Ecosystems: Populations and Succession

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Chapter 4

• Ecosystems Populations and Succession

2
Population Dynamics Growth Curves
3
Population Dynamics Biotic Potential vs.
Environmental Resistance
4
Population Dynamics

• Carrying Capacity the maximum population size
  that an environment is capable of maintaining
  over the long-term
• Dynamic Equilibrium additions and losses from a
  population occur such that the population size
  fluctuates around a median value

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Mechanisms of Equilibrium Predators
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Mechanisms of Equilibrium Herbivory
Third Principle of Ecosystem Sustainability The
size of consumer populations is maintained such
that overuse does not occur
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Mechanisms of Equilibrium Competition
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Mechanisms of Equilibrium Balanced Herbivory
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Mechanisms of Equilibrium Introduced Species

• Introduced Species enter an ecosystem without
  predators and diseases and therefore can grow
  without check
• Many cause extensive changes to ecosystems
• Examples include zebra mussels, water hyacinth,
  kudzu, Asian longhorn beetle, and purple
  loosestrife

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Disturbance and Succession Primary Succession
Begins without any life present Bare rock,
fresh lava
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Disturbance and Succession Secondary Succession
Begins with some life present Old fields,
hurricane damage, logging
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Disturbance and Succession Aquatic Succession
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Disturbance and Succession Resilience

• Ecosystems are able to respond to disturbance by
  growing back
• Many are adapted to periodic disturbance fire in
  the prairie, flood in riparian areas, forest
  canopy gap- dynamics
• Fourth Principle of Ecosystem Sustainability Ecos
  ystems show resilience when subject to
  disturbance
• Fifth Principle of Ecosystem Sustainability
  Ecosystems depend on biodiversity

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Humans

• Adaptive Management
• Plan for long-term
• Conserve natural resources
• Minimize alien species
• Use land in accordance with its normal potential
• Examine local decisions for regional impact
• Retain large, connected habitat areas
• Monitor and reassess management approach
• Population Pressures
• What is our population doing now?
• When do we reach carrying capacity?
• What happens in the mean time?

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Summary

• Population Dynamics growth curves, dynamic
  equilibrium
• Mechanisms of Equilibrium predation, herbivory,
  competition, balanced herbivory, introduced
  species
• Disturbance and Succession Primary and
  Secondary Succession, Aquatic, Resilience,
  Biodiversity
• Humans adaptive management, population size