One_Day

One day 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 the second organism in a food chain (in the second trophic level); consumes/ CONSUMER obtains energy from the producer; (thus a herbivore). SECONDARY consumes/obtains energy from the primary consumer; (thus a carnivore). CONSUMER PYRAMID OF a representation of the number of organisms in each trophic level in an NUMBERS ecosystem; the width of each block is proportional to the number of organisms in each trophic level. PYRAMID OF (better) a representation of the biomass in each trophic level in an ecosystem; the BIOMASS width of each block is proportional to the biomass in each trophic level. PYRAMID OF (better still) a representation of the energy in each trophic level in an ecosystem; ENERGY the width of each block in proportional to the energy in each trophic level; usually measured in KJ m.-2 year-1. CARRYING the maximum population that a particular environment can support. CAPACITY ENVIRONMENTAL the environmental factors which reduce population growth rate: e.g. disease RESISTANCE predation, competition. N.B. an example often gains a mark!