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Chapter 34 Regulation of Populations Factors affecting population size Define the following: Population: Birth rate: Death rate: Population dynamics: Population density: Carrying capacity: What is the relationship between birth rate and death rate when dynamic equilibrium is reached in a population? 1 Chapter 34 Although each species has enormous reproductive potential, populations do not increase in size indefinitely under natural conditions due to environmental resistance. Factors which affect the size of a population fall into 2 categories: Density-independent factors affect population growth regardless of population density. These factors tend to cause a sudden drastic reduction in population number, although after sufficient time the population normally makes a full recovery. These factors are usually extreme and will wipe out most of a population whether it is densely packed or sparsely distributed in the ecosystem. e.g. forest fire, lava flow, flood, drought, unusually extreme temperatures. In contrast, some factors affect a population only once it has reached a particular density. Up to that point, a small population will increase - until its growth rate is affected by a factor related to population density. Density-dependent factors affect populations once they have reached a certain size and density. Write brief notes on the following density-dependent factors : Competition for food: Toxic wastes: Parasitism and disease: Predation: 2 Chapter 34 Predator-prey interactions Study graphs at Figs 34.7 and 34.8 and make sure you understand what they show. Why is the regulation of population size seen as an example of homeostatic control? 3