Chapters 39-41

Chapters 39-41 - Chapter 39 Population Growth and...

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Chapter 39 Population Growth and Regulation 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 reacting How does population size change? Biotic potential o Maximal growth rate given ideal conditions o Produces exponential growth if not restrained Environmental resistance o Factors that limit population growth o E.g. food availability, space, access to mates, environmental factors Population growth= biotic potential – environmental resistance Exponential growth Population change=(births – deaths) + (immigrants – emigrants) If we ignore migration: Growth rate (r)= birth rate (b) – death rate (d) To determine the number of individuals added to a population in a given time period, the growth rate is multiplied by the current population size (rN) Characterized by a “J-shaped curve” Effect on death rates on population growth (figure 39-2) As long as the death rate is less that the birth rate, the population grows (it just takes longer) If the death rate equals the birth rate, equilibrium Regulation of population growth Populations cannot grow exponentially forever Finite amount of resources available Once they are limiting, population growth stops (can reach equilibrium or population can crash) Lemming Population Cycles (figure 39-4) Environmental Resistance limits population growth Decreases birth rate, increases death rate Density-dependant factors o Predation o Parasitism o Competition (inter- and intraspecific) Density-independent factors o Weather, natural disaster, pesticides, pollutants Causes populations to stabilize at or below carrying capacity o Maximum population size an area can support long term The S-Curve of Population Growth (figure 39-5) Effects of exceeding carrying capacity (figure 39-6) Predators help control prey populations Density-dependent control o More prey, easier for predators to find them Works both ways o Well fed predators make more offspring
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Population cycles in predators and prey (figures E39-1 and E39-2) Prey populations may grow unchecked in the absence of predators, competitors Survivorship curves (figure 39-9) Human Population Growth (figure 39-10) Human population Growing exponentially o Exponential growth will continue (age structure) o We continue to overcome environmental resistance Medical advances, Agricultural advances o Developed countries with more stable populations
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This note was uploaded on 11/08/2009 for the course BIOL 1001 taught by Professor Minor during the Spring '08 term at LSU.

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Chapters 39-41 - Chapter 39 Population Growth and...

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