Population Ecology

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Population Ecology
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CHAPTER
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Finding Gold in a Costa Rican Cloud Forest

• Golden toads lived in Costa Ricas Monteverde
  cloud forest.
• Golden toads were first described in 1964. They
  were extinct by 1989.

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Lesson 4.1 Studying Ecology

• Ernst Haeckel defined ecology in 1866 as the
  body of knowledge concerning the economy of
  naturethe total relations of the animal to both
  its inorganic and organic environment.

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Levels of Ecological Organization
Lesson 4.1 Studying Ecology

• The study of how organisms interact with each
  other and with their environments
• Scientists study ecology at various levels of
  organization.

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Biotic and Abiotic Factors
Lesson 4.1 Studying Ecology

• Biotic factors Parts of an ecosystem that are
  living or used to be living
• Abiotic factors Parts of an ecosystem that have
  never been living

Did You Know? Decaying organisms are biotic
factors as long as their structure remains
cellular.
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Habitat
Lesson 4.1 Studying Ecology

• The specific environment in which an organism
  lives
• Habitats provide an organism with
  resourcesanything an organism needs to survive
  and reproduce, including food, shelter, and
  mates.

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Lesson 4.2 Describing Populations

• From 1900 to 2000, the white-tailed deer
  population of New York state grew from about
  20,000 to more than 1 million. Densities of more
  than 100 deer per sq mi occur in some
  metropolitan areas.

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By counting the number of birds passing by a
point per second, (several trials), ecologists
estimated the size of one passenger pigeon flock
at 2 billion pigeons. The flock required over
5 hours to fly past the counting location!
birds X 3600 seconds X 5hours 1second
1 hour total population size!
100 years later 0
passenger pigeons
One flock in 1866 in southern Ontario was
described as being 1 mi (1.5 km) wide and 300 mi
(500 km) long, took 14 hours to pass, and held in
excess of 3.5 billion birds. John James Audubon
recounted a mile-wide flock of migrating
passenger pigeons that passed overhead, blocking
the sun for 3 days!
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This photo shows how several ecologists sample a
strip of an albatross nesting site. Average
birds/strip X strips in nesting site
nesting albatross
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Use this sample data to estimate the size of
populations

• 111,000 carrier pigeons fly over per second
• The flock flies over for 5 hours (3600
  seconds/hr)
• 111000 birds X 3600 seconds X 5 hours 2
  billion birds
• sec 1 hour
• 1000 toads X 2000 Ha 2 million
  toads
• 1 Ha

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Population DensityMeasure of how crowded a
population is
Low population density
benefits Less competition for resources
disadvantages finding mates can be
difficult more vulnerability to predators High
population density
benefitsFinding mates is easier Safety in
numbers versus predation
disadvantages more competition for resources
more rapid spread of infectious diseasse
Northern pintail ducks
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Population Distribution

• How organisms are arranged within an area
• Random distribution no particular pattern
• Uniform distribution evenly spaced
• Clumped distribution grouped near resources
  most common

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Age Structure

• number ?? in each age group
• used to predict future population growth

Most people will still have more
children. Characteristic of developing nations
with low wealth low levels of female education
Most people will not have more children. e.g.,
China (sudden reduction in birth rate?lower
young)
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Lesson 4.3 Population Growth

• From 1800 to today, the human population has
  grown from about 1 billion to more than 6.8
  billionan exponential rate of increase.

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The rate of population growth is ( individuals
added/year - individuals lost/year)total
individuals at the beginning of the year

• 2 ways to add individuals
• immigration
• birth
• 2 ways to lose individuals
• emigration
• death

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Immigration and Emigrationimmigrate into a
regionexit by emigration
Lesson 4.3 Population Growth

• Migration, seasonal movement into and out of an
  area, can temporarily affect population size.

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Calculating Population Growth
Lesson 4.3 Population Growth

• Determined by the following equation
  (birthrate immigration rate) (death rate
  emigration rate)
• Growing populations have a positive growth rate
  shrinking populations have a negative growth
  rate.
• Usually expressed in terms of individuals per 1000

Did You Know? Immigration contributes more than 1
million people to the U.S. population per year.
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Exponential Growth
Lesson 4.3 Population Growth

• Population increases by a fixed percentage
  every year.
• Normally occurs only when small populations are
  introduced to an area with ideal environmental
  conditionsno limiting factors
• Rarely lasts longat a certain population size,
  competition for resources increases.

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Logistic Growth
Lesson 4.3 Population Growth

• Growth almost always slows and stops due to
  limiting factors.
• Size of population stabilizes at a number the
  environments
• resources can sustain The Carrying capacity
• Limiting factors
• Density-dependent Influence changes with
  population density.
• e.g., competition resources,
• predator success, Rate of infectious
• disease spread
• Density-independent Influence does not change
  with
• population density.
• e.g., natural disasters, manmade
• disasters

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Biotic Potential
Lesson 4.3 Population Growth

• An organisms maximum ability to produce
  offspring in ideal conditions
• Many factors influence biotic potential,
  including gestation time and generation time.
• Organisms with high biotic potential can recover
  more quickly from population declines than
  organisms with low biotic potential.

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Population Crash

• When a population grows so rapidly that within
  one or a few generations, it grows far above the
  carrying capacity of the ecosystem, then the size
  of the population may drop dramatically.
• During the period that the resources are being
  used at a higher than sustainable rate (more
  individuals than carrying capacity), then the
  recycling of matter can be disrupted, lowering
  the carrying capacity.
• Crashes normally occur for organisms with short
  lifespans, short gestations, and high s
  offspring/female.
• However, having technology that allows continued
  unsustainable human population growthby allowing
  extraction of resources like ground water or
  oilputs humans at risk for a population crash.
  What will happen if we use up these resourcesand
  cant get them even with technology?

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Golden toad population growth

• 1 Describe these levels of an ecosystem for
  golden toads
• Individual
• Population
• Species (name it)
• Community
• Ecosystem
• 2 required abiotic factors for this species
• 3 required biotic factors for this species
• 4 resources required for the species
• 5 Two reasons likely for the extinction of the
  toads

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