I Species and Speciation A Speciation is the process that produces new species B Gene flow can lead to speciation II Species A Species is a group of organisms that can evolve or change B A fundamental biological unit C Defined by the ability or inability of two individuals to exchange genetic material by producing fertile offspring D Become extinct E Give rise to new species 1 Living on Earth today are only about 1 2 of the species that exist in the world scientists predict III Species Plot A IV Biological Species Concept BSC A Alfred Russel Wallace 1865 1 First proposed it B Ernst Mayr 1 Refined it V Morphospecies Concept C Is there enough genetic similarities in those species to produce successful offspring 1 To test this scientists must actually mate species D Groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups A Stated simply the morphospecies concept holds that members of the same species usually look alike which is why natural history guidebooks are useful B States that members of the same species usually look alike C More practical D Not perfect E Not always real accurate F Limitations in appearance G Good start but then BSC is needed H VI Ring Species A An unusual but interesting geographic pattern shown by ring species highlights another shortcoming of the BSC B Limitation in BSC C May not be part of the same species but can be genetically similar gene flow D Hybridization or interbreeding VII Limitations of the BSC A Difficult to apply in real world 1 Have mating event and watch and see what happens to offspring B Cannot be applied to asexual or extinct organisms 1 Cando mating event between fossils C Does not account for genetic exchange in ring species D Does not account for hybridization successful reproduction between two different species in plants 1 Interbreeding between different species seen often in plants 2 The species maintain distinct appearances indicating that natural selection works against the hybrid offspring VIII Improving the BSC A Ecological species concept ESC 1 A species can sometimes be characterized by its ecological niche a Ecological Niche a complete description of the role the species plays in its environment its habitat requirements its nutritional and water needs and the like i Impossible for two species to coexist in the same location if their niches are too similar ii Can be separated this way by where they live what they eat B Evolutionary species concept EvSC 1 Members of a species all share a common ancestry and a common fate with eachother a Evolutionary history more information C These two concepts broaden and generalize the BSC IX Reproductive Isolation A Pre zygotic isolating factors act before the fertilization of an egg 1 Behavioral dance 2 Physical 3 Time temporal 4 Space ecological 5 Among animals species are often behaviorally isolated meaning that individuals only mate with other individuals based on specific courtship rituals songs and other kinds of behaviors B Post zygotic factors come into play after fertilization 1 Genetic incompatibility a Different numbers of chromosomes zygote does not develop offspring are sterile X Speciation the evolutionary process of genetic divergence A Speciation occurs when two populations that are genetically diverging become reproductively isolated from each other B XI Allopatric Speciation A The process usually begins with the creation of allopatric literally different place populations populations that are geographically separated from each other B Geographic model of speciation C Physical separation between two populations D Subspecies may form 1 Exposed to different environments mutations 2 Adding a further designation after its species name E Two basic mechanisms 1 Dispersal 2 Vicariance a Some individuals colonize a distant place such as an island far from the main source population b Organisms move XII a A geographic barrier arises within a single population separating it into two or more isolated populations b Formation of a physical variant Dispersal Derived Speciation Peripatric Speciation A Dispersal is important in a specific kind of allopatric speciation B Members of the parent species mainland population become separated by physical barriers 1 Living on different parts of a land mass 2 Migrating to an island and forming a new population there a Island populations evolve faster than those located on the mainland C Adaptive Radiation 1 Rapid peripatric speciation due to many new habitats opening up Darwin s finches XIII Dispersal Derived Speciation Adaptive Radiation A A bout of unusually rapid evolutionary diversification in which natural selection accelerates the rates of both speciation and adaptation B Adaptive radiation occurs when there are many ecological opportunities available for exploitation C Rapid evolution in which natural selection accelerates the rate of speciation and adaptation D Occurs when there are many new ecological niches available XIV Vicariance Derived Speciation A Physical barrier forms in that speciation B XV Co Speciation A A process in which two groups of organisms speciate in response to each other and at the same time B Two groups of organisms speciate in response to each other and at the same time C 1 Each species of pocket gophers have their own species of chewing lice D How did malaria come to infect humans in class discussion XVI Sympatric Speciation A The term we use to describe populations that are in the same geographic location is sympatric literally same place B Doesn t require separation by a physical barrier 1 But it changes ecologically C Describes populations that are in the same geographical location same place D Is this possible some scientists have doubts 1 Gene flow can negate the genetic divergence a Natural selection has to act strongly to counteract gene flow E Examples 1 The birds specialized for eating different size seeds shown yesterday 2 Fish isolated lakes in the mountains of Cameroon a Lakes have a variety of species b All species in a single lake are each other s closest relatives c The species live in the same geographical area F XVII Instantaneous Speciation A Typically cases of such instantaneous speciation are caused by hybridization between two species in which the offspring are reproductively isolated from both parents 1 Very rare and usually seen in plant world 2 Example of hybridization 3 Usually caused by a hybridization between two species 4
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