SYSTEMATICS The reconstruction and study of evolutionary relationships

Taxonomy Two main objectives: to sort out organisms into species to classify species into higher taxonomic levels Species that appear to be closely related are grouped into the same genus. the leopard, Panthera pardus, belongs to a genus that includes the African lion (Panthera leo) and the tiger (Panthera tigris). Taxon = a named taxonomic unit at any level; (taxa = plural) ex: Mammalia is a taxon at the Class level

TAXONOMY taxonomic system developed by Linnaeus in the 18th century binomial = Genus species classification system Domain Eukarya Kingdom Animalia Phylum Chordata Class Mammalia Order Primates Family Hominidae Genus Homo species sapiens

Did King Phillip Come Over For Great Sex? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Did King Phillip Come Over For Great Sex? Domain Eukarya Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Mammalia Order Rodentia Family Sciuridae Genus Sciurus Species Sciurus carolinensis Sciurus carolinensis

Limitations of the Linnean System Many hierarchies are being re-examined based on the results of molecular analysis -Linnaean taxonomy does not take into account evolutionary relationships -The phylogenetic and systematic revolution is underway

PHYLOGENY Hypothesis of the evolutionary history of a group represented by pictures: phylogenetic trees time goes from the bottom up read from bottom up, NOT LEFT TO RIGHT branch “length” = the number of changes

Fig. 23.1 a. b. Variations of a Cladogram Gibbon Human Chimp Gorilla Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Variations of a Cladogram Gibbon Human Chimp Gorilla Orangutan Gibbon Orangutan Gorilla Human Chimp 1 1 2 2 3 Chimp 3 1 Version 1 Version 2 2 Human 3 Gorilla Orangutan Gibbon Version 3 a. b. Reproduced by kind permission of the Syndics of Cambridge University Library, Darwin’s Notebook ‘B’, ‘Tree of Life’ Sketch, p. 36 from DAR.121 D312

Phylogenies depict evolutionary relationships

Phylogenetic trees reflect the hierarchical classification of taxonomic groups nested within more inclusive groups. Fig. 25.8 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Approaches to Constructing Phylogenies Cladistics uses shared derived characteristics (synapomorphies) to classify organisms Not shared ancestral characteristics (symplesiomorphies) not overall similarity Because evolution is not steady paced, not unidirectional, may be convergent

Cladistics Examples of ancestral versus derived characters Presence of hair is a synapomorphy (shared derived feature) of mammals Presence of lungs in mammals is a symplesiomorphy (an ancestral feature); also present in amphibians and reptiles

Building Cladograms a. b. Traits: Organism Jaws Lungs Amniotic Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Traits: Organism Jaws Lungs Amniotic Membrane Hair No Tail Bipedal Lamprey Shark Salamander Lizard Tiger Gorilla Human Lamprey Shark 1 Bipedal Salamander 1 1 Tail loss Lizard 1 1 1 Hair Tiger 1 1 1 1 Amniotic membrane Lungs Gorilla 1 1 1 1 1 Jaws Human 1 1 1 1 1 1 a. b.

Can also use molecular data Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. DNA Sequence Outgroup Species B Species D Species A Species C Site 1 2 3 4 5 6 7 8 9 10 Species A G C A T A G G C G T 8:T C Species B A C A G C C G C A T 4:T G 10:T G 1:A G 8:T C 5:C A Species C G C A T A G G T G T 6:C G Homoplastic evolutionary changes 9:A G Species D A C A T C G G T G G 2:T C Homologous evolutionary changes Outgroup A T A T C C G T A T

PHYLOGENY systematists prefer monophyletic taxa a single ancestor gave rise to all species in that taxon and to no species in any other taxa

Systematics and Classification Monophyletic Group

Systematics and Classification Paraphyletic Group

Systematics and Classification Polyphyletic Group

Systematics and Classification Old plant classification system

Systematics and Classification New plant classification system

Evidence used to reconstruct phylogenies Comparative anatomy, morphology, embryology, etc. problems of homology vs homoplasy (analogy) homology = likeness due to common ancestry homoplasy or analogy = likeness due to convergent evolution

Fig. 23.9 SCIENTIFIC THINKING Question: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. SCIENTIFIC THINKING Question: How many times have saber teeth evolved in mammals? Hypothesis: Saber teeth are homologous and have only evolved once in mammals (or, conversely, saber teeth are convergent and have evolved multiple times in mammals). Phylogenic Analysis: Examine the distribution of saber teeth on a phylogeny of mammals, and use parsimony to infer the history of saber tooth evolution (note that not all branches within marsupials and placentals are shown on the phylogeny). Phylogeny of Mammals Phylogeny of Carnivores Saber-toothed marsupial weasels, canids, Bears, seals, and raccoons Saber-toothed cat Saber-toothed nimravid Saber-toothed nimravid Carnivores Mongooses Civets Hyenas Felines Marsupials Placentals Nimravids Monotremes Carnivores Result: Saber teeth have evolved at least three times in mammals: once within marsupials, once in felines, and at least once in a group of now-extinct cat-like carnivores alled nimravids. Interpretation: Note that it is possible that saber teeth evolved twice in nimravids, but another possibility that requires the same number of evolutionary changes (and thus is equally parsimonious) is that saber teeth evolved only once in the ancestor of nimravids and then were subsequently lost in one group of nimravids. (Note that for clarity, not all branches within marsupials and placentals are shown in this illustration.)

Evidence used to reconstruct phylogenies Protein comparisons DNA comparisons DNA-DNA hybridization, restriction mapping, DNA sequencing

Can Have Homoplastic Molecular Data A Cladogram: DNA

Character Mapping Once you have a phylogeny you can trace the evolution of characters or traits in that group use the rules of parsimony the simplest is the best

Parental Care Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. a: Image #5789, photo by D. Finnin/American Museum of Natural History; b: © Roger De La Harpe/Animals Animals

Parsimony and Homoplasy

Classification System

Six Supergroups Within Eukarya Eubacteria Archaea Chromalveolates Rhizaria Archaeplastida Excavata Amoebozoa Opisthokonta Excavata (organisms lacking typical mitochondria) Chromalveolata (organisms with chloroplasts obtained through secondary endosymbiosis) Archaeplastida (organisms with chloroplasts for photosynthesis) Rhizaria (organisms with slender pseudopods used for movement) Amoebozoans (organisms with blunt pseudopods used for movement) Opisthokonts (fungi, animal ancestors, and animals)

Grouping Organisms Carl Woese proposed a six-kingdom system Prokaryotes Eukaryotes

KINGDOMS Monera = Archaebacteria & Eubacteria prokaryotic Protista eukaryotic Plantae eukaryotic, multicellular, autotrophic, cell walls Fungi eukaryotic, multicellular, heterotrophic, cell walls Animalia eukaryotic, multicellular, heterotrophic, no cell walls