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Population Ecology Chapter 52
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Population - group of individuals living in same area at same time. Population density - # of individuals per unit area. Population dispersion - arrangement of population in area.
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Dispersion patterns happen 3 ways. 1 Clumped dispersion - individuals in groups. 2 Uniform dispersion – individuals evenly spaced out. 3 Random dispersion - individuals live regardless of where other individuals live.
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CLUMPED
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UNIFORM
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RANDOM
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Demography - study of statistics of a population. Life tables - show summary of specific ages of population and survival rates.
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Survivorship curve - can see how many individuals are alive at specific ages.
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Reproductive tables - reproductive rates at various ages. Focus only on females and not males in these tables.
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Life history - traits that affect organism’s schedule of reproduction and survival. 1 Big-bang reproduction (produce large number of offspring sometimes followed by the organism’s death) Known as semelparity.
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The agave plant
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2 Repeated reproductive episode - organism produces smaller numbers of offspring. This is also known as iteroparity.
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Change in population - # of births minus # of deaths during that same time. Equation : N/ t = r; r= difference between birth and death rates, N= change in population size, and t= change in time.
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Limitations on population growth due to resources. K = carrying capacity. Carrying capacity – max # of individuals an area can handle based on resources.
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Logistic population growth model - incorporates affect of population density on rate of increase. Carrying capacity cannot be exceeded - graph is S-shaped.
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Carrying capacity equals change in population size
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Cannot exceed carrying capacity Carrying capacity
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Life histories - predict how population will reproduce. 1 K-selection - live and reproduce around K. 2 r-selection - high rates of reproduction, but live in environments where populations are well below K.
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2 factors determine the growth of a population. 1 Density-dependent factors increase their effect as density increases (negative feedback) 2 Density-independent factors - not affected by density increase.
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Negative feedback - caused by several different factors. One - resources (force populations to stop reproducing if conditions are crowded)
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As # of planted seeds increase, # reproducing decreases
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Competition for resources can force decreased reproduction rates. Need to defend space can reduce population size. Predation can decrease the size.
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Human population has been steadily growing since 1650. Zero transition growth # of births = # of deaths. Only way to steady out population growth.
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One of the difficulties with population growth is looking at the distribution of ages. The problem is that the carrying capacity of Earth has not been determined.
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http://www.youtube.com/watch?v=GECJc W2Ifm4http://www.youtube.com/watch?v=GECJc W2Ifm4
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