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Available at Evolution: Patterns of Similarity and Divergence Vanessa Couldridge Richard Knight.

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Presentation on theme: "Available at Evolution: Patterns of Similarity and Divergence Vanessa Couldridge Richard Knight."— Presentation transcript:

1 Available at Evolution: Patterns of Similarity and Divergence Vanessa Couldridge Richard Knight

2   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 Classification of Organisms

3   Assignment of a unique two part scientific name to each species of organism   Example: Homo sapiens   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 Binomial Nomenclature GenusSpecies

4   Corresponding structures in different species are the result of a shared common ancestor Homology

5   Anatomical features in different species resemble each other, but did not arise from a common ancestry   Example: Spider leg and mammal leg Homoplasy

6   Non-homologous features share the same function, but not necessarily the same structure   Example: Fish gills and human lungs Analogy

7   Convergent evolution   Unrelated species become similar   Parallel evolution   Related species continue to evolve similar characteristics   Divergent evolution   Related species become dissimilar Patterns of Evolution

8   Unrelated organisms evolve similar features and come to resemble one another   Example: Marsupials and placental mammals Convergent Evolution Thylacine (marsupial) Golden jackal (mammal)

9   Two or more species from a similar evolutionary history continue to evolve similar characteristics   Example: Social behaviour in bees, wasps and ants Parallel Evolution

10   Two or more species that share a common ancestor become progressively dissimilar due to differing environmental pressures   Example: Red fox and kit fox Divergent Evolution

11   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 Cladistics clubmosses spikemosses quillworths flowering plants ferns CLADOGRAM

12   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 Cladistics: Example   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 Retractable claws Involuted cheek teeth Carnassial teeth HairCATDOGLIZARDCOWSEAL   Finally, retractable claws in cats separates them from dogs

13   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

14 LUNGFISHCOWTROUT CLADISTICCLASSIFICATION   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 Systematics LUNGFISHCOWTROUT EVOLUTIONARYCLASSIFICATION

15   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 Systematic Hierarchy

16   Eight major ranks: Domain Kingdom Phylum Class Order Family Genus Species   Classification may be further divided, for example, superorder (above order) and suborder (below order) Systematic Hierarchy FRUIT FLY DomainEukaryota KingdomAnimalia PhylumArthropoda SubphylumHexapoda ClassInsecta SubclassPterygota OrderDiptera SuborderBrachycera FamilyDrosophilidae SubfamilyDrosophilinae GenusDrosophila Speciesmelanogaster


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