生态学英文版

1、Ecology P.19Ecology （生!W 擘）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

2、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 throu

3、ghout the biome.A. The Ecosystem 生Ii系统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

4、community and non-living component? A population 槿群 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.-

5、types of habitats :terrestrial habitat - forest, aquatic habitat fresh water : pond, lake, reservoir,?marine : sandy shore, muddy shore,A habitat can divide into numerousmicrohabitats /、生境,each with? The niche 生魅位 of a species describes the role of specific species in its community. Niches are somet

6、imes distinguished from habitats by saying thah e habitat of an organism 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)

7、 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, sa

8、nd 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 win

9、d. These factors are important in determining the types of living organisms in the ecosystemB. 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 f

10、rom 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

11、 steps by which the organisms obtain their energy from plants in a food chain. - the producers always at the first trophic level.Producersconsumersconsumers consumersdecomposersa) Producers : autotrophs 自U - photosynthetic e.g. green plant, photosynthetic bacteria, chemosynthetic bacteria e.g. nitri

12、fying 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 unicellular organisms which also contain chloroplasts to carry out photosynthesis just like the terrestrial plants .b) Prim

13、ary 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 bo

14、dies of plants and animals into simpler compounds which can then be absorbed by green plants again,important in recycling of nutrients and clearing up dead bodies and excretory remains.f) Detritivores : consume the losses from the food chain, or dead organic matter detached 食腐®CS& 物from dea

15、d bodies or excreta (detritus), movement of energy and matter in acontinuous manner, therefore hard to define trophic level,mainly bacteria, fungi, protozoans, insects, mites and some small vertebrates,detritusd detritivores c carnivores and herbivoresImportances :detritivores break down complex com

16、pounds to simpler molecules, therefore speeding up 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 :

17、Produceihherbivoresccarnivorestop carnivores(prey)(prey/predator) (predator)Some animals may act as both herbivore and carnivore : omnivoreAUTOTROPHHERBIWREPRIMfiRVPRIMARYPRODUCERCONSUMERPR I MARV CARN I MORE SECONDflRV CONSUMERSECONDARY CARNIUORE TERT IRRV CONSUrtERFood web-2 or more interconnectin

18、g food chains, each organism may have different trophic leve管看屈 in different food chain within a food web.-examples of woodland and fresh water habitat (refer to any textbook)Example of food web : MarshKiller UJhaleMarsh Uegetation (includes miany speciesof sedges, grasses, bullrushes, algaeT etcjII

19、) 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 pl

20、antsN.B. Much of the solar energy reaching the plant is lost by reflection and photosynthetic inefficiency.Useful terms :? Biological productivity 生物生 力 is the rate at which biomass is produced by an ecosystem. It has two components:o Primary productivity 初级生力,the production of new organic matter by

21、 green plants (autotrophs).o Secondary productivity 次级生力,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)余恩初级生 力o The total amount of orgainc matter produced

22、 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's respiration and metabolism.? Net primary productivity (NPP)浮初级生 力o The total amount of organic matt

23、er of the organism after respiration and metabolism have been fueled. Therefore it represents the potential food energy available 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

24、 of number (abundance) 数目塔- 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 ma

25、terials in each trophic level required to support those level above 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 b

26、ut 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 theime factor.b) no inverted pyramid - always upright,c

27、) 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 c

28、yclic flow of carbon in Nature is known as thecarbon cycle.o In Nature, the most abundant source of carbon exists asarbon 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

29、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 duringrespiration and bring back to the atmosphere and oceans.o When

30、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 threspiration of decomposers.o Sometimes, the dead bodies may becomfoss

31、il fuels. In such a case, the carbon dioxide can only be released when the fuels are burnt. The process is called combustion.Carbon CycleDecomposition / jn the atmosphere*and difisoh/edCoiTibusticnDeathExcretion/deathRespirationDeath： but decay is preventedDeath, but decay isPlantsB. Nitrogen Cycle?

32、 Nitrogen is an essential element in thesynthesis of proteins. The cyclic flow of nitrogen in Nature is known as the nitrogen.o During a process callednitrogen fixation , atmospheric nitrogen is changed to nitrates in the soil.This process is carried out by a group of bacteria callednitrogen-fixing

33、bacteria .固氮余田菌o During lightening , 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

34、passed on to the consumers.o Some of the nitrogen in the consumers' bodies are lost aesxcretory 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 co

35、mpoundsby a group of bacteria calledputrefying bacteria. Theprocess is calledputrefaction . 腐败作用o The ammonium compounds are changed stepwise to nitrates bnyitrifying bacteria . The process is callednitrification .o A process calleddenitrification changes some of the inorganic nitrogen compounds in

36、the soil changed to nitrogen gas by the so-calleddenitrifying bacteria. The nitrogen gas is returned to the atmosphere.Nitrites (NOJhtitriring badenae.g. NdrobacterAb5o option 口rocia"怕的巾S piianUNidify ngbaclerlaQ.g. N市gGEcnasNlirogan / fixing b£cteiiaDenilrlfyingbacteriae.g. Pseifdcgn醺5:君忘

37、 Phizobdin (symbiallcj J F启电dingd&nitriticans : Azotoict6r (hee-hving) ; and-/: dtgestnUghtnng XJ 3 .Ammaniunionmp&unds(HI：AtmosphericnitrogenPretflinih$ animalsChorrtolGominalior)Industrial (Haber)piocessPulrefyng bacteriaDeathF .irefying bnctenatxcrtilionReference : Chinese version of Carb

38、on and Nitrogen cycleCarbon Cycle :Nitrogen cycleNitrogen Cycle :硝化iffl菌，例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 toget

39、her, with only one getting benefits while the other get no harm, e.g. the barnacles 藤 1ft 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

40、species living together that are beneficial to both, e.gl.ichens which are the association of fungi and algae. The alga is protected from high light intensity and desiccation by the fungi. Moreover, the fungi are constantly supplied with organic food substances by the algae from photosynthesis.Other

41、 example : symbiotic bacteria and rabbits.B) Negative interaction1) Predation (+ -) :two individuals in which one preys on the other while the other is being eatene.g. foxes and rabbits.N.B. predators regulating the prey population, i.e. Biological control, therefore benefically.2) Parasitism (+ -)

42、:The parasite obtains food or shelter from the host. It can be further divided into ectoparasites, 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 human host. N.B. the parasite must not k

43、ill 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 孚 U):(Contest) :c) Effects- on plant : changes in growth rate (competition for nutrients or light)

44、, 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 radiation1 .e. fillin

45、g 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.Succe

46、ssion 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 and lichens can invade and colonize the area(insufficie

47、nt soil and nutrients for trees and shrubs)- first colonizers.Accumulation of dead and decomposing organisms and the erosion of rock by weatheringColonization by larger plant species such as mosses or fernszThe death and decomposition of these plants further enrich the soil7Colonization by seed-bear

48、ing plants, including grasses, shrubs and trees.Secondary succession :When the completely colonized surface has been influenced by living organismsipman) or environmental factors fire), secondary succession occurs - result in mesophytes dominantcauses of succession : changes in environment of a pond

49、Iexisting communities no longer adaptedInew species take overClimax community : IB趣群落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

50、 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) Defin

51、ition :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) physiolo

52、gical, 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

53、 Kandelia 水肇仔:- 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 an upright position as the tide recedes,- therefore adapt to i) unstabl

54、e substratum,11) 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 oPinus :- develop s

55、uccessfully 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 studiesEn

56、vironment- 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) be

57、havioral 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. r