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

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

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

    • CHAPTER 8
    • 8.2 : THE PROCESSES OFCOLONISATION & SUCCESSION INAN ECOSYSTEM
    • Ecosystem, Community & Population• Ecosystem : natural system formed by the interaction of plants & animals between one another & also with their environment.• Interaction between biotic & abiotic components  balanced ecosystem  balanced environment• 1 of components is disturbed  whole ecosystem upset  not in balance• Ecosystem = niche + habitat + population + community
    • • Niche : the status / role of an organism in its environment • 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 an organism lives• A Population : a group of organisms from the same species living in certain area• A community : the plants & animals that live in a certain habitat
    • Process of Colonisation & Succession• The process of colonisation : plants start to inhabit an uninhabited place & form a colony in the place• Pioneer species – 1st plant species to inhabit 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
    • • The process of succession : a certain dominant plant species in a habitat is gradually replaced by another plant species (successor species)• Proceed stage by stage until a stable & matured community  climax community (Eg. : tropical rain forest in M’sia)
    • 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.)
    • • These pioneer organisms carry out photosynthesis to provide food for other organisms • Pioneer die & decompose  organic substance produced will be deposited at the bottom of the pond • The banks of the pond are eroded & the soil settles the bottom of the pond  more shallow, not suitable for the submerged water plants, phytoplankton.• Succession by floating water plants • the successor – replace the pioneer species  1st succession occurs • Duckweed (Lemna sp. – kiambang), water lettuce (Pistia sp.), water hyacinth (Eichornia sp. – keladi bunting) & lotus (Nelembium sp.) grow rapidly  cover the surface – prevent sunlight from penetrating into the pond
    • • The pioneer species cannot carry out photosynthesis  die • The decayed organic substance from the pioneer species continued to be deposited  ponds becomes 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 to the centre of the pond • The plants died  more decayed organic substance is deposited at the bottom of the pond • The pond become more shallow & dried up  suitable for other land plants
    • • Succession by land plants • 2nd successors are replaced by land plants – shrubs & woody plants • The process of succession continues to occur until a climax community is formed (tropical rain forest)  take long time to complete
    • Colonisation & Succession in a Mangrove Swamp• Mangrove swamp – can be found at river mouth that are sheltered from strong wave• The mangrove swamp environmental condition (unsuitable for habitation) : • Soft muddy soil • Waterlogged soil which lacks of O2 • Seawater with high salinity (high salt content) • Strong sunlight & extreme heat
    • • 3 types of mangrove trees are involved in the process of colonisation & succession : • Avicennia sp. & Sonneratia sp. (pioneer) • Rhizophora sp. (successor) • Bruguiera sp. (successor)• Mangrove trees adaptive characteristics to overcome the problems it faces in the environment : • 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)
    • • The roots of mangrove trees can withstand the highly saline seawater by having the higher osmotic pressure of the cell sap than the surrounding water  osmosis occurs [hydathode in the epidermis of leaves secrete excess salts from the plants – to control the osmotic pressure]• Leaves : have thick cuticle & sunken stomata to reduce transpiration, thick & succulent to store water• Have viviparity seeds  begin to germinate while still attached to the parent tree. the seeds will get sufficient O2 from the atmosphere during germination & will not suffocated for lack of air in a waterlogged environment. Also prevent dehydration of seed
    • 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, less water• More suitable for Rhizophora sp. As the successor
    • 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 pioneer species & the Rhizophora sp. die & decay, adding humus to the soil• The banks are raised up even higher  more solid/ compact, fertile & less saline• Not suitable for Rhizophora sp.  replaced by the Bruguiera sp.
    • Bruguiera sp. Zone• Grow well in hard clay soil• Have buttress roots for support & knee-shaped pneumatophores – for gaseous exchange• More sedimentation of decayed substances  new bank are being build up seawards, old banks move further inland, away from the sea  soil becomes harder, dry land is formed• Bruguiera sp. are replaced by other types of plants (coconut trees, Pandanus sp.)  climax community (a few hundred years)