon that diverged before the lineage leading to the members of the ingroup –Use to identify the derived characters that define the branch points in the phylogeny of the ingroup

PHYLOGENETIC TREES WHEN CONSTRUCTING A PHYLOGENETIC TREE, SCIENTISTS USE PARSIMONY, LOOKING FOR THE SIMPLEST EXPLANATION FOR OBSERVED PHENOMENA

SYSTEMATISTS USE MANY KINDS OF EVIDENCE, BUT EVEN THE BEST TREE REPRESENTS ONLY THE MOST LIKELY HYPOTHESIS

Shared characters are used to construct phylogenetic trees The phylogenetic tree of reptiles shows that crocodiians are the closest living relatives of birds