Unit 4: Functional Ecology
1. Principles and Models of Energy Flow
Energy flow is a fundamental process that governs the functioning of all ecosystems. Unlike matter, energy flows in a unidirectional manner through trophic levels.
Key Principles:
- Thermodynamic Laws: Energy flow follows the laws of thermodynamics; energy is neither created nor destroyed, and in every transfer, some energy is lost as heat.
- Energy Models: Ecosystems use various models to describe flow, such as the single-channel energy model or the Y-shaped model, which includes both grazing and detritus food chains.
2. Production and Productivity
Production refers to the total amount of organic matter created, while productivity is the rate of that creation.
Levels of Productivity:
- Primary Productivity: The rate at which energy is bound by producers (green plants).
- Gross Primary Productivity (GPP): Total rate of photosynthesis, including the energy used in respiration.
- Net Primary Productivity (NPP): The energy remaining after plant respiration (GPP - Respiration = NPP).
- Secondary Productivity: The rate of energy storage at the consumer levels (herbivores and carnivores).
3. Ecological Efficiencies and Energetics
Ecological energetics is the study of energy intake and expenditure in an ecosystem.
Ecological Efficiency:
- This is the efficiency with which energy is transferred from one trophic level to the next.
- Typically, only about 10% of the energy is stored as biomass in the next level, while the rest is lost to metabolic processes and heat.
4. Biogeochemical Cycles (C, N, S, and Water)
Biogeochemical cycles are the pathways by which chemical substances move through biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth.
[Image of the global nitrogen cycle]
Major Cycles:
- Carbon Cycle (C): Involves the exchange of carbon between the atmosphere and organisms through photosynthesis and respiration.
- Nitrogen Cycle (N): Includes processes such as nitrogen fixation, nitrification, and denitrification to make nitrogen available for life.
- Sulphur Cycle (S): Involves the movement of sulphur through the weathering of rocks and biological activity.
- Water Cycle: The continuous movement of water through evaporation, transpiration, condensation, and precipitation.
5. Microbial Ecology
Microbial ecology is the study of microbes in their environment and their interactions with each other and their surroundings. Microbes play a vital role as decomposers, recycling nutrients back into the biogeochemical cycles.
6. Exam Focus: Tips and FAQs
Exam Tip: Always remember that while energy flows linearly and is lost as heat, nutrients cycle repeatedly through the ecosystem. This is a frequent comparison question in exams.
Common Pitfalls
- Mistake: Confusing Production with Productivity. Correction: Production is an amount; Productivity is a rate over time.
- Mistake: Assuming the Nitrogen cycle is strictly atmospheric. Correction: Significant parts of the cycle occur in the soil via bacteria.
Frequently Asked Questions
Q: What is the 10% law in ecological energetics?
A: It states that only 10% of the energy available at one trophic level is passed on to the next; 90% is lost through heat and metabolism.
Q: Why are decomposers essential for functional ecology?
A: Without decomposers (microbial ecology), nutrients would remain locked in dead organic matter, and biogeochemical cycles would stop, eventually halting all life.