23.4 Succession Flashcards
Succession
Process by which ecosystems change over time
2 types of succession
Primary
Secondary
Primary succession
Occurs on newly formed land or bare rock
No soil or organic material to begin with
Secondary succession
Occurs where soil is present but with no plant or animal species
Eg bare Earth after forest fires
When does primary succession occur?
Volcanoes erupt, releasing lava that forms igneous rock
Sand blown by the wind to form dunes
Silt and mud deposited at river estuaries
Glaciers retreat, depositing rubble and exposing rock
Seral stage
A step in the process of succession
At each stage, there is a change in abiotic factors (especially the soil)
Main seral stages
Pioneer community
Intermediate community
Climax community
Which is faster - primary or secondary succession?
Secondary succession
Pioneer community
Pioneer species arrive as spores or seeds carried by the wind by droppings of birds or animals
Adaptations of pioneer species
Can produce a large amount of spores and seeds
Seeds germinate rapidly
Can photosynthesise to produce their own energy
Can tolerate extreme environments
Can fix nitrogen from the atmosphere
Intermediate community
Weathering of bare rock produces particles that form the basis of soil
When pioneer species decompose, humus is formed
Soil can now support growth of new organisms
Eg of pioneer species
Lichen
Eg of secondary colonisers
Mosses
Eg of tertiary colonisers
Ferns
Adaptations of tertiary colonisers
Waxy cuticle to prevent against water loss
Can survive without abundance of water but absorb nutrients from soil
Climax community
Final seral stage
Community is in a stable state and shows very little change over time
Biodiversity in a climax community
Not usually the most diverse
Highest diversity in mid succession
Biodiversity decreases due to dominant species outcompeting pioneer and other species, causing elimination
Animal succession
Primary consumers (worms, insects) first colonise an area Secondary consumers arrive once a suitable food source has been established and existing plant cover provides suitable habitats
Which is faster - animal or plant succession?
Plant
Animal succession takes longer, especially land is geographically isolated
Plagioclimax
When succession is stopped artificially, the final stage formed
Ways of halting succession
Grazing and trampling of vegetation by domesticated animals - areas remain as grassland
Removing existing vegetation to plant crops - crops become final community
Burning to clear forest - increase biodiversity due to ash
