Ecology Study Guide Notes

Intro to Ecology

  • Ecology: The study of interactions between organisms and their environment.
  • Models: Used to simplify complex systems, predict changes, and test hypotheses.
  • Biological Levels of Organization:
    1. Species (e.g., gray wolf)
    2. Population (e.g., pack of wolves)
    3. Community (wolves, deer, trees)
    4. Ecosystem (forest + all biotic/abiotic factors)
    5. Biome (e.g., temperate forest)
    6. Biosphere (Earth)
  • Spheres:
    • Atmosphere: Provides gases like oxygen, CO2CO_2.
    • Lithosphere: Supplies soil, nutrients.
    • Hydrosphere: Water for all life.
  • Biotic: Living components (e.g., bacteria, trees).
  • Abiotic: Nonliving components (e.g., sunlight, pH).

Energy Roles & Ecological Pyramids

  • Trophic Levels:
    1. Producers (plants)
    2. Primary consumers (herbivores)
    3. Secondary consumers (carnivores)
    4. Tertiary consumers (apex predators)
  • Energy Flow:
    • Sun -> Producers (via photosynthesis):
      6CO<em>2+6H</em>2O→C<em>6H</em>12O<em>6+6O</em>26CO<em>2 + 6H</em>2O \rightarrow C<em>6H</em>{12}O<em>6 + 6O</em>2
    • 10% rule: Only ~10% of energy is transferred to the next trophic level.
      • Example: 34,500 kcal -> 3,450 kcal -> 345 kcal -> 34.5 kcal
    • Higher trophic levels have fewer organisms due to energy loss.
  • Pyramids:
    • Numbers: Represents the number of organisms at each level.
    • Biomass: Represents the total mass of organisms at each level.
    • Energy: Represents the energy available at each level (always pyramid-shaped).

Trophic Cascades

  • Removal of a top predator causes ripple effects throughout the ecosystem.
    • Example: Removing wolves -> more deer -> fewer plants.

Keystone Species

  • Have a major impact on the ecosystem relative to their abundance.
    • Example: Sea otters control urchin populations; their removal disrupts ecosystem balance.

Population Growth

  • Growth Patterns:
    • Exponential: J-curve
    • Logistic: S-curve (carrying capacity)
    • Boom-Bust: Rapid growth followed by a crash.
  • Limiting Factors:
    • Dependent: Factors that depend on population size (e.g., disease, food availability).
    • Independent: Factors that affect populations regardless of size (e.g., fire, drought).
    • Abiotic changes affect whole ecosystems.

Biogeochemical Cycles

  • Matter cycles, while energy flows and is lost as heat.
  • Water Cycle:
    • Processes: Evaporation, Condensation, Precipitation, Run-off, Transpiration
  • Carbon Cycle:
    • Key Processes: Photosynthesis, Respiration, Decomposition, Combustion
    • Human Impact: Increased CO2CO_2 levels -> climate change
  • Nitrogen Cycle:
    • Nitrogen-fixing bacteria convert nitrogen into usable forms.
    • Nitrogen is used in proteins & DNA.
  • Phosphorus Cycle:
    • Phosphorus is released from rocks via weathering.
    • Needed for DNA, RNA, ATP
  • Eutrophication:
    • Excess nitrogen/phosphorus -> algae blooms -> oxygen depletion -> aquatic death

Disruptions

  • Cycle disruption causes chain effects.
    • Example: Fewer nitrogen-fixing bacteria -> poor plant growth -> affects all consumers.

Human Impact

  • Climate Change: More CO2CO_2 -> warming
  • Biomagnification: Toxins increase in concentration as they move up the food chain.
    • Apex predators are most affected (e.g., DDT in birds).