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How Populations Grow A. Population size: total # of organisms. B. Population growth: increase in size of population with time. C. Population density: # of individuals per unit area. D. Limiting factors: conditions that keep organisms from reaching their maximum population numbers. • what are some examples?? Examples of limiting factors: Competition Predation Parasitism Disease Climate Humans E. Population Growth Curve 1. J-Shaped curve: under ideal conditions; exponential growth # Time 2. S-Shaped curves: population gets to a stable point, limiting factors have influenced growth; Logistic growth # Time F. Carrying capacity: maximum population level that can be supported with the resources available. 1. Not only during that organism’s lifetime, but also future populations. 2. What is the earth’s carrying capacity? G. Density-independent limiting factors: something that affects all populations, regardless of size. 1. Ex: storms or hurricanes, climate H. Density-dependent factors: Effect increases with crowding and can bring a pop under control. 1. Ex.- Disease, predators, parasites I. Human population growth: -controlled by war, famine, and disease 1. Demography: study of human populations 2. Demographic transition: change from high birth and death rates to low birth and death rates. J. Competition 1. Intraspecific – between the same species 2. Interspecific – between different species