Ecology and the Biosphere

Population Ecology

  • Births and immigration add individuals to a population.
  • Deaths and emigration remove individuals from a population.
  • Population: A group of individuals of a single species living in the same general area.

Dispersion

  • Clumped: Individuals aggregate in patches (most common).
  • Uniform: Individuals are evenly distributed.
  • Random: Pattern of each individual is independent of other individuals (uncommon).

Mark-Recapture Method

  • Capture, tag, and release organisms.
  • Recapture a 2nd sample; note how many are marked.
  • Estimate population size: N=snxN = \frac{sn}{x}
    • Where:
      • s = number tagged and released
      • n = 2nd sample of individuals
      • x = number of marked in 2nd sample

Demography

  • Study of birth/death/migration rates of a population over time.
  • Life Tables:
    • Age-specific summary of survival and reproductive rates.
    • Follows the fate of a cohort (same-aged group from birth to death).

Survivorship Curves

  • Type I: Low death rates early/mid-life, sharp increase in older age (large mammals).
  • Type II: Constant death rate over lifespan (rodents, invertebrates).
  • Type III: High death rates in young, lower death rate for survivors (high offspring numbers, little to no care).

Exponential Population Growth

  • Describes population increase under idealized conditions.
  • Equation: dNdt=rN\frac{dN}{dt} = rN
    • where:
      • rr = rate of increase
      • NN = population size

Logistic Population Growth Model

  • Incorporates carrying capacity (K) to limit growth.
  • Equation: dNdt=rN(K−N)K\frac{dN}{dt} = rN \frac{(K - N)}{K}
    • where:
      • KK = Maximum population size the environment can support

Community Ecology

  • Focuses on interactions between species.
  • Community interactions:
    • Competition (-/-)
    • Predation (+/-)
    • Herbivory (+/-)
    • Parasitism (+/-)
    • Mutualism (+/+)
    • Commensalism (+/0)

Competitive Exclusion Theory

  • Two species competing for the same limiting resources cannot coexist.

Ecological Niche

  • Sum of a species’ use of abiotic and biotic resources in the environment.
  • Fundamental Niche: Potential niche without competition.
  • Realized Niche: Actual niche with competition.

Character Displacement

  • Characteristics are more divergent in sympatric populations than in allopatric populations.

Defensive Adaptations

  • Aposematic coloration (warning)
  • Cryptic coloration (camouflage)
  • Batesian mimicry (harmless mimics harmful)
  • Müllerian mimicry (two unpalatable species mimic each other)

Species Diversity

  • Trophic Structure: Feeding relationships between species.
  • Dominant Species: Most abundant or highest biomass.
  • Keystone Species: Not necessarily abundant, but exert strong control.
  • Ecosystem Engineers: Create or maintain physical structure.

Ecological Succession

  • Primary Succession: Occurs where no soil exists.
  • Secondary Succession: Occurs where soil still exists.

Ecosystems

  • Energy Flow: Energy enters as sunlight, is converted to chemical energy by autotrophs, then passes to heterotrophs as food and is dissipated as heat
  • Chemical Cycling: Chemicals cycled amongst abiotic and biotic components (inorganic elements assimilated into organisms)

Trophic Levels

  • Primary Producers: Autotrophs
  • Primary Consumers: Herbivores
  • Secondary, Tertiary, Quaternary Consumers: Carnivores
  • Decomposers: Recycle nutrients from all levels

Aquatic Biomes # Major Terrestrial Biomes

  • Lakes, Oceans, Intertidal Zones, Coral Reefs, Marine Benthic Zone, Wetlands, Streams & Rivers, Estuaries
    • Tropical Forest
    • Savanna
    • Desert
    • Chaparral
    • Temperate Grassland
    • Temperate Broadleaf Forest
    • Northern Coniferous Forest
    • Tundra
    • High Mountains
    • Polar Ice