Populations by dffhrtcv3



               • number of individuals of a species in a
                 defined place and time.

10 Feb. 2009                   Populations.ppt             1
               5.3.1 Changes in populations

       • ΔN = +B +I –D –E
               +B = natality (the number of births)
               +I = immigrants (immigration rate)
               – D = deaths (death rate)
               – E = emigrants (emigration rate)
               (For many [most] natural populations I and E
                 are minimal.)

10 Feb. 2009                    Populations.ppt               2
5.3.2: S-Shaped Population Growth Curve
5.3.3-Explain the reasons for the
    exponential growth phase
• Plentiful resources (food, light, space, etc.)
• Little to no competition
• Abiotic conditions favorable (temp.,
  dissolved oxygen, soil, etc.)
• Little to no predation or disease

  NO! 5.3.3-Explain the reasons
    for the transitional phase
• Increasing competition between individuals
  in the population (which type of
  competition is this?)
• Predation increases (predators attracted to
  growing food source)
• Disease spreads more easily due to a higher
  density of individuals
5.3.4-Explain the reasons for the
         plateau phase
• Resources and/or space become limited
  (food supply, light, water)
• Build up of waste (excrement, carbon
• Predation
• Disease
          Carrying Capacity
- The plateau phase defines the carrying
 - Defined as the number of individuals that
   the habitat can support
- It is not a constant, it fluctuates with
   changing conditions (food availability,
   climate, time of the year, etc.)
     G.5.1 Distinguish between r and k strategies

Life History trait       r-adapted,             K-adapted,
                         Opportunistic          Equilibrium
Offspring                Many, small (high r)   Fewer, large (low r)
Offspring survival       Low                    High
Parental care            Rare                   Common
Reproductive age         Early                  Later
Reproduction             Once                   Many times
Habitat                  Unstable, temporary    Stable, permanent
Population regulation    Density independent    Density dependent
Population fluctuation   Fluctuates greatly     Stable near K
Survivorship Curve

Make a list of examples of organisms
    that employ each strategy
R-Strategists          K-Strategists
  G.5.2-Discuss environmental
  conditions that would favor r-
    strategies or k-strategies
• Large environmental changes favor r-
  strategists due to their immense number
• With so many offspring, a few are likely to
  survive even in changed conditions
• Ecological disruptions such as natural
  disasters or succession favor highly
  adaptable organisms  higher degree of
  variation (have many offspring)
      K-strategists favor stable
      environments due to…..
• their long gestation period
• High degree of parental care (example:
  nursing mothers require more food)
• Only a few offspring, if they all die the line
  will not continue
 G.5.3- Describe how to estimate
   population size with mark-
     capture-release method
• Mark all the individuals in the population that you
  find in one area
• Wait
• In the same area, catch as many as you can again
  and mark any individuals that are not already
• The proportion of marked to unmarked individuals
  in the second sample is the same as the proportion
  of the originally marked individuals to the whole
• Repeat the method at least five times
    Capture mark release Equation:

•   n1= number marked in first sample
•   n2=total number caught in second sample
•   n3= number marked in second sample
•   N= size of the whole population

    n3 = n1            N = n1 x n2
    n2   N                     n3
 G.5.4 Describe methods used to
 estimate the size of commercial
            fish stocks
• Gather information from fishers (number and
  kinds, questionnaires, logbooks)
• Use research vessels to:
   – Cast nets and sample many locations randomly
   – Echo sounders (sometimes even the species can be
     detected), trawling is used to verify
   – Age of the fish can be indicated by counting the rings
     on their ear bones
   – Tagging fish (similar to mark-capture-release method)
   – Using mathematical models
 G.5.5-The concept of maximum
 sustainable yield in fish stocks
• The highest proportion of fish that can be
  removed without jeopardizing this
  maximum yield in the future.
• If there are not enough adults, there will not
  be enough offspring
• Often females are protected over males for
  this reason (example: Dungeness crabs)
G.5.6 International measures that
would promote fish conservation
• All seafood species have declined by 29%
• If this continues, there will be no more
  commercial fishing by 2048
• Some stocks have already declined by much
  more than the above average (North sea cod
  by 75%, North Atlantic Haddock by 50% in
  one year!)
G.5.6 International measures that
would promote fish conservation
• Regulate trawling (lots of by-catch)
• Rebuild depleted populations (fish farms,
  protecting spawning grounds)
• Eliminate wasteful fishing practices (mostly nets)
• Enact and enforce catch limits
• Provide funds for research on populations
• Encourage scientist-fisher relationships
• Establish marine reserves (no fishing there!)

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