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BIOL 240 (20)
Lecture 18

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Department
Biology (Sci)
Course
BIOL 240
Professor
Christa Scholtz
Semester
Fall

Description
 chaparral: western sides of continents, mid-latitude, cool ocean currents flow off-shore o cool, wet winters; warm, dry summers o dominant plants: low growing shrubs and trees with tough evergreen leaves o annual plants abundant, produce seeds that fall into soil small rodents o vegetation is naturally adapted to survive periodic fires  thorn forest: equatorial sides of hot deserts o climate: semiarid – little rain in winter, heavy rain in summer o plants similar to those in hot deserts; spiny shrubs+small trees=dominant (deciduous) o tropical savanna: expanses of grasses/grass-like plants with scattered trees  supports grazing and browsing mammals, large carnivores  if vegetation is not grazed, it reverts to dense thorn forest  tropical deciduous forest: closer to equator where length of rainy season increases o taller trees, fewer succulent plants than TF; richer in plant+animal species o most trees lose leaves during long, hot dry season, flower while leafless, pollinated by animals; during hot dry season, biological activity is intense o best soils for agriculture b/c contains more nutrients than wetter areas  most cleared for agriculture and cattle grazing  tropical evergreen forest: equatorial regions; total rainfalls >250cm/year; dry season <3mths o richest in # of species of animals+plants; highest overall productivity of all o most mineral nutrients are tied up in vegetation; soil needs fertilizers for agriculture o on mountain slopes, trees shorter than lowland tropical trees; leaves are smaller; more epiphytes: plants that grow on other plants, getting nutrients+moisture from air)  climate important, but other factors (soil fertility, fire) influence structure+vegetation of area  Wallace: correctly deduced that dramatic differences in flora+fauna were related to depth of channel separating two areas channel so deep it remained barrier to movement o established foundations of biogeography: scientific study of patterns of distribution of populations, species, ecological communities on earth and geological history of area influences kinds of organisms found there o Wallace’s Line: line he drew through Malay Archipelago  flora, fauna, and microorganisms (the biota) of world allow us to divide earth into biogeographic regions: based on taxonomic composition of organisms living in them o boundaries are set where species change dramatically over short distances o biotas differ b/c barriers (oceans, mountains) restrict dispersal of animals btwn o interchanges not been frequent/massive enough to eliminate striking differences that have resulted from speciation+extinction within each region: most species confined  a species found only within certain regions is endemic to region (ex vascular plants of Madagascar b/c of water barriers)  biotas of major biogeographic regions are very different from eachother  3 scientific advancements changed biogeography o acceptance of continental drift theory  Linnaeus believed all organisms created in one place (Paradise) from which they dispersed, and organisms distributed b/c of massive dispersal  Wegner: continental draft; continents changed position over time  280,000,000 yrs ago, continents united to form single land mass (Pangaea), then began to separate, and species evolved o development of phylogenetic taxonomy  biogeographers transform phylogenetic trees into area phylogenies by replacing names of taxa on a tree with names of places where those taxa live(d) o development of island biogeography theory to explain why ocean islands have fewer species that mainland area of same size  2 processes: immigration of new species, extinction of species already present  species pool: list of species on mainland that might possibly colonize  first colonists = new species; as # of species on island increases, they will be members of species already present; rate of arrival of new species decreases until reaches 0
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