Notes 2.6: Population Growth385-388

Models of Growth•Growth rates of a population can be determined by looking at birth and death rates

•Growth Rate = ______births – deaths_______# of individuals in the population

Growth Rate Practice•There were 37 births and 20 deaths in a seal population of 300 last month

•Growth rate = 37-20 = 0.057 last month

300

• Population is increasing in size

Growth Rate Practice•25 births per 200 sea otters in one week

•75 deaths per 200 sea otters in one week

•Growth rate = 25-75 = -.25 per week200

• Population is decreasing in size

Regulating Population Growth•Limiting factors: restrains population growth•Density-independent factors: no regard for population density• Examples: Weather, seasons, natural disasters

Regulating Population Growth•Density-dependent factors: increase or become more prominent when the population density increases•Ex. Predation, pollution, food storage, crowding

Exponential Growth (J-shaped curve)•Type of growth that shows slow growth at first, followed by increasingly faster rates of growth

•Birth and death rates are constant, births are higher than deaths

•Limited by density-independent factors

Exponential Growth•Ex. Bacterial growth

Logistic Growth (S-shaped)•Population growth starts out fast as there are more births than deaths

•Slows down, then levels off when the carrying capacity (K) is reached• (K): the maximum number of individuals the environment can

support over time

•Limited by density dependent factors

Logistic Growth•Most organisms follow this type of growth

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