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1、国外动物学38 Still waters run deep.流静水深流静水深,人静心深人静心深 Where there is life,there is hope。有生命必有希望。有生命必有希望EcologylEcology investigates the interactions among organisms and between organisms and their environment.Hierarchy of EcologylOrganism level studies focus on individuals.lPhysiological or behavioral eco
2、logylPopulation level studies examine groups of conspecific organisms living in a particular area.Hierarchy of EcologylCommunity level studies investigate interactions between the populations of various species in an area.lSpecies diversity-#of different specieslInteractions predation,parasitism,com
3、petition,symbiotic associations.lEcosystem level studies examine how a community interacts with the physical environment.Environment and NichelAn animals environment includes all of the conditions that affects survival and reproduction.lAbiotic factors(nonliving)soil,air,water,sunlight,temperature,p
4、H etc.lBiotic factors(living)food items,predators,parasites,competitors,mates,hosts etc.Environment and NichelEnvironmental factors that are directly utilized by an animal are resources.lSpace(nonexpendable)lFood(expendable)Environment and NichelAn animals habitat is the space where it lives.lSize i
5、s variablelRotten log is a habitat for carpenter ants.lForest&adjacent meadow is a habitat for deer.Environment and NichelThe habitat must meet the requirements for life.lTemp,salinity,pH etc.lThe unique multidimensional relationship of a species with its environment is its niche.Environment and Nic
6、helGeneralists can withstand a variety of environmental conditions.lSpecialists can only tolerate a narrow range.Environment and NichelThe fundamental niche describes the total potential role that an organism could fill under ideal circumstances.lThe realized niche describes the actual role an organ
7、ism fills.lSubset of the fundamental niche.lAffected by competitionPopulation EcologylPopulation ecology is the study of populations in relation to environment,including environmental influences on population density and distribution,age structure,and variations in population size.PopulationslA popu
8、lation is a reproductively interactive group of animals of a single species.lA few individuals may migrate between populations.lAdds gene flowlPrevents speciation.lNumerous small populations may be connected in this way.lMetapopulationLife TableslA life table is an age-specific summary of the surviv
9、al pattern of a population.lLife tables usually follow the fate of a cohort a group of individuals of the same age from birth until all have died.Survivorship CurveslA survivorship curve is a graphic way of representing the data in a life table.lThe survivorship curve for Beldings ground squirrels s
10、hows that the death rate is relatively constant.Survivorship CurveslSurvivorship curves can be classified into three general typeslType I high survival early in life indicates parental care of fewer offspring.lType II constant death rate over life spanlType III drops sharply at start indicating high
11、 death rate for young;lots of young,no care.Age StructurelPopulations that contain multiple cohorts exhibit age structure.lMore individuals in the younger cohorts indicates a growing population.Life History DiversitylSpecies that exhibit semelparity,or“big-bang”reproduction reproduce a single time a
12、nd die.lSalmonlAgavelFavored in unpredictable climates.Life History DiversitylSpecies that exhibit iteroparity,or repeated reproduction,produce offspring repeatedly over time.lLizards often start reproducing during their second year and will produce eggs every year of their lives.lFavored in more pr
13、edictable environments.Population GrowthlIt is useful to study population growth in an idealized situation in order to understand the capacity of species for increase and the conditions that may facilitate this type of growth.Population GrowthlIf immigration and emigration are ignored,a populations
14、growth rate equals birth rate minus death rate.Population GrowthlZero population growth occurs when the birth rate equals the death rate.lThe population growth equation can be expressed as:dNdt rNExponential GrowthlExponential population growth is population increase under idealized conditions.lUnli
15、mited resources.lUnder these conditions,the rate of reproduction is at its maximum,called the intrinsic rate of increase(rmax).Exponential GrowthlThe equation of exponential population growth is:dNdt rmaxNExponential GrowthlExponential population growth results in a J-shaped curve.Exponential Growth
16、lThe J-shaped curve of exponential growth is characteristic of some populations that are rebounding.Exponential GrowthlThe global human population has been in exponential growth for a long time.lAt what point will we surpass the carrying capacity for our planet?Logistic GrowthlExponential growth can
17、not be sustained for long in any population.lDepends on unlimited resources.lIn reality,there are one or more limiting resources that prevent exponential growth.Logistic GrowthlA more realistic population model limits growth by incorporating carrying capacity.lCarrying capacity(K)is the maximum popu
18、lation size the environment can support.The Logistic Growth ModellIn the logistic growth model,the per capita rate of increase declines as carrying capacity is reached.The Logistic Growth ModellThe logistic growth equation includes K,the carrying capacity.dNdt(K N)KrmaxNThe Logistic Growth ModellThe
19、 logistic model of population growth produces an S-shaped curve.The Logistic Model and Real PopulationslThe growth of laboratory populations of Paramecia fits an S-shaped curve.The Logistic Model and Real PopulationslSome populations overshoot K before settling down to a relatively stable density.Th
20、e Logistic Model and Real PopulationslSome populations fluctuate greatly around K.The Logistic Model and Real PopulationslThe logistic model fits few real populations,but is useful for estimating possible growth.The Logistic Model and Life HistorieslLife history traits favored by natural selection m
21、ay vary with population density and environmental conditions.K and r SelectionlK-selection,or density-dependent selection,selects for life history traits that are sensitive to population density.lFew,but larger offspring,parental care.lr-selection,or density-independent selection,selects for life hi
22、story traits that maximize reproduction.lMany small offspring,no parental care.Extrinsic Limits to GrowthlWhat environmental factors stop a population from growing?lWhy do some populations show radical fluctuations in size over time,while others remain stable?Extrinsic Limits to GrowthlAbiotic limit
23、ing factors such as a storm or a fire are density-independent their effect does not change with population density.lBiotic factors such as competition or predation or parasitism act in a density-dependent way the effect does change with population density.Community EcologylCommunity ecology examines
24、 the interactions among the various populations in a community.InteractionslPopulations of animals that form a community can interact in various ways.lBeneficial for one,negative for the otherlPredation,Parasitism,HerbivoryInteractionslBeneficial for one,neutral for the otherlCommensalismlBarnacles
25、growing on whalesInteractionslBeneficial for bothlMutualismInteractionslCompetition is a type of interaction that has a negative effect on both.lCommunity structure is often shaped by competition.lAmensalism occurs when only one of the competitors incurs a cost.lBalanus&Chthamalus barnaclesCompetiti
26、on and Character DisplacementlCompetition occurs when two or more species share a limiting resource.Competition and Character DisplacementlCompetition is reduced by reducing the overlap in their niches(the portion of resources shared).lThe principle of competitive exclusion suggests that organisms w
27、ith exactly the same niche cant co-occur.lOne will drive the other out.Competition and Character DisplacementlCharacter displacement occurs when the species partition the resource,using different parts of it.lAppears as differences in morphology.Competition and Character DisplacementlSpecies that ex
28、ploit a resource in a similar way form a guild.lSeed eaters vs.insect eaters.lA resource(insects)can be partitioned in terms of what part of the tree is searched.Predator-Prey CycleslMany populations undergo regular boom-and-bust cycles.lThese cycles are influenced by complex interactions between bi
29、otic and abiotic factors.PredationlPredation refers to an interaction where one species,the predator,kills and eats the other,the prey.lFeeding adaptations of predators include:claws,teeth,fangs,stingers,and poison.lAnimals also display a great variety of defensive adaptations.Cryptic ColorationlCry
30、ptic coloration,or camouflage makes prey difficult to spot.Aposematic ColorationlAposematic coloration warns predators to stay away from prey.MimicrylIn some cases,one prey species may gain significant protection by mimicking the appearance of another.Batesian MimicrylIn Batesian mimicry,a palatable
31、 or harmless species mimics an unpalatable or harmful model.Mllerian MimicrylIn Mllerian mimicry,two or more unpalatable species resemble each other.Species with a Large ImpactlCertain species have an especially large impact on the structure of entire communities either because they are highly abund
32、ant or because they play a pivotal role in community dynamics.Keystone SpecieslKeystone species are not necessarily abundant in a community.lThey exert strong control on a community by their ecological roles,or niches.Keystone SpecieslField studies of sea stars exhibit their role as a keystone speci
33、es in intertidal communities.Keystone SpecieslObservation of sea otter populations and their predation shows the effect the otters have on ocean communities.EcosystemslAn ecosystem consists of all the organisms living in a community as well as all the abiotic factors with which they interact.Ecosyst
34、emslEcosystems can range from a microcosm,such as an aquarium to a large area such as a lake or forest.EcosystemslRegardless of an ecosystems size,its dynamics involve two main processes:lEnergy flowlChemical cyclinglEnergy flows through ecosystems,while matter cycles within them.Trophic Relationshi
35、pslEnergy and nutrients pass from primary producers(autotrophs)to primary consumers(herbivores)and then to secondary consumers(carnivores).Trophic LevelslPrimary production in an ecosystem is the amount of light energy converted to chemical energy by autotrophs during a given time period.lPhotosynth
36、esisTrophic LevelslConsumers include:lHerbivores animals that eat plants.lCarnivores animals that eat other animals.lDecomposers feed on dead organic matter.Trophic LevelslDecomposition connects all trophic levels.lDetritivores,mainly bacteria and fungi,recycle essential chemical elements by decompo
37、sing organic material and returning elements to inorganic reservoirs.Energy FlowlEnergy flows through an ecosystem entering as light and exiting as heat.Gross and Net Primary ProductionlTotal primary production in an ecosystem is known as that ecosystems gross primary production(GPP).lNet primary pr
38、oduction(NPP)is equal to GPP minus the energy used by the primary producers for respiration.lOnly NPP is available to consumers.Energy TransferlThe secondary production of an ecosystem is the amount of chemical energy in consumers food that is converted to their own new biomass during a given period
39、 of time.Trophic Efficiency and Ecological PyramidslTrophic efficiency is the percentage of production transferred from one trophic level to the next.lUsually ranges from 5%to 20%.Pyramids of ProductionlThis loss of energy with each transfer in a food chain can be represented by a pyramid of net pro
40、duction.lA pyramid of numbers represents the number of individual organisms in each trophic level.Pyramids of BiomasslMost biomass pyramids show a sharp decrease at successively higher trophic levels.lOccasionally invertedNutrient CyclinglLife on Earth depends on the recycling of essential chemical
41、elements.lNutrient circuits that cycle matter through an ecosystem involve both biotic and abiotic components and are often called biogeochemical cycles.Toxins in the EnvironmentlHumans release an immense variety of toxic chemicals including thousands of synthetics previously unknown to nature.lOne
42、of the reasons such toxins are so harmful,is that they become more concentrated in successive trophic levels of a food web.Toxins in the EnvironmentlIn biological magnification,toxins concentrate at higher trophic levels because at these levels biomass tends to be lower.The Three Levels of Biodivers
43、itylGenetic diversity comprises:lThe genetic variation within a population.lThe genetic variation between populations.lSpecies diversity is the variety of species in an ecosystem or throughout the biosphere.lEcosystem diversity identifies the variety of ecosystems in the biosphere.Endangered Species
44、lAn endangered species is one that is in danger of becoming extinct throughout its range.lThreatened species are those that are considered likely to become endangered in the foreseeable future.Ecosystem ServiceslEcosystem services encompass all the processes through which natural ecosystems and the
45、species they contain help sustain human life on Earth.lPurification of air and water.lDetoxification and decomposition of wastes.lCycling of nutrients.lModeration of weather extremes.lAnd many others.Four Major Threats to BiodiversitylMost species loss can be traced to four major threats:lHabitat de
46、structionlIntroduced specieslOverexploitationlDisruption of“interaction networks”ExtinctionlHabitat fragmentation increases local extinction and speciation.lSpecies that have larger ranges or better dispersal abilities are better protected from extinction.ExtinctionlThere have been five mass extinctions.lEach time a large percentage of the species on earth went extinct.