The Biomes of Earth

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Population Ecology
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Biodiversity

• Biodiversity variety of organisms in a given
  area
• Review food web
• All ecology linked

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Population Growth

1. Population- all the individuals of a species
   living together in one place at one time.
2. Demographics- the statistical study of
   populations.
3. Populations size- the number of individuals in
   the population.
4. Population density- the number of individuals
   that live in a given area.

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Population Dispersion

• Uniform-Territoriality and competition for
  resources lead to individuals living a specific
  distance apart.
• Random- Individuals spread randomly in an area.
• Clumped- Individual live close together in group
  to help with mating, gain protection, or access
  resources.

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Population growth

• Currently 6 billion people
• Growth rate 90 million per year
• Not enough resources
• Water, gas, electricity
• space

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Growth Rates

• Exponential growth curve- growth is constant and
  increasing steadily resulting in a J-shape curve.
• Limiting factors-predators, disease, resources

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Growth Rates

• r-Strategists- populations that
• grow very fast
• have short life spans
• reproduce quickly
• no parental care
• live in an unstable environment
• ex. Insects

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Growth Rates

• k-Strategist- populations that . . .
• grow slowly
• live a longer life
• reproduce later in life and fewer times
• lots of parental care
• live in stable environments
• ex Large mammals

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Growth Rates

• Carrying capacity (K)-
• maximum occupancy
• the maximum number of individuals of a particular
  species that the environment can normally and
  consistently support.

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Survivorship curves
Type I Type II Type III
Birth rate High Medium High
Mortality rate (infant) Low Medium High
Parental care High Medium none
examples Large mammals (humans) Small mammals, rodents Invertebrates, fish, amphibians, plants
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Influences on Growth RatesLimiting Factors

• Density dependent factors- water, food,, shelter,
  competition, predation, parasitism and disease
• Density independent factors- weather and climate

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Population Evolution
How does a population change?

• Mutations- it happens at a very slow rate and is
  the source of all variation. Mutations occur in
  the DNA.
• Gene Flow- movement of individuals into a new
  population (immigration) or out of a population
  (emigration).
• Genetic Drift- a reduction in a particular trait
  due to a random chance event like a fire. The
  allele frequency for a trait may be severely
  affected.

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• Nonrandom mating- also known as artificial
  selection includes, inbreeding, self pollination,
  or mates being selected for a particular trait.
  Farmers will mate only the best producing milk
  cows. All of the above lead to a population with
  less variation and an emphasis on a particular
  trait.

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Population problem

• Impound already existing problems
• Habitat fragmentation

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Population problem

• Impound already existing problems
• Pollution (Possible cause of deformations)

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Population problem

• Impound already existing problems
• Pollution (Increase health risks)
• Los Angeles and Mexico City

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Population problem

• Impound already existing problems
• Pollution (Harming other species)
• Sea Lion caught in fishing net

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Population problem

• Impound already existing problems
• Decrease in biodiversity
• extinction 1987 dusky seaside sparrow
• Endangered species Bengal Tiger

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Population problem

• Impound already Decrease in biodiversity
• extinction hunting and illegal commercial
  harvesting

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Population problem

• Impound already existing problems
• Deforestation
• possible medicines
• Affects carbon cycle