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L5 ch 25 - Lecture 5 Ch-25 Origin of Species Overview Known...

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Lecture 5: Ch-25 Origin of Species Overview: Known number of species: about 1.4 million Estimates of unidentified species range from: 2 to 100 million Difficulty in identifying a “species” A single species may exist in 2 distinct populations that are in the slow process of evolving into 2 or more different species Speciation Appearance of new species Source of biodiversity When two populations are separated for long enough, they will likely accumulate significant changes that will allow them to become separate species. Species concepts: There are different ways of distinguishing species based on various concepts. Phylogenetic: Species are identified by having a unique combination of traits Historically used physical traits Now can use DNA sequences Advantage Can be applied to all organisms Disadvantages: Difficult to decide how many traits you want to focus on. Difficult to analyze traits that vary in a continuous way Degree of dissimilarity between species may be difficult to determine Sometimes members of the same species can look very different AND members of different species can look very similar Example: Dendrobates tictorius has different-colored morphs with different appearances but are the same species; Rana pipiens (North leopard frog on the right of figure) and R. utricularia (South leopard frog on the left) look the same but are different species.
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