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Questions and Answers
What is primary productivity?
Primary productivity is the rate at which solar energy is converted into organic compounds via photosynthesis over a unit of time.
What is GPP?
Gross primary productivity is the total rate of photosynthesis in a given area.
What is NPP?
Net primary productivity is the rate of energy storage by photosynthesizers in a given area after subtracting the energy lost to respiration.
What is productivity measured in?
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Describe how light is absorbed in aquatic ecosystems.
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What factor do ecosystems depend on?
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What cycles are essential for life on earth?
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Describe how energy flows in terrestrial and aquatic ecosystems.
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Describe the 10% rule.
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How can the loss of energy be explained in an ecosystem?
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What is a food web?
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Describe positive and negative feedback loops.
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Describe trophic cascades.
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Study Notes
Primary Productivity
- Primary productivity quantifies the conversion of solar energy into organic compounds via photosynthesis over time.
- Gross primary productivity (GPP) represents the total photosynthesis rate in a specific area.
- Net primary productivity (NPP) measures energy stored by photosynthetic organisms after accounting for energy lost to respiration.
Measurement and Factors
- Productivity is commonly expressed in units like kcal/m²/year.
- Ecosystems rely on continuous high-quality energy flows to maintain structure and function, facilitating biogeochemical cycles.
Light Absorption in Aquatic Ecosystems
- Red light significantly dissipates within the upper meter of water, while blue light penetrates deeper than 100 meters in clear waters.
- Photosynthesizers in aquatic environments are adapted to low visible light availability.
Energy Flow
- Energy transitions from the sun to producers at the lowest trophic levels, and then to higher trophic levels in both terrestrial and marine ecosystems.
- The 10% rule indicates that only about 10% of energy is transferred from one trophic level to the next.
Energy Loss in Ecosystems
- Energy loss during trophic transitions can be explained by thermodynamic laws, emphasizing inefficiencies in energy transfer.
Food Webs
- A food web illustrates interconnected food chains, demonstrating the flow of energy and nutrients among multiple species.
Feedback Loops and Trophic Cascades
- Positive and negative feedback loops impact food webs, with species changes altering ecosystem dynamics.
- Trophic cascades occur when top predators are added or removed, leading to significant alterations in predator-prey relationships and ecosystem structure.
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Description
Explore the concepts of primary productivity, including gross and net primary productivity, and their importance in ecosystems. Learn how light absorption affects photosynthesis in aquatic environments and the flow of energy through trophic levels.
