生态学(英文版)Ecology (生態學)IntroductionEcology -- __________________________________________________________Concept of the ecosystem - The biosphere and biomes•Bioshpere 生物圈o The part of the Earth and its atmosphere inhabited by life is called biosphereo Thus, the oceans, land surface and lower parts of the atmosphere all form parts of the biosphere.•Biome 生物群落o The biosphere can be divided into biomes which are linked by a common type of vegetation.o Forests, deserts and grasslands are the examples of biomes. Each biome consists of many ecosystems in which communities have adapted to differences in climate, soil, and other environmental factors throughout the biome.A. The Ecosystem生態系統An ecosystem is defined as a complex formed by the living community of different species interacting with one another and with their non-living environment of matter and energy to result in a stable and self-sustainable system.Components of an ecosystem : living community and non-living component• A population 種群consists of all members of the same species occupying a given area at the same time.• A community 群落consists of Populations of all the different species interacting with one another• A habitat 生境is a small specific place where an organism lives.- types of habitats :terrestrial habitat ---- forest, ___________________aquatic habitat ---- fresh water : pond, lake, reservoir, __________ •marine : sandy shore, muddy shore, ___________________A habitat can divide into numerous microhabitats小生境, eachwith_____________________________________________________________________________________•The niche生態位of a species describes the role of specific species in its community.Niches are sometimes distinguished from habitats by saying that the habitat of anorganism is its address, while its niche is its role in the community.e.g. on a tree : caterpillars (feed on leaves),beetles (burrow into trunk)they live on same place but functionally they occupy different niches.•The biotic (living) factors生物的are comprised by all living organisms within the ecosystem.•The abiotic (non-living) 非生物的factors are mainly divided into soil, water and climate.o Water is essential for all living organisms in the soil and enters living cells by osmosis.o Soils vary in their content of clay, silt, sand and gravel. The composition of soil determines the soil texture, porosity, water-retaining capacity and oxygen content.Soil contains a mixture of organic and inorganic nutrients (humus and minerals).o Climate includes environmental variables such as light, temperature, moisture, salinity and wind. These factors are important in determining the types of livingorganisms in the ecosystem.B. Energy flow and nutrient cycling in the ecosystemI) Transfer of energy (many approaches, according to functions in ecosystem)Food chainA linear sequence of organisms showing a pathway of food consumption from producers through a series of consumers. In this series, an organism feeds on the one before it and forms the food of the organism after it.Food chains are short (4-5 levels) because only 10 - 20 % of energy is transferred to the next stage.Each stage in food chain = _______________Trophic levels•The number of steps by which the organisms obtain their energy from plants in a food chain. --- the producers always at the first trophic level.______ consumers ______consumersa) Producers : autotrophs自養-- photosynthetic e.g. green plant, photosynthetic bacteria,chemosynthetic bacteria e.g. nitrifying bacteria,base of food chain and food web.N.B. : Phytoplanktons, which are microorganisms, are important producers floating on the upper layers of lakes or ocean. They are unicellularorganisms which also contain chloroplasts to carry out photosynthesisjust like the terrestrial plants .b) Primary consumers : herbivores which feed on plants e.g. pond snails, insect larvae.c) Secondary consumers : carnivores which feed on primary consumers e.g. small fish.d) Tertiary consumers : larger carnivores which feed on secondary consumers e.g. large fishe) Decomposers : mainly ________________________,分解者decompose dead bodies of plants and animals into simpler compoundswhich can then be absorbed by green plants again,important in recycling of nutrients and clearing up dead bodies andexcretory remains.f) Detritivores : consume the losses from the food chain, or dead organic matter detached食腐質動物from dead bodies or excreta (detritus), movement of energy and matter in a continuous manner, therefore hard to define trophic level,mainly bacteria, fungi, protozoans, insects, mites and some smallvertebrates,detritus detritivores carnivores and herbivoresImportances :⏹detritivores break down complex compounds to simpler molecules, therefore speedingup decomposition of dead bodies and excretory remains by breaking up detritus into small pieces thus increasing the surface area available for microbial action,⏹adding proteins and microorganisms onto the soil by their faecesg) other definition system :Producer herbivores carnivores top carnivores(prey) (prey/predator) (predator)Some animals may act as both herbivore and carnivore : omnivoreFood web- 2 or more interconnecting food chains, each organism may have different trophic levels營養層in different food chain within a food web.- examples of woodland and fresh water habitat (refer to any textbook)Example of food web : MarshII) Level of organizationArrange the following ecological terms in order :biosphere, community, population, organ, organism, biome, cellSpecies : ______________________________________________________________ ______________________________________________________________________III) Ecological energeticsProduction : amount of materials which accumulate over a fixed amount of time.Top carnivoresCarnivoresdecomposersHerbivoresGreen plantsN.B. Much of the solar energy reaching the plant is lost by reflection and photosynthetic inefficiency.Useful terms :•Biological productivity生物生產力is the rate at which biomass is produced by an ecosystem. It has two components:o Primary productivity初級生產力, the production of new organic matter by green plants (autotrophs).o Secondary productivity次級生產力, the production of new organic matter by consumers (heterotrophs).•Both of these can be divided into gross primary productivity and net primary productivity.•Gross primary productivity (GPP) 總初級生產力o The total amount of orgainc matter produced by green plants in unit area and per unit time. GPP does not represent the actual amount of food potentially available to heterotrophs because some of the organic matters are used to meet plant'srespiration and metabolism.•Net primary productivity (NPP) 淨初級生產力o The total amount of organic matter of the organism after respiration and metabolism have been fueled. Therefore it represents the potential food energyavailable to heterotrophs.Net secondary productivity : ____________________________________________N.B. : Usually, plant has 10% average efficiency of energy transfer while animal has 20%, explain why ?IV) Pyramids1) Pyramid of number (abundance) 數目塔- a diagram representing the progressive drop in numbers of individuals at each successive trophic level, usually upright e.g.- sometimes may be inverted e.g.- Not a good representation : ___________________________________________2) Pyramid of biomass (unit :g/m2) 生物量塔- Biomass ? _____________________________________________________________- better idea about the quantity of materials in each trophic level required to support those levelabove it, total amount of organic matter is largest at the base of a food chain,- normal shape : upright,rare case : inverted, why ?Reason ---- producer level has rapid turnover rate e.g. phytoplanktons may have smaller biomass than true but have higher productivity, therefore in this case,harvest animal is better than harvest producer,3) Pyramid of energy 能量塔(productivity) (Unit : g/m2/day, month, year)- the best because :a) it takes into account the rate of production, that is the time factor.b) no inverted pyramid --- always upright,c) importance of solar energy can be stressed.Criticism of all pyramids :- in a food web, many organisms cannot be placed in ONE suitable trophic level.- some still inverted, why ??Cycling of Nutrients in EcosystemsA. Carbon Cycle•Carbon is an essential building element for all organic compounds. The cyclic flow of carbon in Nature is known as the carbon cycle.o In Nature, the most abundant source of carbon exists as carbon dioxide free in the atmosphere and dissolve in oceans.o During photosynthesis, producers make use of light energy to convert carbon dioxide into organic carbon compounds in their bodieso When producers are eaten, the organic carbon compounds in their bodies are passed on to the consumers.o In the bodies of both producers and consumers, part of the organic carbon compounds is broken down into carbon dioxide during respiration and bringback to the atmosphere and oceans.o When the organisms die, a certain amount of organic carbon compounds is locked up in the dead bodies.o Generally the dead bodies undergo decomposition. The organic carbon compounds are converted to carbon dioxide and liberated during therespiration of decomposers.o Sometimes, the dead bodies may become fossil fuels. In such a case, the carbon dioxide can only be released when the fuels are burnt. The process iscalled combustion.Carbon CycleB. Nitrogen Cycle•Nitrogen is an essential element in the synthesis of proteins. The cyclic flow of nitrogen in Nature is known as the nitrogen.o During a process called nitrogen fixation, atmospheric nitrogen is changed to nitrates in the soil.This process is carried out by a group of bacteria callednitrogen-fixing bacteria.固氮細菌o During lightening閃電, atmospheric nitrogen can also be changed to nitrates.o The nitrogen in the soil is absorbed by producers in ionic forms and converted to organic nitrogenous compounds in their body.o When producers are eaten, the organic nitrogenous compounds in their bodies are passed on to the consumers.o Some of the nitrogen in the consumers' bodies are lost as excretory products.o When the organisms die, a certain amount of organic nitrogen is locked up in the dead bodies.o The organic nitrogen in the excretory products and dead bodies is broken down into ammonium compounds by a group of bacteria called putrefyingbacteria. The process is called putrefaction. 腐敗作用o The ammonium compounds are changed stepwise to nitrates by nitrifying bacteria. The process is called nitrification.o A process called denitrification changes some of the inorganic nitrogen compounds in the soil changed to nitrogen gas by the so-called denitrifyingbacteria. The nitrogen gas is returned to the atmosphere.Nitrogen cycleReference : Chinese version of Carbon and Nitrogen cycle Carbon Cycle :Nitrogen Cycle :Interdependence of organismsBasic interaction types0 no reaction + positive influence : benefit - negativea) + 0 :b) + + :c) + - :d) + - :e) - - :A) Positive interactions1) Commensalism 片行共生Different species of organisms living together, with only one getting benefits while the other get no harm, e.g. the barnacles藤壺attach themselves to the shells of hermit crabs. They obtain nourishment from the food left by the crab after it has eaten, and the crab can help them escape from danger.2) Mutualism (symbiosis) 互利共生Different species living together that are beneficial to both, e.g. lichens which are the association of fungi and algae. The alga is protected from high light intensity anddesiccation by the fungi. Moreover, the fungi are constantly supplied with organic food substances by the algae from photosynthesis.Other example : symbiotic bacteria and rabbits.B) Negative interaction1) Predation (+ -) :two individuals in which one preys on the other while the other is being eaten e.g. foxes and rabbits.N.B. predators regulating the prey population, i.e. Biological control, therefore benefically.2) Parasitism (+ -) :The parasite obtains food or shelter from the host. It can be further divided intoectoparasites, which live on the outer surface of a host, and endoparasites, which live within a host.e.g. tapeworm found in human digestive system obtain nourishment from the humanhost. N.B. the parasite must not kill the host or else it destroys itself.3) Competition (- -) :a) Interspecific or intraspecific :which one is more serious ? ________________________e.g. barnacles and oysters ---- compete for space and foodb) Two types :(Scramble爭奪) :(Contest) :c) Effects- on plant : changes in growth rate (competition for nutrients or light),extinction of less successful species,- on animal : i) aggression,ii) territory,iii) emigration,iv) increase in death rate,v) predation.d) Evolutionary significance :1) eliminate less well-adapted individuals, therefore gradual improvement of species,2) gives rise to adaptive radiationi.e. filling of more diverse ecological niches by an original species,therefore competition in field -- __________________________________________________________________________________________________3) success in competition depends on environmental conditions, conditions may favour one species at one time, and a different one at some other time, therefore different species may fluctuate in number.Succession 演替Succession is defined as a series of changes in the structure and composition of a community from the pioneer community to the climax community over a period of time.Primary succession :Invasion and colonization of bare rock, only algae andAccumulation of dead and decomposing organisms andfernsThe death and decomposition of these plants furtherenrich the soilColonization by seed-bearing plants, including grasses,shrubs and trees.Secondary succession :When the completely colonized surface has been influenced by living organisms (human) or environmental factors (fire), secondary succession occurs -- result in mesophytes dominantcauses of succession : changes in environment of a pondexisting communities no longer adaptednew species take overClimax community : 頂極群落The final stable and self-perpetuating community developed after number of successional communities, can resist environmental changes and competition, and it is the most productive community that the environment can sustain.Characteristics1) determined by habitat factors,2) interaction results in a stable balanced unit,3) a natural community : self sufficient and self-maintaining,4) species composition of a natural community is the result of natural selection.Adaptations of organisms to the environmenta) Definition :characteristic of an organism with definite value in allowing it to exist under condition of its habitats in order to ensure its continuity, allow the organism to make use of environmental resources or protect it against adverse conditions.b) Types of adaptation :a) morphological, b) physiological, c) behaviouralc) Significance of adaptation :- natural selection eliminates the one not adapted, therefore the adapted are favoured i.e.'survival of fittest',- ability of species to remain in existence depends on :i) ______________________________________________________________ii) ________________________________________________________________Examples of adaptationsReproductiona) Viviparous 胎生droppers of Kandelia水筆仔:- dominant in mangroves in H.K.,- seedlings (fruits) exhibit vivipary -- they develop while still attached to the parent plants, forming 'droppers' which fall into the water and float away, coming to rest in anupright position as the tide recedes,- therefore adapt to i) unstable substratum,ii) anaerobic mud,iii) saline condition.Survivala) Holdfast of Sargassum ( brown algae),- live on the intertidal zone of marine habitat,- develop a powerful holdfast which is a flattened disc capable of adhering strongly to almost any solid substratum.b) Shaped leaves of Pinus :- develop successfully as an evergreen plant in relatively poor, dry soil,- dark green 'needle' leaf with sunken stomata,- each has the shiny look associated with a thick cuticle and is grooved along its length,- small brown scale leaves for protection of buds and dwarfed shoot.Notes on field studiesEnvironment-the surroundings-i.e. the sum total of external influences acting on an organism or community.A) Abiotic (physical) : ----- climaticsoil (edaphic)topographica) ClimaticTemperature :- biochemical processes : most life exist within 0 – 600C- physiological effects (breeding),- adaptations :i) behavioral -----ii) structural -----Rainfall :- need for many functions (germination, locomotion, transport, metabolism, osmoregulation),- presence or absence of water causes many adaptations :in plants :in animals :-governs distribution of tropical rain forest, temperate forest,-Light :- three factors : ___________________________________- photosynthesis : food production,flowering (photoperiodism), transpiration,behaviour; breeding cycles,tropisms and nastic response,control zonationHumidity- is related to wind, rainfall and temperature,- transpiration rate,- behaviour of animals e.g. rocky shore animals seek damp place when exposed,Wind- transpiration,- affects mode of growth of vegetation :e.g. mechanical damage : stunting and shearing, defoliation, distortion- dispersal of seeds, fruits and spores, pollinationb) Soil (Edaphic) factors- soil factor i.e. factors which describe the conditions of the soil or substratum,- refer to notes of soil.c) Topographic factors- position of an area in relation to the surrounding country :i) altitude,ii) contour,iii) direction.B) Biotic factorsEffects1) Plant : source of food --- primary producer2) Interaction : refer to notes taught before3) Pollination and dispersal of seed and food by animals4) Protective adaptation :a) ____________ : protective coloration,b) ____________ : many animals resemble plants in shape e.g. stick insects or resembleother harmful animal species, therefore obtain benefits from thisresemblance.5) Man's effect on environment :- farming, pollution – important topic, discuss laterMethods of sampling on area : Study the distribution and abundance of organismsA) Transects 樣條Definition : a line cutting through an area, used to survey vegetation or fauna of the area.Types of transects1) Line transect 樣線:- linear survey of plants and animals through an area, change in level is not recorded.－select a typical stretch of areas of interest in the habitat,－laid a rope on ground, e.g. 10 meter (fixed at the 2 end),－check plants and animals touching the line every 0.5 – 1 meter,－record abundance and distribution of species touching the rope,－data graphed (histograms / kite diagrams / etc.) and analysed .2) Profile transects 剖面樣線:- a diagram shows the profile, i.e. change in level, along a given direction,- vegetation and animals are also indicated along it, show possible changes in vegetable type,- how to measure the level ?3) Belt transect 樣帶:- survey of a strip through an area, usually 2 parallel lines one metre apart,- usually record with quadrat.Presentation of data1)2)3)B) Quadrat樣方Definition : an square of known dimension, used to sample vegetation or animals, record theabundance and distribution of species recorded.The tool used : quadrat frame－random or along a transect (belt transect),－count the number of each species occurring in the quadrat / estimate the percentage coverage of each species in the quadrat,－for random sampling : repeat a number of times to get the average,－for systematic sampling : belt transect --- repeat along the transect,－Present the data (1)May be used to measure1) seasonal change2) zonation3) population numberPoint quadrat : a method by which fine pointed wires are lowered onto the vegetation inside the quadrat to measure relative abundance. e.g. frequency of plant AZonation 成帶現象- characteristic distribution of organisms into zones or strata (vertical zonation e.g. forest).Discussion :What are the limitations of using transect and quadrat ?Example of habitat --- Rocky shore岩岸General layout :Factors on rocky shore1) tidal flow,2) wave action,3) substratum 基層,4) sunlight (illumination),5) rainfall, humidity,6) wind,7) salinity (rock pool)Problems faced1)2)3)4)General adaptation on rocky shoreUpper shore Lower shore1) lung breathers _____________________2) complex excretory organs and excretion by diffusion and excrete ammoniaexcrete uric acids3 mobile, cryptic, thick shells sedimentary, non-cryptic, thin Typical distribution of flora and fauna。