Population Ecology

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PopulationEcology
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Population

• Number of Individuals of the Same Species that
  live together in one area or place

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What dynamics might be involved in predicting
population growth?

• Population Size
• Population Growth Rate
• Carrying Capacity
• Limiting Factors

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Population Size

• Number of individuals in a population
• Growth occurs when the birthrate is greater than
  the death rate.

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Population Growth Curves

• Exponential
• growth
• Population increases by a constant proportion per
  unit of time
• At this growth rate the population exhibits a
  J-shaped curve

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Population Growth Curves

• Logistic growth
• Population increases rapidly for a period of
  time, its growth begins to slow, and ultimately,
  growth stops.
• At this growth rate the population exhibits an
  S-shaped curve.
• K (carrying capacity) maximum population size
  that an environment can support

K
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Factors That Control Population Growth

• Populations dont grow indefinitely because of
  Limiting factors.

• Limiting Factors
• Competition
• Predation
• Parasitism
• Crowding
• Stress
• Disease

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Competition

• Primary sources of Competition
• Food
• Water
• Space
• Mates

• Situation in which two or more organisms attempt
  to use the same scarce resource (this could be a
  food source, a good location for capturing
  sunlight by plants, a particular nutrient, etc)

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Predation

• A relationship between two organisms in which one
  organism (predator) kills and devours another
  organism (prey).
• Affects population size of both predator and the
  prey. Often cyclical.

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Parasitism

• The relationship between two organisms where one
  organism benefits (parasite) and the other is
  harmed (host).

• Example Tapeworm
• You are harmed because it lives off your
  intestinal fluids
• Segments break off to form a new worm!

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Biodiversity

• The number of species living within an ecosystem.

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How Populations Evolve

• Hardy-Weinberg Principle
• The frequencies of alleles in a population do not
  change unless evolutionary forces act on the
  population.
• p2 2pq q2 1

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How Biodiversity Impacts Population Growth

• 6 forces that cause populations to evolve
• Mutation ultimate source of all variation
• Migration movement of organisms from one
  population to another, creates gene flow.
• Nonrandom mating when individuals prefer to
  mate with others of their own genotype,
  inbreeding is an example.
• Genetic drift random change in response to
  their environment.
• Natural selection Survival of the fittest.
• Extinction- species that have disappeared
  permanently.