Objectives:

1
Objectives

• To define and understand
• Population biology
• Characteristics of populationspopulations grow
• To estimate how popns grow
• initially w/ unlimited resources (exponential
  growth)
• then as resources become limited (logistic
  growth)
• What limits growth?
• What are patterns in survivorship?
• Trade-offs between growth, reproduction and
  parental care
• Human population growth

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• Definition of Popns
• What are characteristics of the popn?

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How is growth rate determined?

• Measuring popn size (N). Census/count
  individuals
• ? N (? B - D) (? I - E) survival and
  reproduction are key factors that determine
  change in N
• Growth of popn change in of individuals over
  time G
• Must calculate birth and death rates (b d)
• Find the rate of increase r
• Use r to estimate popn growth (G) for one time
  period r N

4

5

• The biotic potential of popn
• Depends on

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Age structure
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• Exponential growth implies unlimited resources
• But, limits on popn growth exist
• Carrying capacity ( K)
• Environmental resistance
• Logistic growth G r N (K-N)/K
• What happens when N gt K, N K, N lt K?

8

• Density-dependent and density independent
  limiting factors

Popn may temporarily increase above carrying
capacity Overshoot usually followed by a dramatic
crash
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Trade-off between births and density - as
density increases births decrease
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• Size of popns may fluctuate with regularity.
• Usually caused by multiple factors
• Snowshoe hare-lynx example

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Three types of survivorship curves

• Type I
• Type III -
• Type II

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Trade-offs between 1) frequency of reproduction,
2) of offspring, and 3) parental care.

• Big-bang reproduction
• Repeated reproduction

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• Human popn growing exponentially
• Humans alter rate of increase how?
• Humans alter environmental resistance how?

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• Largest countries China, India, U.S.
• Worldwide gt6 b. today (r 0.013)
• In 2050 10 b?
• Rapid growth in U.S. (1.8 annually)
• b and I
• U.S. 300 m (265 m 2003) now?
• 2050, 392 m