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A Level Ecosystem Terms
Definitions for Ecosystem terms
18
Biology
12th Grade
03/29/2009

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Term
ECOSYSTEM
Definition
all the communities/living organisms/ biotic factors and environmental / abiotic factors in a particular area; these factors are interacting and interdependent; they make up a self-contained system which is self supporting in terms of energy flow.
Term
ENVIRONMENT
Definition
all the factors in a habitat which affect an organism; these may be either living (= biotic) or non living (= abiotic).
Term
POPULATION
Definition
all the members of one species in a habitat at one time.
Term
COMMUNITY
Definition
all the organisms (= ? the biotic factors) in a particular habitat at one time.
Term
HABITAT
Definition
the geographical area occupied by an ecosystem.
Term
NICHE
Definition
the role of a species within an ecosystem; its location/spatial habitat and functions - relationships/interactions with other organisms - and its effect on the environment. Two different species do not normally occupy exactly the same niche in the same habitat at the same time (= ‘competitive exclusion principle’).
Term
SPECIES
Definition
a group of potentially interbreeding individuals; which do not normally interbreed with other groups/species to produce viable, fertile offspring.
Term
FOOD CHAIN
Definition
a sequence of organisms in an ecosystem in which each is the food of the next organism in the sequence. Arrows represent energy flow through the chain.
Term
FOOD WEB
Definition
all the interconnected food chains in an ecosystem (usually complex to calculate).
Term
TROPHIC LEVEL
Definition
a feeding level in a food web - defined by the method of obtaining food; all the organisms in a particular trophic level are the same number of energy transfers away from the producers.
Term
PRODUCER
Definition
the first organism in a food chain; an autotroph (i.e capable of manufacturing organic molecules/food, normally by photosynthesis (thus, normally a plant).
Term
PRIMARY CONSUMER
Definition
the second organism in a food chain (in the second trophic level); consumes/obtains energy from the producer; (thus a herbivore).
Term
SECONDARY CONSUMER
Definition
consumes/obtains energy from the primary consumer; (thus a carnivore).
Term
PYRAMID OF NUMBERS
Definition
a representation of the number of organisms in each trophic level in an ecosystem; the width of each block is proportional to the number of organisms in each trophic level.
Term
PYRAMID OF BIOMASS
Definition
(better) a representation of the biomass in each trophic level in an ecosystem; the width of each block is proportional to the biomass in each trophic level.
Term
PYRAMID OF ENERGY
Definition
(better still) a representation of the energy in each trophic level in an ecosystem; the width of each block in proportional to the energy in each trophic level; usually measured in KJ m.-2 year-1.
Term
CARRYING CAPACITY
Definition
the maximum population that a particular environment can support.
Term
ENVIRONMENTAL RESISTANCE
Definition
the environmental factors which reduce population growth rate: e.g. disease, predation, competition.
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