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Aim: How do ecosystems change over time? Ecological Succession1 • The process by which an ecosystem changes over time – often from a barren piece of land to a complex ecological community (depending on climate) Ecological Succession In a Forest • As time passes grasses grow & then get replaced by shrubs and eventually a forest will form. • Why do the grasses disappear? –The large shrubs and trees prevent light from reaching the grasses. Ecological Succession in Ponds & Lakes: As time progresses, the pond gets filled in with dead organic matter. The dead organic matter takes the place of the water in the pond or lake. Eventually (through succession) a forest may form where the pond once was. What is the final state of ecological succession • A climax community with great biodiversity Plant adaptation / succession 1:48 Destruction of Climax Communities • Fires, volcanic eruptions, tsunamis, deforestation, acid rain. • Their destruction often (but not always) means the birth of a NEW community via succession. Are forest fires an ecosystems worst nightmare? Why or why not? Fire in the Forest 2:25 Soil Formation: • Lichens (fungus and green algae) & weather break down rock into its minerals. • Dead Organic materials are added to the minerals Maintaining Soil: • The plant roots hold on to the soil & prevent erosion (washing away of valuable material). • How could erosion cause a problem for an ecosystem?