BIOB50 Chapter 3 Review

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Biological Sciences
Marc Cadotte

Chapter 3 The BiosphereThe American SerengetiTwelve Centuries of Change in the Great Plains A Case StudyGreat Plains located in central North America is different from Serengeti Plain of Africalow biological diversity in Great Plainsgenetically identical crop plantsfew species of domesticated herbivoresdiverse wild animals in Serengetilatitudinal elevational shifts in biological communitiesspecies compositionvegetation followed retreating ice northwardcolonized newly exposed areamegafauna are animals larger than 45 kgthese large mammals went extinct in Great Plains about 1000013000 years agochanges in climate in extinction period were rapidled to changes in habitat food supply that negatively affected animalsarrival of humans increases the death rate of animals still controversialIntroductionbiosphere is zone of life on Earth located between lithospheretropospherelithosphere Earths surface crustupper mantletroposphere lowest layer of atmosphereTerrestrial BiomesBiomeslargescale biological communities shaped by physical environmentreflect climatic variationcategorized by most common forms of plants distributed across large geographic areascategorization does not take taxonomic relationship among organisms into accountrelies on similarities in morphological responses of organisms to physical environmentbiomes in different continents show similar responses to climatic forcesTropical forestshave multiple verdant layershigh growth rateshigh species diversityvegetation reaches higher heightgreater aboveground biomassPolar desertsharsh climate of high windslow temperaturesdry soiltiny plants cling to groundlow surface biomassterrestrial biomes are classified by1 Growth form of dominant plantssizemorphology2 Characteristic of leavesi Deciduousnessseasonal shedding of leavesii Thicknessiii Succulencedevelopment of fleshly water storage tissuesplants instead of animals are used to categorize terrestrial biomesplants are immobilecope with environmental extremesbiological pressures competition for water nutrientlight in order to occupy a site for a long timeplant growth forms are good indicators of physical environmentreflect climatic zonesrates of disturbance fire frequencymobility of animal allows them to avoid exposure to adverse environmental conditionscomposition of microbial communities reflects physical conditionbut tiny size of microorganisms along with rapid temporalspatial changes in their composition makes them impractical for classifying biomesplants develop different forms in response to selection pressures of terrestrial environmentselection pressures include aridity highsubfreezing temperatures intense solar radiation nutrientpoor soil grazing by animals crowding by neighbourdeciduous leaves help plants to face seasonal exposure ranging from subfreezing temperatures to dry periodswoody tissues increase heightability to capture sunlightprotect tissues from damage by wind or large amounts of snowPerennial grassesgrow from bases of leaveskeep vegetativereproductive buds below soil surfacefacilitate tolerance of grazing fire subfreezing temperaturedry soilssimilar plant growth forms appear in similar climatic zones on different continents for plants that are not genetically relatedthis type of evolution is convergence when there are similar growth forms among distantly related species in response to similar selection pressuresTerrestrial biomes reflect global patternsclimatic zones determine distribution of terrestrial biomesTropicshigh rainfallwarm invariant temperatureSubtropical region
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