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Vanessa Couldridge Richard Knight Available at http://planet.uwc.ac.za/nisl/Eco_people/Presentations/ http://en.wikipedia.org/wiki/Image:Darwins_first_tree.jpg Evolution: Patterns of Similarity and Divergence Species are grouped according to their similarity or evolutionary history First performed by Linnaeus on the basis of physical characteristics Molecular techniques more widely used today http://en.wikipedia.org/wiki/Image:Carolus_Linnaeus_%28cleaned_up_version%29.jpg Classification of Organisms Assignment of a unique two part scientific name to each species of organism Example: Homo sapiens Genus Species Scientific name is written in italics and the genus name begins with a Capital Letter Can be abbreviated, e.g. H. sapiens and H. habilis Homo sp. means a single species in the genus Homo Homo spp. means more than one species in the genus Homo http://www.msu.edu/~heslipst/contents/ANP440/images/Skhul_5.jpg Binomial Nomenclature Homology Corresponding structures in different species are the result of a shared common ancestor http://en.wikipedia.org/wiki/Image:Evolution_pl.png Anatomical features in different species resemble each other, but did not arise from a common ancestry Example: Spider leg and mammal leg http://en.wikipedia.org/wiki/Image:Legs.jpg http://en.wikipedia.org/wiki/Image:Brachypelma_Smithii.jpg Homoplasy http://interactive.usask.ca/Ski/media/stills/fisheries/t_fish_gills01.jpg Non-homologous features share the same function, but not necessarily the same structure Example: Fish gills and human lungs http://www.wpclipart.com/medical/anatomy/lungs_diagram.png Analogy Patterns of Evolution Convergent evolution Parallel evolution Unrelated species become similar Related species continue to evolve similar characteristics Divergent evolution Related species become dissimilar Unrelated organisms evolve similar features and come to resemble one another Example: Marsupials and placental mammals Thylacine (marsupial) Golden jackal (mammal) http://en.wikipedia.org/wiki/Image:Golden_Jackal_sa02.jpg http://en.wikipedia.org/wiki/Image:Thylacine.jpg Convergent Evolution Two or more species from a similar evolutionary history continue to evolve similar characteristics Example: Social behaviour in bees, wasps and ants http://en.wikipedia.org/wiki/Image:Bee_swarm_on_fallen_tree03.jpg http://en.wikipedia.org/wiki/Image:Oecophylla.jpg Parallel Evolution Two or more species that share a common ancestor become progressively dissimilar due to differing environmental pressures Example: Red fox and kit fox http://en.wikipedia.org/wiki/Image:Vulpes_macrotis_standing.jpg http://en.wikipedia.org/wiki/Image:Vulpes_vulpes_sitting.jpg Divergent Evolution Cladistics Method of classifying organisms according to common ancestry, based on their dichotomous branching in an evolutionary tree Uses shared derived characteristics Tree of relationships is called a cladogram Subset of related organisms is called a clade CLADOGRAM Cladistics: Example Cladogram of five vertebrates: lizard, cow, seal, dog, cat The presence of hair can be used as the first branching point to separate the lizard from the others The presence of involuted cheek teeth in the cat, dog and seal, but not the cow, determines the next branching point The cat and dog can be separated from the seal based on the presence of carnassial teeth Finally, retractable claws in cats separates them from dogs CAT DOG SEAL COW LIZARD Systematics Method of classification that takes into account: Splitting of branches in the phylogenetic tree Major evolutionary changes Systematics differs to cladistics in that it weighs derived characters according to their degree of evolutionary significance, whereas cladistics treats all derived characters equally Systematics Consider the relationship between the cow, lungfish and trout as an example In the cladistic approach, cows and lungfish are more closely related to each other than either is to the trout, because they share a novel feature (internal nares) In the systematic approach, the lungfish and the trout are more closely related to each other than either is to the cow, because the cow is a mammal and the other two are both fishes COW LUNGFISH TROUT CLADISTIC CLASSIFICATION COW LUNGFISH EVOLUTIONARY CLASSIFICATION TROUT Organisms classified according to a series of ranks that become progressively less inclusive Originally proposed by Linnaeus, who identified Three kingdoms: Animal, vegetable, mineral Five ranks: Class, order, genus, species, variety http://en.wikipedia.org/wiki/Image:Systema_Naturae_cover.jpg Systematic Hierarchy Eight major ranks: Domain FRUIT FLY Kingdom Phylum Class Order Family Genus Species Domain Kingdom Phylum Subphylum Class Subclass Order Suborder Family Subfamily Genus Species Eukaryota Animalia Arthropoda Hexapoda Insecta Pterygota Diptera Brachycera Drosophilidae Drosophilinae Drosophila melanogaster Classification may be further divided, for example, superorder (above order) and suborder (below order) http://en.wikipedia.org/wiki/Image:55542main_maflies_med.jpg Systematic Hierarchy