Ecosystem Energy Flow & Chemical Cycling Explained | Chapter 55 of Campbell Biology

Ecosystem Energy Flow & Chemical Cycling Explained | Chapter 55 of Campbell Biology

Book cover

How does energy move through ecosystems, and how are essential nutrients recycled? Chapter 55 of Campbell Biology unpacks the dynamic processes of energy flow and chemical cycling, explaining how life on Earth depends on the transfer and transformation of energy and matter. This chapter is essential for understanding both natural ecosystem function and how human actions can impact global cycles.

Watch the full podcast summary below, then read on for an in-depth breakdown, key terms, and applied examples in modern ecology and environmental science.

Energy Flow in Ecosystems

Energy in ecosystems follows the laws of thermodynamics: it enters as sunlight, is captured by autotrophs (primary producers), and is transferred through trophic levels via consumers and decomposers. Gross primary production (GPP) measures total energy captured by producers, while net primary production (NPP) is the energy available to consumers after producers’ respiration.

  • Primary Production: Autotrophs convert sunlight to chemical energy. NPP varies by ecosystem and is limited by factors like sunlight, nutrients, and water.
  • Energy Transfer: Only about 10% of energy is passed from one trophic level to the next—most is lost as heat. Ecological pyramids show the decline in energy or biomass up food chains.
  • Secondary Production: Energy from consumers used to build new biomass, such as growth and reproduction.

Chemical Cycling: The Biogeochemical Cycles

Biogeochemical cycles move essential elements between living (biotic) and nonliving (abiotic) components of ecosystems. Key cycles include:

  • Carbon Cycle: Movement of carbon through photosynthesis, respiration, decomposition, and human activities. Ecosystems that absorb more carbon than they release are carbon sinks.
  • Nitrogen Cycle: Transformation of nitrogen via processes like nitrogen fixation, nitrification, and denitrification—often mediated by bacteria.
  • Phosphorus Cycle: Movement of phosphorus from rocks, through organisms, and back to the soil and water.
Decomposers play a crucial role by breaking down organic matter and releasing nutrients for reuse in the ecosystem.

Human Impact and Restoration Ecology

Humans affect ecosystem processes through activities like agriculture, pollution, and deforestation. Eutrophication—nutrient enrichment leading to algal blooms—can disrupt aquatic ecosystems. Bioremediation uses living organisms to detoxify polluted environments, while restoration ecology seeks to repair and sustain damaged ecosystems for the future.

Key Glossary Terms

  • Abiotic Factors: Nonliving environment components.
  • Autotrophs: Primary producers (e.g., plants, algae).
  • Biogeochemical Cycles: Cycling of elements like carbon, nitrogen, and phosphorus.
  • Decomposers: Organisms recycling nutrients by breaking down dead matter.
  • Gross Primary Production (GPP): Total energy captured by producers.
  • Net Primary Production (NPP): Energy available to consumers.
  • Nutrient Cycling: Movement of essential elements through ecosystems.
  • Trophic Levels: Steps in the food chain (producers, consumers, decomposers).
  • Trophic Efficiency: Percentage of energy transferred between trophic levels.
  • Restoration Ecology: Restoring degraded ecosystems.
  • Secondary Production: New biomass generated by consumers.
  • Eutrophication: Nutrient over-enrichment leading to ecological disruption.
  • Biomass: Total living mass in a given area.
  • Carbon Sink: Ecosystem absorbing more CO2 than it releases.
  • Bioremediation: Using organisms to clean up pollution.

Conclusion: Why Ecosystem Energy Flow and Chemical Cycling Matter

Understanding how energy and matter move through ecosystems reveals the deep interconnectedness of life and environment. These cycles sustain life, support ecosystem services, and highlight the importance of conservation and restoration in the face of human-driven change.

Watch the podcast above for a complete explanation, and subscribe to Last Minute Lecture for more Campbell Biology chapter guides and academic resources.

For more textbook chapter breakdowns, visit the Last Minute Lecture channel and subscribe for regular educational content and study guides.

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