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Thursday, August 27th Limiting Factors Restrict Growth Learning Goals • Factors that slow a population’s growth or prevent it from existing in certain areas • Outline the characteristics of populations that help predict population growth • Assess logistic growth, carrying capacity, limiting factors, and other fundamental concepts in population ecology Agenda • Population Notes • Lesson of the Kaibab WS Homework • Ch. 3 Quiz Monday Limiting Factors Restrict Growth • Density-independent factors: factors that affect a population regardless of its density − EX: Events such unusual weather, natural disasters, seasonal cycles, certain human activities—such as damming rivers and clear-cutting forests • Density-dependent factors: factors that affect a population related to its density − EX: Increased risk of predation, competition for mates, disease, stress, food availability − Operate only when the population density reaches a certain level. These factors operate most strongly when a population is large and dense. They do not affect small, scattered populations as greatly Carrying Capacity • The maximum population size of a species that its environment can sustain − An S-shaped logistic growth curve − Limiting factors slow and stop exponential growth 1 Carrying Capacity • When a population grows larger than carrying capacity, there aren’t enough resources and deaths outnumber births, population size brought back to carrying capacity • When a population shrinks smaller than carrying capacity, there are more resources and births outnumber deaths, bringing the population size back to carrying capacity Activity: Lesson of the Kaibab WS 2