Environmental Biology - Ecosystems

Introduction to Ecosystems

• Focus on how ecosystems sustain human societies.
• Key concepts to understand:
  • Ecology
  • Hierarchy of biological organization
  • Ecosystem components and interactions
  • Energy transformations across trophic levels
  • Biogeochemical cycles
  • Abiotic and biotic interactions, symbiotic relationships

Case Study: Lake Washington

• Example of ecosystem balance:
  • Mid-1900s issue: lake turbid, fish dying due to nutrient-rich wastewater.
  • Phosphorus from sewage led to algae bloom, depleting oxygen.
  • Effluent control in 1965 led to decline in phosphorus and algae.
• Key takeaway: Interconnectedness of biotic and abiotic factors.

Ecology and Biological Organization

• Ecology: Study of organisms' interactions with their environment.
  • Interdisciplinary: Biology, geology, chemistry, etc.
• Hierarchy:
  • Species: Organisms of the same kind capable of reproduction.
  • Population: Group of same species in a specific area.
  • Community: Different species populations in an area.
  • Ecosystem: Interaction of community with abiotic elements.

Energy in Ecosystems

• Types of Energy:
  • Kinetic: Energy of motion.
  • Potential: Stored energy.
• Laws of Thermodynamics:
  • First Law: Conservation of energy.
  • Second Law: Entropy increases, reducing available energy.
• Energy Sources:
  • Sun: Primary source.
  • Primary Producers: Plants (photosynthesis), extremophiles (chemosynthesis).

Trophic Levels and Energy Transfer

• Trophic Levels:
  • Primary Producer: Plants, extremophiles.
  • Primary Consumer: Herbivores.
  • Secondary Consumer: Carnivores.
  • Tertiary Consumer: Top-level predators.
• Energy Transfer:
  • 10% of energy transferred between trophic levels.
  • Energy lost as heat or through metabolic processes.

Biogeochemical Cycles

• Water Cycle: Evaporation, precipitation, transpiration, percolation.
• Carbon Cycle: Photosynthesis, fossil fuels, carbon sinks (forests).
• Nitrogen Cycle:
  • Atmospheric nitrogen (N2) fixed by bacteria into usable forms.
  • Human impact: Fossil fuels, agriculture (eutrophication).
• Phosphorus Cycle: No atmospheric component, rocks, and fertilizer runoff.
• Sulfur Cycle: Volcanic emissions, fossil fuel burning, acid rain.

Biotic Interactions and Symbiotic Relationships

• Symbiotic Relationships:
  • Mutualism: Both organisms benefit (e.g., clownfish and anemone).
  • Commensalism: One benefits, other neutral (e.g., barnacles on turtles).
  • Parasitism: One benefits at the expense of the other (e.g., deer tick).
• Other Interactions:
  • Predation: Predator-prey dynamics.
  • Competition: For resources among or within species.
• Keystone Species: Crucial for ecosystem balance (e.g., gray wolf).

Homework and Additional Resources

• Read Chapter 5 in textbook.
• Watch Bozeman Biology video on biogeochemical cycles.
• Contact instructor for questions or office hours.