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Chapter 10

Chapter 10 Online Textbook BIO120 2013.docx

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Department
Biology
Course
BIO120H1
Professor
James Thomson
Semester
Fall

Description
Chapter 10 10/25/2013 2:52:00 PM CHAPTER CONCEPTS • Fluctuation is the rule for natural populations • Temporal variation affects the age structure of populations • Population cycles result from time delays in the response of populations to their own densities • Metapopulations are discrete subpopulations linked by movements of individuals • Chance events may cause small populations to go extinct 10.1 Fluctuation is the rule for natural populations  variation in density depends on 2 factors: o the amount the environment fluctuates o the stability of the population o if these are unstable, population will fluctuate  organisms react to habitats differently  some similarly o ex. Cycles of grouse in Finland Periodic cycle  A pattern of fluctuation with regular intervals between high and low values. 10.2 Temporal variation affects the age structure of populations  different classes of age structure also effect population growth 10.3 Population cycles result from time delays in the response of populations to their own densities  populations have an intrinsic periodicity Time delay  A delay in the response of a population or other system to change in the environment In a discrete-time model, the change in population size from one time interval to the next is Δ N( t) = N( t+ 1) − N( t) shows intrinsic growth rate can cause periodic cycles FIGURE 12.9A population may adopt one of three oscillation patterns. Damped oscillation  A pattern of oscillations with progressively smaller amplitude, as in the sizes of some populations approaching their equilibrium value. Compare with Chaos, Limit cycle (green line on graph)  Occurs when R exceeds 1 but is less than 2 Chaos  A complex, unpredictable pattern of oscillation, as in the sizes of populations with very high intrinsic rates of growth (red line on graph)  Occurs when R exceeds 2 illustrates time delays length of time delay  symbol τ FIGURE 12.10Time delays and density dependence create oscillations in population size.  development time + storage of nutrients can put off death rate to a later time, creating time delays 10.4 Metapopulations are discrete subpopulations linked by movements of individuals Habitat patch  An area of habitat with the resources and conditions necessary for a population to persist.  Individuals of a species living in a habitat create a “subpopulation” Metapopulation  A population that is divided into discrete subpopulations between which individuals move infrequently  2 things contribute to metapopulation dynamics: o growth within patches o colonization of empty patches  smaller the subpopulation, the higher chance of extinction  if consistent high migration between subpopulations, then all patches act as one large population  if never migrate, all subpopulations behave independently  intermediate amount of migration will occupy patches that have gone extinct, and shift from patch to patch rate of colonization within metapopulation c is single rate constant  metapopulation reaches equilibrium when rate of extinction and colonization are the same the proportion of occupied patches at equilibrium Rescue effect  Prevention of the extinction of a declining subpopulation by immigration of individuals from another, more productive subpopulation 10.5 Chance events may cause small populations to go extinct  smaller subpopulations more likely to die out than large subpopulations  3 randomness that affect populations: o Catastrophe o Environm
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