Population Ecology

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http//www.ibiblio.org/lunarbin/worldpop
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World Human Population
http//www.census.gov/ipc/www/worldpop.html
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U.S. Human Population
http//eire.census.gov/popest/archives/pre1980/pop
clockest.txt
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World Human Population
http//www.census.gov/ipc/www/worldpop.html
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Population Characteristics

• Population ecology is the study of interactions
  within populations (i.e., intraspecific
  interactions)
• Recall that populations are groups of interacting
  conspecifics (e.g., inter-mating)
• We can characterize individual populations in
  terms of there
• Size (average vs. variation)
• Density ( impacts on size density dependence)
• Patterns of Dispersion
• Demographics (age structure, sex ratios)
• Rates of growth (or decline)
• Limits on population growth

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Population Dispersion
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Why Different Types?
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Population Demographics
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Age-Structure Pyramids
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(Cohort) Survivorship Curves
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More-Complicated Curve
II or III
I or II
I (senescence)
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Babies!
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Reproduction

• Age of first reproduction (sexual maturity)
• Clutch size
• Investment in individual progeny
• Tradeoff between reproduction and survival
• Number of reproductive episodes per lifetime
• Upside of Semelparity
• Upside of Iteroparity

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Semelparity
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Iteroparity
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Growth Without Limits
r 1.0
r 0.5
r population growth rate
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Impact of Limits
Imposition of limits
dN/dt r ? N ? (K-N)/K
New or Changing Environment (no competition /
limits)
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Environmental Resistance
K
N
N/K Environmental Resistance
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Maximizing Yield
dN/dt is maximized when Nr is maximized
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Fitting Curves to Real Pops.

• Logistic growth model does not consider the
  effects of predators or interspecific
  competition, so fails to predict the complexities
  of the density of many natural populations as a
  function of time
• Nevertheless, it serves as good null hypothesis

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Oscillations about K
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r versus K Selection
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Boom and then Bust
r-like
Water flee (Daphnia magna) is adapted to exploit
new environment high growth rate, resistant eggs
produced before crash.
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Boom and then really Bust
Reindeer introduced to Pribilov island. Initial
exponential growth, crash, complete extinction.
r-like
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Boom and sort of Bust
Predators were removed from Kaibab plateau. Mule
deer population size increased from 4,000 to
hundred thousand, then dropped and stabilzed at
10,000.
K-like?
r-like?
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Boom but not much Bust
Sheep introduced to Tasmania rapid initial
growth, overshoot, drop, fluctuation around
carrying capacity.
r K-like
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Boom Bust Boom Bust Boom Bust
Hare r tendencies kept under control by
1predation or by their food supply?
The familiar 10-11 year hare-lynx cycle might not
be true. Biased data. (http//www.behav.org/ecol/w
ildlife/w_06_populations.htm)
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Density-Dependent Limits (to max K)
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Density-Independent Factors (e.g., weather)
Good Times! (in Australia)
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Density-Dependent vs. Independent Limits
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Large Variation in Pop. Size
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QuestionWhy are humansdestroying the earth?
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QuestionWhy do locusts destroy crops?
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Limits Locust Freedom Without Responsibility
Ive got my rights!
Its a free country!
Whos going to stop me?
Destroyed Crops (destruction of environment)
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QuestionWhy do some microbes make us sick?
(hint it often has much to do with selfish greed
causing environment destruction)
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Limits Pathogen Freedom Without Responsibility
Its a free country
Whos going to stop me?
Ive got my rights!
Disease! (destruction of the body environment)
Bacterial pathogens
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Limits Paul Ehrlich and the Population Bomb
Impact Population Affluence Technology
Impact Population Affluence Efficiency
Consumption per Baby Resource Efficiency

(or afluence technology)
Consumption Damages Resources (a.k.a., the
environment)
There are only so many resources to use up!
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Human Population Growth
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Human Freedom Without Responsibility
Whos going to stop me?
Its a free country
Ive got my rights!
Destructamundo! (destruction of environment)
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Link to Next Presentation
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Acknowledgements
http//www.uta.edu/biology/marshall/2343/Biol2343_
lecture_16.ppt Pearson Education, Inc. publishing
as Benjamin Cummings
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Growth Without Limits