Communities Flashcards
what is the definition of a community?
-the sum of all the total populations in a particular area
-it is the biotic component of an ecosystem involving interactions between the autotrophic and heterotrophic populations
what does the term ecosystem mean?
-the community plus its physical environment which consists of both biotic and abiotic components
is it the biotic or abiotic components which decide the type of population which develops?
abiotic components e.g. rock type and climate
what does succession mean? what are the two components involved in succession?
-the term used to describe the changes over time in ecosystems
-the abiotic environment and the community
where does primary succession occur?
-on newly formed barren substrates which have not previously been colonised
what is the first stage of succession involve?
-the appearance of colonising pioneer species e.g. lichens, which are able to survive in hostile conditions
-this then will begin to degrade the rock forming embryonic soil
-the lichens will then begin to die and decompose meaning the soil will be at the stage where it can support mosses
what are the next stages of succession after the lichens die and the embryonic soil is formed?
-through time the soil depth and fertility will increase and the number of plant species increase
-despite plant biodiversity decreasing again as succession approaches maturity
-plant biomass also increases
-each stage in succession is called a sere and after a certain amount of these the climax community develops e.g. large trees
-diversity can reduce because of this species as few species can survive with low light levels on the woodland floor
what is the definition of climax community?
-the stable end stage of succession which is in equilibrium with the environment
what is each stage of succession known as?
-a sere
what are the two factors which can influence the development of the climax community?
-the climate climax and the biotic climax
what are the 6 factors which all primary successors have in common?
-they are predictable in pattern
-the abiotic environment becomes less hostile
-the height and biomass of vegetation increases
-communities become more complex
-increased biodiversity
-later stages of succession will be more stable than the initial seres
what is secondary succession? when does it occur?
-it does not start with the pioneer species as the embryonic soil already has been developed
-it starts with this soil which will contain seeds from many species as well as other plant parts which can rapidly regenerate
-it occurs when the climax community has been destroyed from fire or weather conditions
which type of succession is quicker?
-secondary succession
