8[2].2 the processes of colonisation & succession

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  • 1. CHAPTER 8

2. 8.2 : THE PROCESSES OFCOLONISATION & SUCCESSION INAN ECOSYSTEM 3. Ecosystem, Community & Population Ecosystem : natural system formed by theinteraction of plants & animals between oneanother & also with their environment. Interaction between biotic & abioticcomponents balanced ecosystem balanced environment 1 of components is disturbed wholeecosystem upset not in balance Ecosystem = niche + habitat + population+ community 4. Niche : the status / role of an organism in itsenvironment Each species has its own niche in an ecosystem The types of food it consumes & the activity it carries out Examples : aphids, grass, ringed plover (kedidi gelang) - picked food from the surface of the shore, curlew probe deep into the mud (long, curve beak) Habitat : the natural place in which anorganism lives A Population : a group of organisms fromthe same species living in certain area A community : the plants & animals thatlive in a certain habitat 5. Process of Colonisation & Succession The process of colonisation : plantsstart to inhabit an uninhabited place &form a colony in the place Pioneer species 1st plant species toinhabit a new place Has special adaptive characteristics to adapt to the new environment Change the new habitat gradually to make the habitat more suitable for another species New habitat not suitable for the pioneer species replaced by another species succession begins 6. The process of succession : a certaindominant plant species in a habitat isgradually replaced by another plantspecies (successor species) Proceed stage by stage until a stable &matured community climaxcommunity (Eg. : tropical rain forest inMsia) 7. Process of Colonisation & Succession in a Pond In an unused mining pond The plants involved : Submerged water plants (pioneer) Floating water plants Amphibious plants Land plants Colonisation by pioneer species Unused & abandoned mining pond is not fertile & not suitable for any organism to live Pioneer species : phytoplankton (microscopic algae), submerged water plants (Hydrilla sp., Elodea sp., Utricularia sp., Cabomba sp.) 8. These pioneer organisms carry out photosynthesisto provide food for other organisms Pioneer die & decompose organic substanceproduced will be deposited at the bottom of thepond The banks of the pond are eroded & the soil settlesthe bottom of the pond more shallow, notsuitable for the submerged water plants,phytoplankton. Succession by floating water plants the successor replace the pioneer species 1stsuccession occurs Duckweed (Lemna sp. kiambang), water lettuce(Pistia sp.), water hyacinth (Eichornia sp. keladibunting) & lotus (Nelembium sp.) grow rapidly cover the surface prevent sunlight frompenetrating into the pond 9. The pioneer species cannot carry outphotosynthesis die The decayed organic substance from the pioneerspecies continued to be deposited pondsbecomes too shallow for the floating water plants Succession by amphibious plants 1st successor are replace by amphibious plants(2nd successor) that live in marshes (paya) Initially grow at the side of the ponds spread tothe centre of the pond The plants died more decayed organic substanceis deposited at the bottom of the pond The pond become more shallow & dried up suitable for other land plants 10. Succession by land plants 2nd successors are replaced by land plants shrubs & woody plants The process of succession continues to occur untila climax community is formed (tropical rain forest) take long time to complete 11. Colonisation & Succession ina Mangrove Swamp Mangrove swamp can be found at rivermouth that are sheltered from strong wave The mangrove swamp environmentalcondition (unsuitable for habitation) : Soft muddy soil Waterlogged soil which lacks of O2 Seawater with high salinity (high salt content) Strong sunlight & extreme heat 12. 3 types of mangrove trees are involved inthe process of colonisation & succession : Avicennia sp. & Sonneratia sp. (pioneer) Rhizophora sp. (successor) Bruguiera sp. (successor) Mangrove trees adaptive characteristicsto overcome the problems it faces in theenvironment : A root system that spread out widely provide support in soft muddy soil Pneumatophores breathing roots, protrude out of the soil enables gaseous exchange (waterlogged soil lack of O2) 13. The roots of mangrove trees can withstand thehighly saline seawater by having the higherosmotic pressure of the cell sap than thesurrounding water osmosis occurs [hydathodein the epidermis of leaves secrete excess saltsfrom the plants to control the osmotic pressure] Leaves : have thick cuticle & sunken stomata toreduce transpiration, thick & succulent to storewater Have viviparity seeds begin to germinate whilestill attached to the parent tree. the seeds willget sufficient O2 from the atmosphere duringgermination & will not suffocated for lack of air in awaterlogged environment. Also preventdehydration of seed 14. Avicennia sp. & Sonneratia sp.Zone The adaptations of pioneer : A root system that spread out widely Have asparagus-shaped pneumatophores very spongy & take air for respiration of the root system The widely spread roots trap mud accumulate the bank slowly raised, lesswater More suitable for Rhizophora sp. As thesuccessor 15. Rhizophora sp. Zone Higher & less waterlogged The adaptations : Has prop roots to support & anchor the tree in the soft muddy soil Has viviparity seeds to ensure the seedlings can grow, not carries away by the seawater The prop roots are able to trap mud. The pioneerspecies & the Rhizophora sp. die & decay,adding humus to the soil The banks are raised up even higher moresolid/ compact, fertile & less saline Not suitable for Rhizophora sp. replaced bythe Bruguiera sp. 16. Bruguiera sp. Zone Grow well in hard clay soil Have buttress roots for support & knee-shapedpneumatophores for gaseous exchange More sedimentation of decayed substances new bank are being build up seawards, oldbanks move further inland, away from the sea soil becomes harder, dry land is formed Bruguiera sp. are replaced by other types ofplants (coconut trees, Pandanus sp.) climaxcommunity (a few hundred years)