Ecological succession describes how communities change over time through primary and secondary succession. Primary succession occurs in areas without soil, like new bare rock, where pioneer species establish and slowly transform the rock into soil over long periods. Secondary succession follows a disruption, like a forest fire, where the original community regrows through different stages. Mature communities tend to have greater biodiversity and are dominated by climax species well-adapted to the local environment. Cycles of matter, like carbon and nitrogen, are essential to life and involve exchanges between living things and their environment.

1. Ecological Succession &Ecological Succession &
Cycles of MatterCycles of Matter

2. ► Regrowth of a ForestRegrowth of a Forest
 Succession: replacement of one type ofSuccession: replacement of one type of
communitycommunity by another at a single place overby another at a single place over
a period of timea period of time

3.  Example: burned areas of YellowstoneExample: burned areas of Yellowstone
National Park started to regrow small,National Park started to regrow small,
green plants by the nextgreen plants by the next yearyear

4. ► Primary SuccessionPrimary Succession
 Small organisms start toSmall organisms start to
grow in areas wheregrow in areas where
other organisms had notother organisms had not
previouslypreviously livedlived
 No soil in this area, justNo soil in this area, just
bare rockbare rock
 Over long period of time,Over long period of time,
organisms live and dieorganisms live and die
on rock, and rock ison rock, and rock is
slowly transformed intoslowly transformed into
soilsoil

5.  FirstFirst organisms to live in an area are calledorganisms to live in an area are called pioneerpioneer
speciesspecies
 Example: slowly retreating glacier exposes new rockExample: slowly retreating glacier exposes new rock
over many years there is enough soil for mosses toover many years there is enough soil for mosses to
growgrow soil deepens and mosses are replaced bysoil deepens and mosses are replaced by
grassesgrasses and wildflowersand wildflowers

6. ►Secondary SuccessionSecondary Succession
 Sometimes, existing community is destroyed bySometimes, existing community is destroyed by
natural disastersnatural disasters, such as fire or flood, such as fire or flood
 If soil is left intact, the original community mayIf soil is left intact, the original community may
regrow through a series of stages calledregrow through a series of stages called
secondarysecondary successionsuccession
 Example: first year after farmer stops growingExample: first year after farmer stops growing
crops, weeds start to growcrops, weeds start to grow by second year,by second year,
new weed appearnew weed appear forests may form overforests may form over
many yearsmany years

8. ►Mature Communities and BiodiversityMature Communities and Biodiversity
 In early stages ofIn early stages of successionsuccession, only few, only few
species grow in an areaspecies grow in an area
 These species grow quickly and make manyThese species grow quickly and make many
seedsseeds that scatter easilythat scatter easily
 As community matures, it many beAs community matures, it many be
dominated by well-adapted,dominated by well-adapted, slow-growingslow-growing
climax speciesclimax species
 Variety of species that are present in anVariety of species that are present in an
area is referred to as biodiversityarea is referred to as biodiversity

9.  MatureMature
community maycommunity may
not always be anot always be a
forest; it simplyforest; it simply
has organismshas organisms
that are wellthat are well
adapted to liveadapted to live
together in thetogether in the
same area oversame area over
timetime

10. Cycles of MatterCycles of Matter
►Carbon CycleCarbon Cycle
 Exchange ofExchange of carboncarbon between the environmentbetween the environment
and living thingsand living things
 PhotosynthesisPhotosynthesis is the basis of carbon cycleis the basis of carbon cycle
 Carbon returns to the environment when sugarCarbon returns to the environment when sugar
molecules are broken down to release energy—molecules are broken down to release energy—
process is calledprocess is called respirationrespiration
 Carbon dioxideCarbon dioxide and water are released asand water are released as
byproducts of respirationbyproducts of respiration

12. ► Nitrogen CycleNitrogen Cycle
 OrganismsOrganisms
need nitrogenneed nitrogen
to buildto build
proteins andproteins and
DNA for newDNA for new
cellscells
 AboutAbout 78%78% ofof
Earth’sEarth’s
atmosphere isatmosphere is
nitrogen gasnitrogen gas

13.  Bacteria inBacteria in soilsoil changechange
nitrogen gas into formsnitrogen gas into forms
that plants can use—that plants can use—
process called nitrogenprocess called nitrogen
fixationfixation
 When organisms dies,When organisms dies,
decomposersdecomposers breakbreak
down remains anddown remains and
release form of nitrogenrelease form of nitrogen
into soil that plants caninto soil that plants can
useuse
 Certain types of bacteriaCertain types of bacteria
in soil convert nitrogenin soil convert nitrogen
into ainto a gasgas that returns tothat returns to
atmosphereatmosphere

15. ►Water CycleWater Cycle
 Movement of water between theMovement of water between the oceansoceans,,
atmosphere,atmosphere, landland, and living things, and living things
 During evaporation, sun’s heat causes waterDuring evaporation, sun’s heat causes water
to change from liquid toto change from liquid to vaporvapor
 During condensation, water vapor cools andDuring condensation, water vapor cools and
returns toreturns to liquidliquid statestate
 Water that falls to oceans and land isWater that falls to oceans and land is
precipitationprecipitation

16.  Groundwater isGroundwater is
precipitation thatprecipitation that
seeps into the groundseeps into the ground
and slowly flows backand slowly flows back
into soil, streams,into soil, streams,
rivers, and oceansrivers, and oceans
 Plants release a largePlants release a large
amount of wateramount of water
vaporvapor transpirationtranspiration

17. Let’s Review!Let’s Review!
What is the precipitation that is storedWhat is the precipitation that is stored
between or within rocks?between or within rocks?
Ground waterGround water
What is the burning of a substance called?What is the burning of a substance called?
(Think of the carbon cycle picture with the(Think of the carbon cycle picture with the
factories…)factories…)
CombustionCombustion

18. What is the gradual development of aWhat is the gradual development of a
community over time called?community over time called?
SuccessionSuccession
What process is the basis of the carbonWhat process is the basis of the carbon
cycle?cycle?
PhotosynthesisPhotosynthesis