Lecture Notes: Ecosystems and Energy Transfer

Introduction to Ecosystems

• Ecosystem Definition: A space defined by interacting components, both living (biotic) and non-living (abiotic).
• Types of Ecosystems:
  • Open Ecosystem: Allows movement of both energy and matter (e.g., forests).
  • Closed Ecosystem: Restricts movement of matter, but allows energy (e.g., sealed mesocosms).

Energy in Ecosystems

• Sunlight as Primary Energy Source:
  • Drives most ecosystems by providing energy through solar radiation.
  • Organisms utilize sunlight to convert it into chemical energy.
• Exceptions:
  • Some ecosystems like caves or deep ocean areas do not rely on sunlight.

Food Chains and Food Webs

• Food Chain:
  • Demonstrates feeding relationships and energy transfer between organisms.
  • Example: Grass → Grasshopper → Mouse → Owl.
• Food Web:
  • More comprehensive; considers all possible feeding interactions in an ecosystem.

Decomposers and Energy

• Decomposers:
  • Break down dead organisms and organic waste.
  • Include bacteria and fungi.
  • Essential for returning carbon compounds to the ecosystem.

Autotrophs vs. Heterotrophs

• Autotrophs:
  • Create their own food from inorganic substances (self-feeding).
  • Photoautotrophs: Use sunlight (e.g., plants, algae).
  • Chemoautotrophs: Use chemical reactions (e.g., certain bacteria like Acidithiobacillus ferrooxidans).
• Heterotrophs:
  • Obtain energy by consuming other organisms.
  • Include animals and humans.
  • Assimilation: Process of absorbing nutrients from consumed organisms.

Trophic Levels

• Definition: Levels that describe an organism's position in a food chain/web.
• Classification:
  • Producers: Autotrophs.
  • Primary Consumers: Eat producers.
  • Secondary and Tertiary Consumers: Eat other consumers.
• Complexity in Food Webs: Organisms can occupy multiple trophic levels.

Energy Pyramids

• Structure:
  • Base with producers, higher levels with consumers.
  • Illustrate energy distribution among trophic levels.
• Energy Loss:
  • About 90% of energy is lost between levels (e.g., through heat).
  • Only 10% of energy moves to the next level.
• Implications:
  • Limits the length of food chains.
  • Restricts population sizes at higher trophic levels.

Conclusion

• Understanding energy movement is crucial for ecology.
• Key takeaways include concepts of energy loss and the role of decomposers.
• Ecosystems are dynamic and complex, with interactions across various levels.