美国环境保护概论(三).ppt

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,*,Chapter Three:Populations,Communities,&Species Interactions,Principles of Environmental,Science-Inquiry and Applications,3rd Edition,by William and Mary Ann Cunningham,1,Chapter 3.Key Terms,McGraw-Hill Course Glossary,adaptation,Batesian,mimicry,biotic potential,carrying capacity,coevolution,commensalism,complexity,convergent evolution,divergent evolution,diversity,ecological development,ecological niche,ecotones,edge effects,environmental resistance,evolution,exponential growth,habitat,J curve,K-adapted species,keystone species,logistic growth,Mullerian mimicry,mutualism,natural selection,overshoots,pioneer species,predator,primary productivity,primary succession,r-adapted species,resource partitioning,S-curve,secondary succession,selective pressure,symbiosis,tolerance limits,2,Chapter 3-Topics,Who Lives Where,and Why?,Species Interactions,Population Dynamics,Community Properties,Communities in Transition,3,4,5,6,7,8,9,10,Part 1:Who Lives Where,and Why?,Generalists vs.Specialists,11,Tolerance Limits,Each,environmental factor,(temperature,nutrient supply,etc.)has both minimum and maximum levels beyond which a species cannot survive or is unable to reproduce.,12,Abundance and Distribution of Species,Liebig,-proposed that the single environmental factor in shortest supply relative to demand is the critical determinant in species distribution,Shelford,-added to Liebigs work by proposing that the single environmental factor closest to tolerance limits determines where a particular organism can live,13,Today we know that for many species the,interaction,of several factors,rather than a single limiting factor,determines biogeographical distribution.,Sometimes,the requirements and tolerances of species are useful indicators of specific environmental characteristics.,14,Adaptation and Natural Selection,Two types of adaptation:,Acclimation,-changes in an individual organism due to non-permanent physiological modifications,Evolution,-gradual changes in a species due to changes in genetic material and competition,Theory of evolution,-developed by Charles Darwin and,Alfred Wallace.,15,Natural selection,-genetic combinations best adapted,for present environmental conditions tend to become,abundant,Spontaneous,random,mutations,Selective pressure,-physiological stress,predation,competition,luck,16,Speciation,These 13 species of finches are descendents of a single seed-eating species.,17,The Taxonomic Naming System,18,Habitat,-the place or set of environmental conditions in,which a particular organism lives,Ecological niche,-the role played by a species in a biological community,The,Ecological Niche,19,Resource Partitioning,Over time,niches can,evolve as species develop new strategies to exploit resources.,Law of Competitive,Exclusion,:,No two species will,occupy the same niche and compete for the same resources in the same habitat for very long.,20,21,Part 2:Species Interactions,Most obvious are Predation,and,Competition,-antagonistic relationships,22,Three Types of,Symbiosis,:,Commensalism,-one member benefits,while the other is neither benefited nor harmed,Mutualism,-both members of the partnership benefit;the lichens(algae and fungi)above show mutualism,Parasitism,-a form of predation where one species benefits and the other is harmed,23,Defensive Mechanisms,24,25,Batesian Mimicry,26,Keystone species,-species that play essential community,roles(examples:mycorrhizae,giant kelp),27,Part 3:Population Dynamics,Exponential growth,-the unrestricted increase in a population(also called the,biotic potential,of a population),Carrying capacity,-the maximum number of individuals of any species that can be supported by a particular ecosystem on a sustainable basis,28,Overshoots and Diebacks,29,Population Oscillations,30,Growth to a Stable Population,31,Environmental Resistance,Environmental resistance,-factors that tend to reduce population growth rates:,Density-dependent,-linked to population size,-disease,lack of food,Density-independent,-often environmental,-droughts,floods,habitat,destruction,Intrinsic,-attributes of a species,-slow reproduction,Extrinsic,-external to a species,-predators,competitors,environmental risks,32,Part 4:Community Properties,Primary productivity,-a communitys rate of biomass production,or the conversion of solar energy into chemical energy stored in living(or once-living organisms),Net primary productivity,-primary productivity minus the energy lost in respiration,Productivity depends on light levels,temperature,moisture,and nutrient availability,.,33,Relative biomass accumulation,of major world ecosystems.,34,Abundance and Diversity,Abundance,-the number of individuals of a species in an area,Diversity,-the number of different species in an area,A useful measure of the variety of ecological niches or genetic variation in a community,Decreases as we go from the equator towards the poles,Abundance and diversity depend on total resource availability in an ecosystem.,35,Antarctic,Marine Food,Web,Complexity,-the number of species at each trophic level and the number of trophic levels in a community,36,Stability and Resilience,Stability,-a dynamic equilibrium among the physical,and,biological factors in an ecosystem or a,community,Resiliency,-the ability to recover from disturbance,Three kinds of stability or resiliency in ecosystems:,Constancy,-lack of fluctuations in composition or functions,Inertia,-resistance to perturbations,Renewal,-ability to repair damage after disturbance,37,Community structure,Distribution of members of a,population in a given space can be:,Random,-individuals live wherever resources are available,Ordered,-often the result of biological competition,Clustered,-individuals of a species cluster together for protection,mutual assistance,reproduction,or to gain access to a particular environmental resource,38,Edges and Boundaries,Ecotones,-the boundaries between adjacent habitats,Often rich in species diversity,Example:the boundary between a forest and a meadow,39,Edge effects,-the environmental and biotic conditions,at the edge of a habitat,Temperature,moisture levels,predator species,etc.,Edge effects associated with habitat fragmentation are generally detrimental to species diversity.,Core habitat,-the interior area of a habitat,Habitat not impacted by edge effects,Some species avoid edges and ecotones and prefer interior environments.,Edge vs.Core,40,Part 5:Communities in Transition,Ecological succession,-the process by which,organisms occupy a site and gradually change,environmental conditions by creating soil,shelter,shade,or increasing humidity,Primary succession,-occurs when a community begins to develop on a site previously unoccupied by living organisms,Secondary succession,-occurs when an existing community is disrupted and a new one subsequently develops at the site,41,Primary,Succession,on Land,42,Exotic Species,Sometimes communities can be completely altered by the introduction of,exotic species,.,Exotic species are often introduced by humans.,Successful exotics tend to be prolific,opportunistic species,such as goats,cats,and pigs.,Many ecologists consider exotic species invasions the most pressing hazard for biological communities in the coming century.,43,Introduced Species and Community Change,44,