Population Dynamics

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Chapter 6

• Population Dynamics

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Objective 1 2

• Appreciate the potential of exponential growth
• Draw a diagram of the J and S curves and explain
  what they mean

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What is Exponential Growth?
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Which Type of Growth is which?
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Which is Which?
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Geometric vs. Arithmetic Growth

• Geometric growth
• Population growth rate is expressed as a
  fraction the population is calculated by
  multiplying (J curve results)
• SLOW AT FIRST, THEN HUGE GAINS!!!!!!!!!!
• Arithmetic growth
• The population is growth at a constant amount per
  time. (linear curve results)
• STEADY RISE IN POPULATION

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Are both found here?
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What does this graph say?
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What is a J CURVE?

• Short gains early
• Big gains later
• Population is meeting/exceeding biotic potential
• Theoretical unchecked growth
• This is real for some populations (bacteria in
  particular..but not ALWAYS!)

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What is an S CURVE?

• The result of a population growth that has
  experienced environmental resistance.
• NOTE what happens to the influence of Env.
  Resistance as the population approaches the
  carrying capacity?

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What factors can we glean fromthe S (Sigmoidal)
curve?

• All populations have some limits.
• Reading a S curve can reveal those limits or at
  least give you an idea that are limits to look
  for.
• What limited our growth for so long????

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Objective 3

• Who was Thomas Malthus and what did he say about
  population growth?

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Thomas Malthus

• 18th century Economist link to article
• Elevated as man is above all other animals by
  intellectual faculties, it is not to be supposed
  that the physical laws to which he is subjected
  should be essentially different from those which
  are observed to prevail in other parts of
  animated nature. He may increase slower than most
  other animals, but food is equally necessary to
  his support and if this natural capacity of
  increase be greater than can be permanently
  supplied with food from a limited territory, his
  increase must be constantly retarded by the
  difficulty of procuring the means of
  subsistence.

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Population Oscillations
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So what did he say?

• Populations are cyclic
• They will flux with the environment
• Famine, disease, warall affect population

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Europe 0-2000
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And the US?
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Populations go thru one of two types of growth

• Irruptive or Malthusian Growth (unstable)
• Peaks, diebacks
• OR
• Logistic growth (stable)
• Constantly changing rate
• Be able to discuss
• the pros and cons of each.

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Objective 4

• Discuss environmental resistance and discuss how
  it can lead to logistic or stable growth

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Malthusian Strategies

• Low tropic levels, pioneer species, primary
  succession
• Move into disturbed environs, mature early, make
  many offspring, dont care for them, rely on
  sheer numbers
• Insects, rodents, parasites, annual plants
• Limited by predators, overshoot/diebacks, adapt
  quickly
• Extrinsic characteristics (pg. 129)

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Logistic Strategies

• Larger, live longer, mature more slowly, produce
  less offspring, have fewer predators, care for
  offspring longer
• Wolves, elephants, bears, primates
• intrinsic characteristics (pg. 129)

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Objective 5

• Define fecundity, fertility, birth rates, life
  expectancy, death rates, survivorship

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Fecundity

• The physical ability to reproduce

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Natality

• Producing of new individuals through hatching,
  birth, germination or cloning

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fertility

• A measure of the offspring produced

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Birth Rates

• Crude birth rates for many countries is
  declining..

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Life expectancy

• Life expectancy calculator
• Living to 100

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Death rates

• Causes of  Death Number of Deaths Rate per
  100,000 
• 15-24 years
• All causes 32,699 
• Accidents and adverse effects 13,872
• Motor vehicle accidents 10,624
• All other accidents and adverse effects 3,248 
• Homicide and legal intervention 6,548 
• Suicide 4,369
• Malignant neoplasms, including neoplasms of
  lymphatic and hematopoietic tissues1,642 
• Diseases of heart 920 
• Human immunodeficiency virus infection 420 
• Congenital anomalies 387 
• Chronic obstructive pulmonary diseases and allied
  conditions 230 
• Pneumonia and influenza 197 
• Cerebrovascular diseases 174 
• All other causes (Residual) 3,940
• More death rate statistics 
• Countries death rates

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survivorship

• The percentage of offspring born at the same time
  that survives to a certain age

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Objective 6

• Compare and contrast density dependent and
  density independent population processes

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Density-Independent Factors

• Abiotic components of the ecosystem

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Density-Independent Factors

• Natural disasters or extreme weather events can
  help or hurt a population

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What effect did this eruption have on the
habitat? The organisms?
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Weather Patterns with a Global Impact!
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Do these occurrences really REGULATE the
population?
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Density-Dependent Factors

• Reduce the population size
• Drop in natality or increase mortality
• HOW?
• Either
• Intraspecific interactions
• Interspecific interactions

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Predator-Prey cyclic relations
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Who do I prey on?
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What might cause this change?
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Stress and Crowding
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The Summary

• The summary is very good.
• A must read for all.
• You too, Mary.