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life processes in the biosphere (ecological succession (the process of…
life processes in the biosphere
ecological succession
stages in the sequence of events that follows are called seres
water - hydrosere
bare rock - lithosere
sand - psammosere
the process of changes in a sere is called ecological succession and includes the following stages
the first living organisms to colonise must be adapted to abiotic conditions which are more extreme than later on when the habitat will support a higher biomass
the first organisms ton colonise are called
pioneer species
as time passes and populations increase, the pioneer species change the habitat and make it suitable for species that were not able to survive before - new colonisers may make pioneer species extinct
the new colonisers change the conditions making the habitat suitable for colonisation for new species
as abiotic factors become less extreme, survival depends on biotic factors and inter-species relationships
the squence of new species colonising and dying out continues until a final community of species develop which remain dominant as long as the climate does not change - this is called the
climax community
hydrosere
when an area of freshwater is created it is usually quickly colonised by single celled algae from the soil
birds and flying insects can bring in spores and seeds of algae
lake edges colonised by root plants
more the area is colonised by plants = the more food & shelter = more animals
as plants grow and die = lake fills with dead organic matter and sedimentation
emergent plants
sediment = less aquatic animals = bigger trees
transpiration by trees remove water and more sediments accumulate the soil becomes drier = oak trees colonise
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lithosere
development of a community of species on bare rock, created by a cliff fall, the retreat of a glacier or a volcanic eruption = lithosere
initial abiotic conditions = very harsh and unsuitable for most organisms
temperature = extreme - water availability = limited - no soil
lichens and algae first to colonise
conditions improve as dead organic matter and rock fragments build up
grasses and ferns
plants get larger as increase soil - conditions improve
pollination insects = flowering plants colonise = pollination
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psammosere
ecological succession that starts on sand
no plant nutrients - rapid drainage = poor water supplies- roots hard to form because of moving sand
more plants = stable sand = organic matter increases = more water
chapter 3