Week 9- Speciation
Week 9- Speciation Biology 152
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This 4 page Class Notes was uploaded by BettyAnn Mead on Sunday April 5, 2015. The Class Notes belongs to Biology 152 at University of Massachusetts taught by Peteh in Winter2015. Since its upload, it has received 52 views.
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Date Created: 04/05/15
Biology 152 04052015 Species 0 Variation in life s form not continuous Life come in discrete packages 0 These distinct entities are species 0 Objectiver real not arti cial constructs 0 Evolution must produce not only changes over time within a lineage but must also create new lineages What mechanism create and maintain new species What is a species 0 Not fully addressed until 1930 s 0 Thought of species as reproductive communities The Biological Species Concept 0 quotSpecies are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groupsquot Speciation How do species remain separate 0 What are the conditions under which a separation can evolve How do species remain separate 0 Reproductive isolating mechanisms prevent interbreeding o PrezygoticBefore Fertilization Behavioral Temporal Ecological Mechanical 0 PostzygoticAfter Fertilization Hybrid unviabilitysterility Lowered tness of hybrids What are the conditions necessary for speciation Genetic isolation 0 Gene ow restricted or blocked Evolutionary divergence 0 Genetic drift natural selection sexual selection and mutations How can the isolation step happen Allopatric A population is subdivided into two or more geographically separated parts 0 Colonization of newlyformed islands 0 Rising sea level isolates former part of mainland as an island 0 Geological change Example Mountain building river course changing 0 Formation of island habitat Example After climate change 0 Continental drift plate tectonics Sympatric A population is genetically subdivided even though it is not geographically subdivided Ecological partition 0 Chromosomal mutation polyploidy Sensory drive Sensory drive Another mechanism that can result in female predispositions to male signal characteristics Sensory Drive 0 Live in different habitats where characteristics of light are different 0 Light intensity 0 Spectral qualities Retinas of different surfperch are quotturnedquot to the characteristics of light in a particular habitat o Retinal cones can either be optimized for detecting color contrast or light intensity cones 0 Only room enough for so many comes in eyes so it s a trade off which you can do best 0 Habitat and retinal differences are correlated O 0 Species living in deep water environments have more light intensity cones Species living in shallow water environments have more color contrast cones Mate choice Male markings depend on female sensory abilities O O O Males of species that live in deep environments have marking that are best detected by brightness cones Males species that live in shallow environments have markings that are best detected by color contrast cones
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