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Lecture 19

Lecture 19 - Reconstructing Evolution

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Esteban Parra

ANT203Y5 – BiologicalAnthropology Lecture 19 – January 9, 2014 Reconstructing Evolution Some Important Terms - Systematics o The scientific classification of the diversity of organisms o Uses classification systems to help understand how organisms evolved - Within Systematics o Taxonomy deals with the theory and practice of classifying organisms o Phylogenetics deals with the identification and understanding of species relationships. Linnaean System of Taxonomy - Developed by Carolus Linnaeus (1707-1778) o Groups organisms into taxonomic categories - Uses Binomial Nomenclature in which an organism is assigned o Two names, a generic name (Genus) and a specific name (Species) o Both are italicized and only the genus is capitalized  For example Pan troglodytes (Chimpanzee) Goals of Classification - One of the main goals of systematics is to elucidate the ancestral relationships of organisms, and also to understand their evolutionary history. - I recommend that you visit the TREE OF LIFE web project, available at: o - However, this is not an easy task, as we will review below. Homology and Homoplasy - Homology: Presence of traits or features that are a result of common ancestry o For example the tetrapod limb - Homoplasy: Presence of similar traits or features that are not a result of common ancestry o This may cause you to just build trees that do not correspond to natural categories (a major problem in classifications) o For example the wings of bats, insects and birds o The evolution of superficially similar features in lineages that are very dissimilar or unrelated, such as the above example, is called Convergent evolution or Convergence - Two additional terms related to this are…. Homologous vs.Analogous Traits - Homologous traits: Traits found in different species that have a common origin (although they may have a different function). - Analogous traits: Traits found in different species that have the same or similar function, but have different evolutionary origins. o These are the one that create problems ANT203Y5 – BiologicalAnthropology Lecture 19 – January 9, 2014 Convergent Evolution - Wings of insects, birds and bats (analogous traits Convergence inAquatic Lifestyle - Because of adaptive radiation, mammals have been colonized differently - Birds themselves descends from dinosaurs, and then evolved and colonized into the seas Convergence in flight - From reptile, there were evolved independently, or from the dinosaurs - Some mammals went in the same paths, such as the bats Example: of Convergent Evolution: Placental Mammals and Marsupials - Some of them are remarkably similar! o I.e. the mole and the marsupial mole - They had to tackle similar evolutionary problems and therefore evolved in similar ways - Different organisms have to adapt, and tackle the same problems and there is a convergent evolution  create a huge problem ANT203Y5 – BiologicalAnthropology Lecture 19 – January 9, 2014 Problems withAnalogous Traits - Using analogous traits can result in wrong classifications, which don’t represent accurately the evolutionary relationships of organisms. Example of Homologous Traits ANT203Y5 – BiologicalAnthropology Lecture 19 – January 9, 2014 - Tetrapod limb; all of them show common ancestry but in fact have evolved in many different ways - Important Issues to Consider When Classifying Organisms - To which extent can the organisms included in a group be considered as a “natural group” (e.g. groups that include the ancestral and all the descendant taxa)? - What type of traits are used for classification? o Primitive (traits that are similar to the ancestral condition) or derived (different from the ancestral condition). o Are the traits shared between different members of the group, or are unique to only one taxon? Main Terms to Describe Grouping o
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