美国环境保护概论（三）

1、Chapter Three: Populations, Communities, & Species InteractionsPrinciples of EnvironmentalScience - Inquiry and Applications,3rd Editionby William and Mary Ann Cunningham1Chapter 3. Key Terms McGraw-Hill Course Glossary adaptationBatesian mimicry biotic potential carrying capacity coevolution commen

2、salism complexity convergent evolution divergent evolution diversity ecological development ecological niche ecotones edge effectsenvironmental resistance evolution exponential growth habitat J curveK-adapted species keystone species logistic growth Mullerian mimicry mutualism natural selection over

3、shoots pioneer speciespredator primary productivity primary succession r-adapted species resource partitioning S-curve secondary succession selective pressure symbiosis tolerance limits2Chapter 3 - Topics Who Lives Where, and Why? Species Interactions Population Dynamics Community Properties Communi

4、ties in Transition345678910Part 1: Who Lives Where, and Why?Generalists vs. Specialists11Tolerance LimitsEach environmental factor (temperature, nutrient supply, etc.) has both minimum and maximum levels beyond which a species cannot survive or is unable to reproduce. 12Abundance and Distribution of

5、 SpeciesLiebig - proposed that the single environmental factor in shortest supply relative to demand is the critical determinant in species distributionShelford - added to Liebigs work by proposing that the single environmental factor closest to tolerance limits determines where a particular organis

6、m can live13Today 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.14Adaptation and Nat

7、ural SelectionTwo types of adaptation:Acclimation - changes in an individual organism due to non-permanent physiological modificationsEvolution - gradual changes in a species due to changes in genetic material and competitionTheory of evolution - developed by Charles Darwin andAlfred Wallace.15Natur

8、al selection - genetic combinations best adaptedfor present environmental conditions tend to becomeabundantSpontaneous, random mutationsSelective pressure - physiological stress, predation, competition, luck16SpeciationThese 13 species of finches are descendents of a single seed-eating species.17The

9、 Taxonomic Naming System18Habitat - the place or set of environmental conditions inwhich a particular organism livesEcological niche - the role played by a species in a biological communityThe Ecological Niche19Resource PartitioningOver time, niches canevolve as species develop new strategies to exp

10、loit resources.Law of CompetitiveExclusion: No two species willoccupy the same niche and compete for the same resources in the same habitat for very long.2021Part 2: Species InteractionsMost obvious are Predation and Competition - antagonistic relationships22Three Types of Symbiosis:Commensalism - o

11、ne member benefits, while the other is neither benefited nor harmedMutualism - both members of the partnership benefit; the lichens (algae and fungi) above show mutualismParasitism - a form of predation where one species benefits and the other is harmed23Defensive Mechanisms2425Batesian Mimicry26Key

12、stone species - species that play essential communityroles (examples: mycorrhizae, giant kelp)27Part 3: Population DynamicsExponential growth - the unrestricted increase in a population (also called the biotic potential of a population) Carrying capacity - the maximum number of individuals of any sp

13、ecies that can be supported by a particular ecosystem on a sustainable basis28Overshoots and Diebacks29Population Oscillations30Growth to a Stable Population31Environmental ResistanceEnvironmental resistance - factors that tend to reduce population growth rates: Density-dependent - linked to populat

14、ion 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 risks32Part 4: Community PropertiesPrimary productivity

15、 - 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 respirationProductivity depends on light levels, temperature, moisture, and nutrient

16、availability.33Relative biomass accumulationof major world ecosystems.34Abundance and DiversityAbundance - the number of individuals of a species in an areaDiversity - the number of different species in an areaA useful measure of the variety of ecological niches or genetic variation in a communityDe

17、creases as we go from the equator towards the poles Abundance and diversity depend on total resource availability in an ecosystem. 35AntarcticMarine FoodWebComplexity - the number of species at each trophic level and the number of trophic levels in a community36Stability and ResilienceStability - a

18、dynamic equilibrium among the physical and biological factors in an ecosystem or acommunityResiliency - the ability to recover from disturbanceThree kinds of stability or resiliency in ecosystems:Constancy - lack of fluctuations in composition or functionsInertia - resistance to perturbationsRenewal

19、 - ability to repair damage after disturbance37Community structureDistribution of members of a population in a given space can be:Random - individuals live wherever resources are availableOrdered - often the result of biological competitionClustered - individuals of a species cluster together for pr

20、otection, mutual assistance, reproduction, or to gain access to a particular environmental resource38Edges and BoundariesEcotones- the boundaries between adjacent habitatsOften rich in species diversityExample: the boundary between a forest and a meadow39Edge effects - the environmental and biotic c

21、onditionsat the edge of a habitatTemperature, 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 effectsSome species avoid edges and ecotones and prefer interior environments.Edge vs. Core40Part 5: Communities in TransitionEcological succession - the process by whichorganisms occupy a site and gradually changeenvironmental conditions