succession Flashcards
what is the defintion of succesion
the process in which species change their environment and are replaced by new species, over a period of time
what can an ecosystem be described as
dynamic and thus are constantly changing
what are the two types of succesion
primary
secondary
what is primary succession
the process of species colonising a new area on land that is newly formed/exposed
how is the primary succession new area created
-The magma from erupting volcanoes cools and often leads to the formation of new rock surfaces or even new rocky islands in the sea
-Another way new land can be exposed is by sea-level dropping or the drying up of a lake, leaving areas of bare rock
-also any barren terrian that is being colonised eg sand dunes with marram grass as the prisoner species
describe the process of primary success
- in the early stages the abiotic factors are the most important in determining which species can colonise - they need to be species that can tolerate a hostile abiotic environment **
-these species are called the pioneer species **
-as the pioneer species becomes established they can **change the habitat in ways that favour other species more strongly than themselves - eg when they die - organic matter forms
-this makes the habitiat less hostile** and abitoic factors become less important and **other speices **can surive and be established
-these species inturn change the enivronment which cause the species diversity to increase thus increasing the overall biodiversity
-the stability of the environment increases as there are less hostile conditions
-food webs become more complex and is less likely to be changed by changes in species
-as condtions change more species beocme established, some of the original species are lost
-eventually this continues until a climax community is reached - consiting of plants and animals enabling a greater food source and habitiat for animals
-there is often one dominant plant and animal speices so the **overall biodiversity decreases **as the dominant species will out-compete others
what are some features of pioneer species that make them suitable colonisers
-reproduce asexually- so can rapidly build up the pop
-wind-dispered seeds/ pores-easily reach isolated situations
-rapid germination of seeds on arrival - so dont require dormancy
-abilty to photosynthesise - light is normally avaliable but food is not - so there is no dependency on animals
-ability to find nitrogen from the atmos - thr soil has few nutirents to survive on
-tolerance to extreme conditions
give some features of succession
-non-living envrionment will become less hostile - soil forms and nutrients are more plentiful
-greater number and vairety of habitats and niches which in turn produce
-increased biodiveristy - that will peak in mid-succession and fall at the climas community
-more complexed food webs thus increasing biomass
what is secondary succession
takes place when life is already present but has been altered in some way
how does the speed of secondary succession vary to primary
secondary succesion happens much quicker as soil if often already present that may contain seeds that will germinate
what are the 3 main causes of secondary succession
-natural catastrophes that remove exisiting variation such as fires
-human desrtuction of climax communities for example the drainage of marshes or buring of forests
-human managament of habititas to maintain communties at an early successional stage eg mowing a lawn
what is the main dominat species in the uk
deciduous woodland
give an example of species at each stage of primary succession
bare rock
colinisation by lichens,weathering rock, production of dead organic material
growth of moss, further weathering, beginnings of soil formation
growth of small plants eg ferns,grasses, further improvement of soil
larger herbaceous plants can grow in the deeper more nutirent-rich soil
climax community dominated by shrubs and trees
pioneer community
earliest community that becomes established on a bare site
sere
alternative name for succession in a community
