Ecology Definitions
ECOSYSTEM
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.
ENVIRONMENT
all the factors in a habitat which affect an organism; these may be either living
(= biotic) or non living (= abiotic).
POPULATION
all the members of one species in a habitat at one time.
COMMUNITY
all the organisms (= ∑ the biotic factors) in a particular habitat at one time.
HABITAT
the geographical area occupied by an ecosystem.
NICHE
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’).
SPECIES
a group of potentially interbreeding individuals; which do not normally interbreed
with other groups/species to produce viable, fertile offspring.
FOOD CHAIN
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.
FOOD WEB
all the interconnected food chains in an ecosystem (usually complex to calculate).
TROPHIC LEVEL
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.
PRODUCER
the first organism in a food chain; an autotroph (i.e capable of manufacturing
organic molecules/food, normally by photosynthesis (thus, normally a plant).
PRIMARY
CONSUMER
the second organism in a food chain (in the second trophic level); consumes/
obtains energy from the producer; (thus a herbivore).
SECONDARY
CONSUMER
consumes/obtains energy from the primary consumer; (thus a carnivore).
PYRAMID OF
NUMBERS
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.
PYRAMID OF
BIOMASS
(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.
PYRAMID OF
ENERGY
(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.
CARRYING
CAPACITY
the maximum population that a particular environment can support.
ENVIRONMENTAL the environmental factors which reduce population growth rate: e.g. disease
RESISTANCE
predation, competition.
N.B. an example often gains a mark!