Population

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Population
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Final Exam Times

• MWF 1030-1120 class
• Monday, December 7th, 1010-1150
• MWF, 1130-1220 class
• Wednesday, December 9th, 1010-1150

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How do populations grow?
Population
Deaths
Births
Immigration
Emigration
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Population Growth Models

• Linearprobably not realistic
• Exponential (geometric) dN/dt rN
• rintrinsic rate of increase(b-d)
• Npopulation size
• Logistic dN/dt rN (K-N/K)
• Includes carrying capacity term (K-N/K) or
  (1-(N/K))
• More realistic due to environmental factors
• Others with competition, stage-based (age or size
  specific), etc.

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Geometric or Exponential Growth
Phlox drummondii
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Anatomy of the Exponential Growth Model
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Another example of exponential growth whooping
cranes
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Logistic Growth (includes carrying capacity term)
Yeast
African Buffalo
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A word about your projects the MORE formula

• You need to be motivated. This means that you
  need to keep in touch with other people in your
  group and other important people like Jeff Aker
  and plant operations folk.
• You need to be organized. Make sure you know who
  is doing what and when and where (and why and
  how).
• You need to be responsible. Make sure you know
  what is expected and that you complete the
  expected work. No more hand-holding.
• Be an elephant

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What determines limits to Population Growth?

• Density-dependentbiotic factors like disease,
  competition, or predation
• Density-independentabiotic factors like climate,
  fire, nutrients, sunlight, etc.

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Galapagos Islands

• Darwin studied in 1830s
• Found some birds he thought were unrelated
• In fact, they were closely related finches in
  different species

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Adaptive Radiation Galapagos Finches
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To quote Darwin

• "It is very remarkable that a nearly perfect
  gradation of structure in this one group can be
  traced in the form of the beak, from one
  exceeding in dimensions that of the largest
  gros-beak, to another differing but little from
  that of a warbler."

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Environment Varies Leading to Density independent
regulation of population
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Medium Ground Finch benefits from increased
rainfall
El Nino Year
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El Nino Year
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Cactus Finches

• Eat flower pollen from buds
• Eat seeds
• Drink nectar
• Eat insects
• Some seed dispersal
• Some pollination

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Opuntia helleri prickly pear cactus

• El Nino damaged them by water-logging and salt
  spray (density independent factors)
• Damage is also by competition from other plants
  and cactus finches (density dependent factors)

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Cactus flower abundance and damage by cactus
finches
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Survivorship curves (from chapter 10)
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r vs. K-selection

• r-selected

• K-selected

• Small size
• Many offspring
• Cheap to produce
• Little investment in offspring
• Type III survivorship curve
• Early and one-time reproduction

• Large size
• Few offspring
• Expensive to produce
• Much investment in offspring
• Type I survivorship curve
• Later and repetitive reproduction

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r vs. K-selection
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Human Population Growth
LOOK!! Humans are subject to carrying capacity,
too!!

• Expected to reach 9.5 billion or so by 2050
• Most of this in developing countries

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Trends in human population growth

• 1800 1 billion
• 1930 2 billion
• 1960 3 billion
• 1975 4 billion
• 1987 5 billion
• 1999 6 billion
• Current 6.8 billion

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Human Population Growth

• 3 Revolutions
• Agricultural 10,000 ybp
• Industrial 225 ybp
• Medical/technological 50 ybp

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Age-Sex Pyramids developed vs. developing
nations
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The Demographic Transition
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The Impact of Epidemics
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With and without AIDS
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Do big diseases make a difference?
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U.S. Population
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What about those big bad diseases?
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Let natural selection remove the Joe Sixpacks