Succession-primary and secondary

1. 6.2 Ecological6.2 Ecological
SuccessionSuccession
OrOr
How to be “successful” in natureHow to be “successful” in nature

2. Nothing is constant but changeNothing is constant but change
 Organisms affect the environment as much as theOrganisms affect the environment as much as the
environment affects them-plants make soil,environment affects them-plants make soil,
trees growing create shade, man really changestrees growing create shade, man really changes
his environment (this is subject of the secondhis environment (this is subject of the second
semester) , fire destroys forests, also releasesemester) , fire destroys forests, also release
seedsseeds
As the environment changes, the communities in thatAs the environment changes, the communities in that
environment change-in many cases the sequence ofenvironment change-in many cases the sequence of
communities follow a definite pattern and this is whatcommunities follow a definite pattern and this is what
we mean by successionwe mean by succession

3. Primary SuccessionPrimary Succession
 This is the sequence of organisms that form or existThis is the sequence of organisms that form or exist
in an originally lifeless environmentin an originally lifeless environment
 This would occur after a volcanic eruption,This would occur after a volcanic eruption,
or the land after a glacier has retreatedor the land after a glacier has retreated
The first step is for colonization of new organisms andThe first step is for colonization of new organisms and
for soil to formfor soil to form
Lichen can live on bare rock, and often colonizes firstLichen can live on bare rock, and often colonizes first
and helps form soil ( organic matter and acid secretedand helps form soil ( organic matter and acid secreted
by the lichen help break down rock & form soil)by the lichen help break down rock & form soil)

4.  Lichen is known as aLichen is known as a pioneerpioneer communitycommunity
 Once soil is formed, grasses other small plantsOnce soil is formed, grasses other small plants
Can grow- seeds get there by wind, animalsCan grow- seeds get there by wind, animals
 Of course these plants create more soil, & break upOf course these plants create more soil, & break up
the rocks even more- eventually they push out thethe rocks even more- eventually they push out the
lichens- grasses take overlichens- grasses take over
 Soil gets deeper and more fertile- non-woody plantsSoil gets deeper and more fertile- non-woody plants
( shrubs ) can grow. At this point it has been several( shrubs ) can grow. At this point it has been several
generations and the ecosystem is susceptible togenerations and the ecosystem is susceptible to
drastic changes by any disturbancedrastic changes by any disturbance

5.  Eventually, trees can grow w/shallow roots-like pinesEventually, trees can grow w/shallow roots-like pines
 Now these trees shade out the grasses and shrubs, andNow these trees shade out the grasses and shrubs, and
the forest floor is changing because of the leaf litter,the forest floor is changing because of the leaf litter,
soil gets even deepersoil gets even deeper
 Now a hardwood forest- deciduous trees can takeNow a hardwood forest- deciduous trees can take
over- this is usually theover- this is usually the climax communityclimax community
 Climax communities are very stable- change noClimax communities are very stable- change no
further-highly diverse- can withstand even severefurther-highly diverse- can withstand even severe
local disturbanceslocal disturbances

6. Secondary SuccessionSecondary Succession
 Disturbances are not usually severe enough to destroyDisturbances are not usually severe enough to destroy
the soilthe soil
 Succession that occurs where a disturbance eliminatesSuccession that occurs where a disturbance eliminates
most organisms, but does not destroy the soil, ismost organisms, but does not destroy the soil, is
calledcalled secondary successionsecondary succession
 Examples of this are fires, human disturbances,Examples of this are fires, human disturbances,
 Secondary succession usually starts w/ the grassesSecondary succession usually starts w/ the grasses
and non-woody shrubs then works up to theand non-woody shrubs then works up to the
softwood, quick growing trees, then slow-growingsoftwood, quick growing trees, then slow-growing
hardwoodshardwoods

7. Sometimes a climax communitySometimes a climax community
never forms!never forms!
 Certain ecosystems never reach a climaxCertain ecosystems never reach a climax
community- grasslands. Fire often disruptscommunity- grasslands. Fire often disrupts
The pattern of succession and actually is anThe pattern of succession and actually is an
important part of the ecosystem.important part of the ecosystem.
Lodgepole pine forest- describeLodgepole pine forest- describe
Summary- lichen-grasses-shrubs-pines-harwoodsSummary- lichen-grasses-shrubs-pines-harwoods

8. AssignmentAssignment
 Go to the library and research your ecosystem-Go to the library and research your ecosystem-
find out the succession pattern. Describe what itfind out the succession pattern. Describe what it
isis
 Go to the library and find an example ofGo to the library and find an example of
2 symbiotic relationships in your ecosystem-2 symbiotic relationships in your ecosystem-
One parasitic and one of either commensalism orOne parasitic and one of either commensalism or
mutualismmutualism

9. Aquatic SuccessionAquatic Succession
 Clear, lifeless lakeClear, lifeless lake
 Water plants, reeds build up nutrientsWater plants, reeds build up nutrients
 Organic matter builds upOrganic matter builds up
 Water plants cover lakeWater plants cover lake
 MarshMarsh
 MeadowMeadow
 ForestForest

10. Island SuccessionIsland Succession
 Much like volcanic landMuch like volcanic land
 Organisms get there by wind, water, or otherOrganisms get there by wind, water, or other
organismsorganisms
 Often colonized by birdsOften colonized by birds
 Lots of opportunities for niches- initially veryLots of opportunities for niches- initially very
few organisms-no competition; organisms canfew organisms-no competition; organisms can
evolve to fill specific niches Tortoises onevolve to fill specific niches Tortoises on
Galapagos islands; birds w/ different beaksGalapagos islands; birds w/ different beaks
etc.etc.