Population Dynamics

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Population Dynamics
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Populations

• A population is a group of organisms of the same
  species that live in a particular place at one
  time.
• A population could be a species of plants,
  animals, bacteria, or people, living in a given
  area (for example, bass living in an isolated
  pond).

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Population Dynamics

• Populations are constantly changing and we need
  to keep up with the changes. The study of human
  population is demography. Some measures are
• Birth Rate Number of births in a given time.
  (U.S. 4 million per year)
• Death Rate Number of deaths in a given time.
  (U.S. 2.4 million per year)
• Life Expectancy how long the avg. person lives.
  (U.S. men 77, women 80)

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Age Structure Diagrams

• Distribution of people of different ages (shown
  histogram)
• Also Shows Sex Ratio number of males to females.

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Other histograms
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Population Growth Rate

• Amount by which a pop. changes over a period of
  time, depends on 4 processes birth rate, death
  rate, immigration, and emigration.
• BR immigration - DR emigration growth
• Growth of a population is usually exponential,
  only contained by limiting factors (food, water,
  space,density)

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Exponential Growth J-shaped curve. Unlimited
growthex. Humans
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Logistic Growth S-shaped curve. Pops growth
slows because of a limiting factor (at carrying
capacity) ex. Rabbits in the wild
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Exponential and Logistical Growth Graph
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Density Factors

• Density-independent affect all populations in
  similar ways regardless of size. Fires,
  deforestation, dams, floods, hurricanes etc
• Density-dependent factors a limiting factor
  that depends on the size of a population. The
  more crowded more competition, predation,
  parasitism, and disease. CYCLIC