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section 52.2.doc

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Richard Brown

52.3 • biome: terrestrial environment defined by grown forms of plants (forests, tundra) o plant distribution influenced by temp and rainfall o one set of graphs plots seasonal patterns of temp and precipitation at a site in a biome o some graphs show activity patterns of different kinds of organisms / year; levels of biological activity shown by width of horizontal bars o species richness: number of species present in communities • boundary btwn biomes is arbitrary; gradually merge into another • tundra biome: arctic and high elevations in mountains everywhere o in Arctic t, vegetation is underlain by permafrost—soil who water is permanently frozen; soil may thaw in short summer  little precipitation but very wet b/c water can NOT drain through permafrost  plant grow for few months/year  animals migrate into area for summer or are dormant for most of year o tropical alpine t: photosynthesis and most bio activities continue (slowly)  more plant forms present • boreal forest: toward equator from Arctic t, lower elevations on mountains o winders long and cold, summers short, warm o evergreen tress b/c ready to photosynthesize as soon as it gets warm o NH: has evergreen coniferous gymnosperms; SH: southern beeches o Temperate evergreen forests: grow along western coasts of continents at middle to high latitudes; winters mind and wet, summers cool and dry; earth’s tallest trees o few tree species; moose, hares; seeds of conifersrodents, birds, insects • temperate deciduous forest: eastern NA, eastern Asia, Europe o temps fluctuate btwn winter and summer, precipitation evenly distributed o deciduous trees dominate; more tree species than boreal o many genera or plants+animals shared in those 3 separate regions • temperate grassland: areas dry for much of year o hot summers, cold winters; converted to agriculture o in some, most precipitation falls in water, others in summer o vegetation = simple – perennial grasses, sedges, forbs (colourful) o plants adapted to grazing and fire; store energy underground and resprout • cold desert: dry regions at middle to high latitudes; esp in continents in rain shadows of mountain ranges o seasonal temp changes great; dominated by few species of low-growing shrubs; annual productivity is low b/c soils dry rapidly in spring o surface of soil recharged w/ moisture in winter, plant growth concentrated in spring o poor in species of most taxonomic groups, but lots of seeded plantssupports seed- eating animals • hot desert: two belts – 30 N and S – where air descends, warms, picks up moisture o scarce rainfall in summer, winter rains from ocean storms o richer, structurally more diverse vegetation (cacti) o annual plants germinate+ abundantly grow; pollination+dispersal of fruits o rodents, termites, ants, lizards, snakes • 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 52.4 • 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, mounta
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