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2.3 Ecosystems are always changing Population size changes in response to – food supply – Predation – Seasons – birth rates A limiting factor, such as water, light, or food, can affect population survival and growth. The carrying capacity of an environment is the maximum population it can support. At carrying capacity a population stops growing. Ecosystems change over time. Succession is a gradual series of changes that take place in an ecosystem after a disturbance. There are two types of succession • Primary • Secondary Primary - starts from an environment that is mostly empty of life. • Examples - After the retreat of a glacier, for example, or on new rock produced by a volcano, life can begin to return Pioneer species - 1st species that moves into the barren environment and begin the task of creating soil. Examples: moss, lichen Secondary - occurs in areas that have soil with roots and seeds below the surface. • life already survives. • may begin after a fire or flood disturbs the ecosystem.