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Biology (Unit 4) AQA…read more

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· Occurs on bare land
· Examples:
· Glacier retreating
· Volcanic eruption
· Sand piled onto dunes
· Mud deposits in estuaries A pioneer species must inhabit the bare land this species
· Rock face should:
· Produce vast quantities of seeds which can be dispersed
· Stages:
onto isolated land
· Lichens (pioneers)
· Moss · Rapidly germinate
· Ferns · Be able to photosynthesise
· Grass · Be able to fix nitrogen as there is a lack of nutrients on
· Shrubs new land
· Trees
· Be tolerant to extreme conditions…read more

Slide 3

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This type of succession occurs on
land that has previously been
Soil is already present along with
nutrients for growth.
The pioneer species may be
Examples of secondary succession:
larger plants such as shrubs as
the conditions are less hostile · Forest fires
than in primary succession.
· Tree felling areas
· Abandoned farmland
· Landfills
· Road sides…read more

Slide 4

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Conditions for the pioneer species.
In primary succession In secondary succession
· Hostile conditions · Soil layer present
· No soil to retain water · Containing some nutrients and water
· Little nutrients for growth · Some seeds remain
· Temperature may fluctuate more due · Shrubs and grass can inhabit as
to land being bare pioneer species due to conditions
· No shelter from wind or weather being less hostile
· Only spores and seeds can inhabit
due to hostile conditions…read more

Slide 5

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Common features of succession
· None living environments become less hostile (soil forms, more nutrients,
more shelter)
· Greater number and variety of habitats develop
· Increased biodiversity (diversity most in middle but decreases towards
climax due to dominant species outcompeting)
· More complex food webs therefore increased biomass.…read more

Slide 6

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Climatic Climax
· Caused by abiotic factors such as temperature, availability of water and
· E.g. In UK mild temperatures, water
is available therefore climax contains
large trees if deep soil is present.
· E.g. In polar climates, low temp,
not much water so shrubs will be the
climax as large trees can't grow.…read more

Slide 7

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