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Chapter 55

Biology Chapter 55.docx

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Jon Stone

1Biology Chapter 55 Biodiversity and Conservation BiologyWhat is BiodiversityPerhaps simplest way to think about biodiversity is in terms of tree of life the phylogenetic tree of all organismsWhen biodiversity increases branches and tips are added and tree of life gets fuller and bushierWhen extinctions occur tips and perhaps branches are removed the tree of life becomes thinner and sparserBiodiversity Can be Measured and Analyzed at Several LevelsoTo get a complete understanding of the diversity of life biologist recognize and analyze biodiversity on three levelsGenetic diversity is the total genetic information contained within all individuals of a species and is measured as the number and relative frequency of all alleles present in a speciesBecause no two members of the same species are genetically identical each species is the repository of an immense array of allelesSpecies diversity is based on the variety of species on EarthMeasured by quantifying the number and relative frequency of species in a particular regionAdditional aspect of species diversity called taxonomic diversity and is documented by estimating phylogeniesEcosystem diversity is the variety of biotic communities in a region along with abiotic components such as soil water and nutrientsMore difficult to define and measure than first two because ecosystems do not have sharp boundariesAttempts to measure ecosystem diversity focus on capturing array of biotic communities in a region along with variation in the physical conditions presentEx Areas around estuaries tend to have high ecosystem diversity due to combination of stream wetland intertidal neritic and upland habitats2When an estuary is dredged or filled biodiversity is affected at all three levelsoGenetic and species diversity change due to different numbers and types of individuals presentoEcosystem diversity is altered due to change in abiotic conditionsoBiodiversity is dynamicMutations that create new alleles increase genetic diversityNatural selection genetic drift and gene flow can increase or decrease overall genetic diversitySpeciation extinction increases and decreases species diversityChanges in climate or other physical conditions can result in formation of new ecosystemsHow Many Species are Living TodayoApproximately 15 M species catalogued to date represent a tiny fraction of number actually presentoGiven that only a fraction of organisms alive have been discovered to date how can biologists go about estimating the total number of species on EarthoTwo general approaches have been usedoOne is based on intensive surveys of speciesrich groups at small sitesoA second is based on attempts to identify all of the species present in a particular regionoTaxonSpecific SurveysResearchers began by estimating number of insect species that live in the canopy of a single tropical forestAfter using an insecticidal fog to knock down insects from top of a luehea seemannii tree they identified over 900 species of beetles among individuals that fellMost were new to scienceResearchers used the following logic
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