Presentation on theme: "Phylogeny and Systematics"— Presentation transcript:
1 Phylogeny and Systematics Chapter 26: (Making “Trees of Life”)
2 Macroevolutionstudies focus on change that occurs at or above the level of speciesThe origin of taxonomic groups higher than species levelHow does this occur?Evolution of new traits (novelties)mass extinctionsOpen adaptive zones (divergent evolution)
3 Currently, scientists use Morphological, biochemical, and molecular comparisons to infer evolutionary relationshipsObtained through fossil studies, DNA technology and current organisms
4 Phylogeny What is phylogeny? The evolutionary history of a group Systematics attempts to reconstruct phylogeny, by analyzing evolutionary relatedness.Use morphological and biochemical similaritiesMolecular systematics uses DNA, RNA and proteins to infer evolutionary relatedness.Different tools are used to reconstruct phylogenies called phylogentic trees.
6 SystematicsUses evidence from fossil record and existing organisms to reconstruct phylogeny (Linneaus)Binomial nomenclature Genus species keeps identity of organism universalOther taxa used to classifyDomain, Kingdom, Phylum, Class, Order, Family, Genus, species
7 Taxonomy Linnaeus ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences
11 Cladistics Cladogram is a tree with two way branch points Each branch point represents divergence from common ancestorEach branch is called a cladeCladesCan be nested within larger clades, but not all groupings or organisms qualify as clades3 types of groupingsMonophyleticPolyphyleticParaphyletic
12 Different Types of Clades Monophyletic = single ancestor gave rise to all species in the taxon; ONLY valid cladePolyphyletic = includes numerous types of organisms that lack a common ancestor; not a valid cladeParaphyletic = a grouping that consists of an ancestral species and some, but not all, of the descendants; not a valid clade
16 Making “Trees”: Morphological & molecular homologies similarities based on shared ancestriesbone structureDNA sequencesbeware of analogous structuresconvergent evolution
17 Not all Similarities Represent Common Ancestry Homologous structures indicate shared common ancestryHomologous structures are therefore evidence of divergent evolutionAnalogous structures are similar in function but not in evolutionary historyAnalogous structures are evidence of convergent evolutionIt is not always easy to sort homologous from analogous structures
18 RECALL…Convergent evolution occurs when similar environmental pressures and natural selectionProduce similar (analogous) adaptations in organisms from different evolutionary lineagesMarsupialEutherian(placental)
19 Making Evolutionary Life Trees: Illustrating Phylogeny 1. Cladistics =sorts homologous from analogous structuressorts primitive and shared derived characteristicsMakes cladograms
20 The Universal Tree of Life The tree of life is divided into three great clades called domains:Bacteria, Archaea, and EukaryaBacteriaEukaryaArchaea4 Symbiosis of chloroplast ancestor with ancestor of green plants13 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes4Billion years ago322 Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells231 Last common ancestor of all living things1Origin of life4Figure 25.18
21 A shared primitive character a homologous structure that is shared by all groups we are trying to defineA shared derived characterA new evolutionary trait unique to a particular clade(s)Making Cladograms Activity Time
25 Phylograms In a phylogram DrosophilaLanceletAmphibianFishBirdHumanRatMouseCenozoicMesozoicPaleozoicProterozoic54225165.5Millions ofyears agoIn a phylogramThe length of a branch in a cladogram reflects the number of genetic changes that have taken place in a particular DNA or RNA sequence in that lineageInvolves timing cladograms do NOT!