Bellringer • List 3 reasons why a population might decrease in size Population • Limiting Factor: A factor that causes population growth to decrease • 2 Types: o 1. Density-dependent: Factors that depend on the size of the population • Only become limiting when the population density becomes very high • Effects are intensified as the pop. Density increases o 2. Density-independent: Factors that do not depend, or are independent, of the size of the population • Are limiting regardless of the size of the population • Affect all populations in similar ways Limiting Factors Deforestation • Density-Independent • Human activities o Deforestation; over-hunting/fishing o Effects are harmful on population regardless of size Predation • Density-Dependent • Predation o The effect of predation intensifies as the population density of predators increases. Disease • Density-Dependent • Disease o High population densities make the spread of disease easier to transmit Natural Disasters • Density-Independent • Natural Disasters o Hurricane, tornado, flood, severe drought o Equally devastating to populations regardless of size Competition • Competition: o More members of a population = Less Available resources = More competition o Less members of a population = More available resources = Less competition Parasitism • Density-Dependent • Parasitism o High densities make it easier for parasites to find hosts, and spread diseases Severe frost • Density-Independent • Weather o Extremely hot/cold temperatures; frost o Adversely effects all populations regardless of their size. Creative Writing 1. Each group will work together to develop the beginning of a story. o Introduce your characters, setting, problem (limiting factor), and size of population in that characters community o Pass your story to the next group 2. Each group will read the introduction of the their new story, and: o Explain how the characters are being affected by the problem introduced in Part 1 (what fears/concerns does this organism have for his/herself and his population o Pass your story to the next group 3. Each group will read their new story, and write its ending: o Explain what happened to the character and his/her population as a result of the problem; will they be doing anything to re-build their population? o Explain the impact this problem had on the overall population size?