Population Ecology

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Population Ecology
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Ecology

• ecology
• environment
• components
• biotic
• abiotic

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Ecology

• Hierarchy of Ecology
• biosphere
• ecosystem
• community
• population
• individual

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Population Ecology

• 2 characteristics of a population
• density
• dispersion

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Density

• we measure density by sampling
• mark and recapture method
• line intercept method
• point count method

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Population Distribution

• distribution patterns
• clumped
• uniform
• random

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Age Distribution

• distribution of males and females in each age
  group of a population
• used to predict future population growth

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Survivorship

• mirrors mortality
• expressed in survivorship curves
• plots surviving individuals at different age
  groups

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Survivorship

• three types of survivorship curves
• late loss (Type I)
• constant loss (Type II)
• early loss (Type III)

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Changes in a Population

• 3 factors determine population changes
• births
• deaths
• migration
• immigration
• emigration

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Population Dynamics

• J curve
• exponential growth
• measures optimal population growth
• rmax intrinsic rate of increase

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Population Growth

• example
• 10,000 birds in a population
• 1500 births and 500 deaths per year
• 1500/10,000 - 500/10,000 .10 or 10
• expressed by saying there is a 10 increase per
  bird per year

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Population Dynamics

• size of a population is limited to
• intrinsic rate of increase
• environmental resistance
• includes limitations the environment imposes on
  birth rate and death rate in a population
• food
• space
• predation
• parasitism

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Population Growth and Regulation

• carrying capacity (K)
• determined by
• renewable resources like water, nutrients, and
  light
• nonrenewable resources such as space

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Carrying Capacity

• logistic population growth
• r decreases as N increases
• K-N tells us of individuals population can
  accommodate
• S curve

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Population Growth Models

• K selected
• equilibrial populations
• live at density near limit imposed by resources
• r selected
• opportunistic populations
• live in environments where little competition is
  present

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Density Influence on Birth and Death Rates

• 2 mechanisms
• density independent
• density dependent

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Density Independent Factors

• unrelated to population size
• most important
• weather
• climate

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Density Dependent Factors

• increase effectiveness as population density
  increases
• especially affects long lived organisms
• include
• predation
• parasitism
• competition

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Human Population Growth

• J curve growth
• grows at a rate of about 80 million yearly
  (r1.3)
• Why doesnt environmental resistance take effect?

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Human Population Growth

• altering their environment
• technological advances
• the cultural revolution
• the agricultural revolution
• the industrial-medical revolution

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