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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