Population Dynamics and Conservation

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Population Dynamics and Conservation
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Bringing Back the Sea Otter

• Keystone species
• Sea otter
• Sea urchin
• Kelp beds

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Ode to the Sea Otters

• Before
• 1 million sea otters lived in the pacific
• Hunters believed to have killed all the sea
  otters in the early 1900s

• After
• 1938 300 sea otters were counted
• After the U.S. Endangered species act and the
  marine mammal protection act, now about 2,300 sea
  otters swim the pacific

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Population Dynamics Depend On

• Size number of individuals in a population at a
  given time
• Density number of individuals of a population in
  a certain location at a given time
• Population dispersion
• Age distribution

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Population DispersionClumping

• Members in clusters or groups
• Food resources found in clumps
• Source of protection
• Helpful during mating season

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Uniform Dispersion

• Individuals of the same species compete for
  resources that are scarce and spread evenly.
• Cresote bush release toxins that prevent seeds
  from growing near it.

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Random Dispersion

• Unpredictable pattern
• Resources and conditions are uniform in the
  habitat
• Rare in nature

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Age Structure

• Prereproductive younger than sexual maturity
• Reproductive
• Postreproductive older than the maximum age of
  reproduction

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Biotic Potential Capacity for Growth

• Intrinsic rate of increase (r)
• Produce many offspring
• Exponential Growth

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Reaching the Carrying Capacity (K)

• Lack of food/ space in the petri dish?
• S-shaped curve (logistic growth)
• Amount of light, water, space, nutrients

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Which strategy would you use?

• Many offspring at young age
• Most offspring die before reproducing
• Generalist specie
• R-selected Species

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And what about these organisms?

• Few offspring
• Take care of youth
• Offspring usually lives to reproduce
• Specialist
• K-selected Species

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What limits growth?

• 4 Variables
• Births
• Deaths
• Immigration
• Emigration

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ZERO POPULATION GROWTH

• This occurs when
• (Births Immigration) - (Deaths Emigration)
  0

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MVP

• Q When do you stop using the same resource (ie.
  fish) for food?
• A You stop before reaching the resources
  minimum viable population (MVP) It is the min.
  pop. size needed for breeding

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Environmental Resistance

• All factors working together to limit the growth
  of a population
• Biotic Potential Envir. Resistance determine a
  populations Carrying Capacity

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Density Independent vs. Density Dependent
Population Control

• Density Independent
• Floods
• Hurricanes
• Earthquakes
• Landslides

• Density Dependent
• Competition
• Parasitism
• Predation
• Disease

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How have humans modified ecosystems?

• 1. Fragmentation and degradation
• 2. Simplifying ecosystem
• 3. Strengthening some populations of pest
  species and bacteria (speeding up nat. selection)
• 4. Eliminating some predators
• 5. Deliberately or accidentally introducing new
  species

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• 6. Overharvesting potential renewable resources
• 7. Interfering with normal chemical cycling and
  energy flow (CFCs, Ozone, etc.)

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What do we do about it???
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GLOBAL CPR

• C Conservation
• P Preservation
• R Restoration
• (We are the worldwe are the children)