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FINAL EXAM - FINALEXAM 18:37 Chapter39 Ecology Ecology...

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FINAL EXAM 18:37 Chapter 39 Population Growth and Regulation Ecology Ecology The study of the interrelationships among living things and their nonliving environment Population Members of a particular species within an ecosystem Actually or potentially interacting How Does Population Size Change? Biotic potential Maximal growth rate given ideal conditions Produces exponential growth if not restrained Environmental resistance Factors that limit population growth e.g., food availability, space, access to mates, environmental factors Population growth = Biotic potential – Environmental resistance
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Exponential Growth Population change = (births – deaths) + (immigrants – emigrants) If we ignore migration Growth rate (r) = birth rate (b) – death rate (d) Exponential Growth To determine the number of individuals added to a population in a given time period, the  growth rate (r) is multiplied by the current population size Population growth = rN Time          Current N          Population Growth T = 0         N^0                   n/a T=1           n^1                   n^0+rN^0 T=2           n^2                   n^1+rN^1 Exponential Growth Curves Characterized by “J-shaped curve” Effect of Death Rates on Population Growth Death rate<Birth rate   Exponential Growth Just takes longer Death rate = or > Birth rate   No exponential growth Equilibrium or decline
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Which factor would not influence the size a population reaches over time? Distance traveled by migrants How is Population Growth Regulated? Populations Can’t Grow Exponentially Forever Finite amount of resources available Once they are limiting, population growth stops Can reach equilibrium or population may crash Lemming Population Cycles Conditions good: Boom, Conditions bad: Bust Environmental Resistance Limits Population Growth Decreases birth rate, increases death rate Density—dependent factors Predation Parasitism Competition (inter- and intraspecific) Density—independent factors
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Weather, natural disasters, pesticides, pollutants Causes populations to stabilize at or below carrying capacity Maximum population size an area can support long term A population growing exponentially ___. Has a J-shaped growth curve Has a per capita growth rate greater than zero A J-shaped growth curve is converted into an S-shaped one ___. When carrying capacity is reached The S-Curve of Population Growth Figure 39-5 The Effects of Exceeding Carrying Capacity Figure 39-6 Predators Help Control Prey Populations Density-dependent control More prey, easier for predators to find them Works both ways
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