Population Dynamics

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Population Dynamics

• Ch. 35

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Measuring Populations

• Population density of individuals of a
  particular species per unit area

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Measuring Populations, cont.

• Sampling used to estimate size of population
• Quadrats count all organisms in a block and use
  this to estimate population size
• Indirect counting count nests, burrows, etc
  instead of organisms
• Mark recapture trap animals, mark them,
  release, recapture and count marked vs. unmarked

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Limiting population growth

• Limiting factor a condition that can limit
  population growth
• Ex space, food, disease
• Carrying capacity the number of organisms in a
  population that the environment can maintain
• Birth rate and death rate are about equal

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Limiting population growth

• Density-dependent factors a factor that limits
  population growth more as the population density
  increases
• Ex food, disease that spreads by contact
• Density-independent factors a factor that
  limits population and is unrelated to population
  density
• Ex extreme weather

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Types of population growth

• Exponential population multiplies by a constant
  factor at constant time intervals
• there are few factors that stop overall growth
• Also known as J-curve

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Types of population growth

• S-curve population begins growing
  exponentially, but environmental factors begin to
  limit growth population stops growing or may
  begin to decrease

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Types of population growth

• Boom and bust increase rapidly (boom) and then
  decrease rapidly (bust)

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Population interactions

• Interspecific competition two or more species
  rely on the same limited resource
• Competitive exclusion when one species succeeds
  over the other due to limited resources
• Niche each organisms unique living
  arrangement, such as habitat, food, time when
  active, etc

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Population interactions

• Predation an interaction in which one organism
  eats another
• Predator doing the eating
• Prey being eaten
• Both predator and prey have evolved with
  adaptations to enhance survival
• Ex camouflage, hunting in packs, warning
  coloration

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Prey adaptations
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Population interactions

• Symbiotic relationships a close relationship
  between species in which one of the species lives
  in or on the other
• Parasitism the parasite obtains food at the
  expense of the other organism (host)
• Mutualism both organisms benefit
• Commensalism one organisms benefits and the
  other is neither helped nor harmed

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Parasitism blowfly larvae kill purple martin
chick
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Mutualism sea anemone protects clownfish from
predators clownfish is territorial and protects
anemone from predators and shares food
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Commensalism grey whale carries barnacles
whale not harmed nor helped, barnacles have more
access to food
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Disturbances in communities

• Ecological succession community change when new
  species colonize disturbed area
• Primary succession community arises in lifeless
  area without soil
• Ex volcano creating new island
• Secondary succession community arises in
  disturbed area with soil
• Ex growth in plowed farm field

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Primary succession growth on lava rock
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Secondary succession after forest fire
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Disturbances in communities

• Pioneer species predominant species in the
  early stages of succession tend to be small,
  fast-growing, and fast-producing
• Succession proceeds through many stages until it
  reaches a stable end point called the climax
  community

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Pioneer species can grown on rock and will help
form soil