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Biomes and Biogeographic Regions

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Q Chen

on 10 December 2012

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Transcript of Biomes and Biogeographic Regions

Alfred Russel Wallace Biogeography biogeographic regions scientific study of the patterns of distribution of populations, species, and ecological communities across Earth several distinct continental-scale regions of Earth, each with their own characteristic biota biotic interchange vicariant events human influence continental drift phylogenetic taxonomy division of a population due to the appearance of a physical barrier, and not due to migration or dispersal Cook Strait Bali Lombok Biomes an environment that is defined by its climatic and geographic attributes and characterized by ecologically similar organisms, particularly its dominant plants developed and divided the populations of the flightless weevil and 60 other animal species that normally cannot cross the strait boundaries are drawn where distribution of species change drastically over short distances Malay Archipelago
Bali and Lombok have similar climates and geographical attributes
but the flora and fauna are very different across the strait From this, Wallace established the foundations of biogeography. dispersion of species into a region where they had not previously inhabited when landmasses combine or fuse Central American Landbridge humans moving species across distances that they cannot cross naturally "biodiversity hotspots"
have a lot of endemic species Most species are confined to one biogeographic region due to barriers (region borders). endemic species species only found within a certain region Madagascar 3 Main Influences on Biogeographic Patterns biotic interchange
vicariant events
human influence 2 Scientific Advances Changed Biogeography acceptance of the theory of continental drift
development of phylogenetic taxonomy theory that over billions of years, Earth's continents have made gradual movements explains the patterns of discontinuous distribution of species through history evolutionary relationships between organisms are organized into phylogenetic trees area phylogenies show the dispersal and distribution of organisms, and identify geographical origins tropical evergreen forest species' identities across a geographically distributed biome may differ, but they share similar adaptations due to the biome biome boundaries are arbitrary, and definitions are general (variations can be found within biomes) the same biome may be found in widely separated parts of the world, depending on distribution of climatic conditions covers less than 2% of Earth’s surface, but contains over half of all known biota species highest overall productivity of ecological communities; however, most mineral nutrients are in the vegetation, rather than in the soil rainforests are currently being deforested or converted to agricultural land at a rate of ~20 million hectares per year tundra temperate grasslands boreal & temperate evergreen forest arctic tundra is covered with permafrost
(soil permeated with permanently frozen water) alpine tundra does not have permafrost; most biological activities continue throughout the year temperate deciduous plants have hairy leaves to trap heat
flowers follow sun’s movement
some animals are summer migrants or dormant for most of the year
thick fur/feathers on mammals and birds, may change colour in order to camouflage hot desert cold desert chaparral thorn forest & tropical savanna in the boreal forest: winters are long and cold, summers short and relatively warm
favours evergreen trees; ready to photosynthesize as soon as temperatures warm in the temperate evergreen: winters are mild but wet, while summers are cool and dry tropical deciduous southern Appalachian mountains of USA, eastern China and Japan (not covered by glaciers during Pleistocene) are the areas richest in species some animals (including many birds) migrate
others fatten up during autumn and hibernate
many resident insect species pass winter in a state of diapause relatively dry throughout much of the year structurally simple, but contains many perennial grasses and other herbaceous plants (forbs) topsoil usually rich and deep; most of the world’s temperate grasslands are now used for agriculture Adaptations to hot and dry climate: flora:
taproots and shallow, extensive roots
small wax-covered leaves; CAM photosynthesis
most perennials go dormant during dry season
seeds tend to be heat- and drought-resistant fauna:
small animals are inactive during the day
estivation (metabolic dormancy) in small invertebrates
desert mammals have fewer sweat glands, produce highly concentrated urine, many require no water beyond that from food “high and dry”; dry regions at high elevations usually in the rain shadows of mountains burrowing behaviour is common in animals to escape cold temperatures (contrast hot desert fauna, which burrow to escape extreme heat) found on the western sides of continents (usually windward of mountains) and shore areas with nearby cold ocean currents vegetation is adapted to periodic fires; some species of seeds do not germinate until after a fire shrubs carry out growth/photosynthesis in early spring, when insects are active and birds breed thorn forests contain many plants similar to hot deserts (spiny shrubs, small trees which drop their leaves during the dry winters) savanna has expanses of grasses/grasslike plants, with scattered individual trees
supports herds of grazers/browsers and carnivores
if not grazed, browsed, or burned, tropical savannas typically revert back to thorn forests Organisms adapt to cold temperatures: taller trees support much more flora and fauna soils here are among the best in the tropics for agriculture, as it contains more nutrients than wetter soil
most tropical deciduous forests worldwide have been cleared for agriculture/grazing supports herds of large grazing animals, as the vegetation is adapted to being grazed and burned Dealing with the winter cold: rainy seasons are longer than thorn forests most species-rich of all biomes, as all seasons are suitable for growth BIOMES fossil evidence, geologic age, and plate tectonics support this theory Alfred Wegener, 1915 tundra
boreal and temperate evergreen
temperate deciduous
temperate grasslands
hot desert
cold desert
thorn forest and tropical savanna
tropical deciduous
tropical evergreen
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