Unit 2 Ecosystems

Definitions of all key words.

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Community - All the organisms living in one easily defined area.

Habitat - The place where an organism lives.

Population - All the organism belonging to the same species living in the same area at the same time. Males and females within the population can inerbreed.

Niche - The role of the species in a comminity (position in the food chain and the intereactions it has with other species).

Ecosystem - A self - contained community together with all the physical features that influence the community. The interactions between orgainsms and their environment.

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Producer - An organism that converts simple inorganic molecules into complex organic compounds. Most use light to provide the energy to drive the reactions involved.

Consumer - An organism that gain energy from complex organic matter.

Decomposer - An organism that feeds on waste from other organisms, or on dead organisms.

Trophic Level - Each feeding leve in a food chain.

Primary Succession - The changes that result when the starting point is bare, uncolonised land. e.g. samd dunes, lava, lanslides, retreating glaciers.

Secondary Succession - when an established communtiy is destroyed and a new community develops.

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Climax Community - The final, stable community that results after succession. The species of a climax community:

- have large seeds(with large energy store) so seedling can survive low light intensity.

- have a specialised niche.

- are unable to tolerate great lfuctuations in water content of soil.

- are strongly influenced by other organisms.

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Pioneer Species - The early arrivals to a habitat experiencing succession:

- are able to tolerate extreme conditions.

- have very good means of dispersal, usually by wind.

- are not able to compete for resources.

- not influenced by or dependant on animal species.

- may be able to fix nitrogen and build up soil nutrients.

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Decomposers - organisms that feed on waste from other organisms or on dead organisms.

Nitrogen Fixation - The conversion of nitrogen gas into a form usable by plants, such as nitrate or ammonium ions.

Carrying capacity - the maximum population denisty that can be supported by permanantly in its habitat.

Density-dependant limiting factors have a proportional increase or decreases in their effect as the population density rises or falls.

Biotic - caused by other living things. e.g. predation of infection by pathogens.

Abiotic - inloving non-living components of the environment. e.g. water supply.

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Intraspecific Competition - between members of the same species.

Interspecific Competetion - between memebers of different species.

Competitive Exclusion - As a result of competition, 2 species will not occupy the same niche.  One will displace the other so each adopts a certain way of life in which it has an advantage.

Conservation - may be needed to protect a species, habitat or ecosystem because it is at risk from human influence or other pressures. Includes the active management needed to maintain or increase biodiveristy.

Preservation - protects species and/or habitats for example by creating a nature reserve.

Sustainable Management - allows an economically important resource to be exploited indefinatlely.  

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