Population of Ecology

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Population of Ecology
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Ecology

• Study of the interactions of organisms in their
  biotic and abiotic environments
• Organism ? population? community ? Ecosystem
  ? biophsere

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Demographics of populations

• Demography statistical study of a population
  (density, distribution, growth rate)
• Population density - of individuals per unit
  area (can be misleading)
• Population distribution pattern of dispersal
  across an area (controlled by resources and
  limiting factors) clumped, random, uniform

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Population growth

• Rate of natural growth (r) based on birth and
  death rate.
• Biotic potential highest possible growth rate
  with unlimited resources.

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Survivorship curves

• Probability that newborn will survive to certain
  ages.
• Curve I characteristic of a population in which
  most individuals survive well past midpoint of
  lifespan. Ex. Large mammals, humans

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• Curve II survivorship decreases at a constant
  rate throughout the life span. Ex. Songbird,
  small mammals (death is usually unrelated to age)
• Curve III most individuals die young. Ex.
  Insects, fish, humans in less developing
  countries.

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Survivorship Curves
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Age distribution

• Age structure diagrams
• Increasing population
• Prereproductive ages is largest, birth rate is
  higher than death rate.
• Stable population (bell shape)
• Reproductive ages equal prereproductive ages
• Decreasing population (urn shape)
• reproductive ages is larger than prereproductive
  ages, postreproductive age is largest

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U.S. Population
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Population Growth Models

• 2 patterns of population growth
• Discrete breeding single reproductive event
• Continuous breeding many reproductive events
• Research not always have to be one or the other.

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Exponential Growth

• Number of individuals added each generation
  increases as the total of females increases.
• Lag phase growth is slow to start
• Exponential growth phase accelerated growth
• J shaped curve

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Logistic growth

• S-shaped curve
• Lag phase, exponential growth phase
• Deceleration phase growth slows
• Stable equilibrium phase little to no growth,
  BR DR

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Logistic Growth
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Carrying capacity

• Maximum of individuals of a species an
  environment can support.
• Exponential growth can not continue due to
  carrying capacity
• Resources become scarce
• Competition and predation
• Exponential growth occurs when population size is
  much lower than carrying capacity.
• Population stabilizes when carrying capacity is
  reached.

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Regulation of population size

• Density independent factors those that are not
  dependent on numbers
• Weather, natural disasters
• Density dependent factors occur because of
  population of species
• Competition, predation, parasitism
• Intrinsic factors? anatomy, behavior have an
  affect on population?

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Life History Patterns - Opportunistic

• r strategists
• Small individuals, short life span, fast to
  mature, many offspring, little/no care for
  offspring, early reproductive age
• Bacteria, fungi, insects, rodents, annuals

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Life History Pattern - Equilibrium

• K-strategists
• Large individuals, long life span, slow to
  mature, few and large offspring, care for
  offspring, most live to reproductive age
• Large mammals, birds of prey, long-lived plants

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Human population growth

• MDCs North America, Europe, Japan, Australia,
  growth is slow
• LDCs Latin America, Africa, Asia, population
  rising rapidly
• Ways to reduce projected population increase
• Strengthen family planning
• Education, raising status of women, reduce child
  mortality
• Delay onset of childbearing, wider spacing of
  births

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Population Growth and Environmental Impact

• LCD population growth in numbers
• MCD consume larger proportion of Earths
  resources
• Average family in North America consumes the
  amount of resources and produces wastes of 30
  people from India.