Questions and Answers
Define gross primary production (GPP) and net primary production (NPP).
Gross primary production is the amount of energy that autotrophs capture by photosynthesis and chemosynthesis per unit of time. Net primary production is the amount of energy per unit of time that producers capture by photosynthesis and chemosynthesis minus the amount they use in cellular respiration.
How does NPP vary with latitude?
Terrestrial NPP is highest in the tropics and declines in the north and south.
What is 'secondary production' and how is it related to heterotroph physiology?
Secondary production is energy derived from the consumption of organic compounds produced by other organisms. Heterotrophs obtain their energy in this manner.
Define allochthonous and autochthonous inputs to ecosystems, and give an example of each.
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What is a trophic pyramid?
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What is 'trophic efficiency'?
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How can biomass pyramids be inverted in aquatic ecosystems?
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What is the difference between 'bottom-up' and 'top-down' control of trophic cascades?
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Describe three factors that might affect the number of trophic levels in an ecosystem.
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What is meant by 'net interaction strength'?
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How is community or ecosystem stability affected by food web complexity?
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Define nitrification and denitrification.
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What is a nutrient cycle?
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Why do different nutrients cycle at different rates?
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What is meant by a 'nutrient spiral' in an aquatic ecosystem?
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What does it mean to say that conservation biology is a value-based discipline?
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What is meant by the 'background' extinction rate?
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What is 'taxonomic homogenization'?
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Study Notes
Gross and Net Primary Production
- Gross primary production (GPP) refers to total energy captured by autotrophs through photosynthesis and chemosynthesis over time.
- Net primary production (NPP) is the energy left after autotrophs use some for cellular respiration, measuring the energy available for consumers.
NPP Variability
- NPP is highest in tropical regions and decreases towards the poles.
- Yearly variations in NPP can indicate ecosystem health, indicating potential impacts from environmental stresses like drought or acid rain.
- NPP is connected to the global carbon cycle.
Secondary Production and Heterotrophs
- Secondary production is the energy obtained from consuming organic compounds produced by other organisms (heterotrophs).
- Heterotrophs are categorized based on their food sources.
Ecosystem Input Types
- Allochthonous inputs are external energy sources, such as plant material in aquatic ecosystems.
- Autochthonous inputs are energy produced within the ecosystem by autotrophs, like green plants and algae.
- Example: Bear Brook relies heavily on allochthonous inputs, while Mirror Lake capitalizes on autochthonous energy.
Trophic Pyramid and Efficiency
- A trophic pyramid illustrates energy or biomass levels across trophic layers, reflecting energy flow in ecosystems.
- Trophic efficiency is energy at one level divided by the energy at the level below, accounting for consumption and assimilation rates.
Inverted Biomass Pyramids
- In many aquatic ecosystems, primary producers (phytoplankton) may have shorter life spans, resulting in inverted biomass pyramids where heterotrophs outweigh autotrophs by biomass, though autotrophs produce more energy.
Trophic Cascade Controls
- Bottom-up control is influenced by NPP and resource availability, dictating energy flow upward through trophic levels.
- Top-down control focuses on consumption by predators affecting lower trophic levels' biomass and composition, leading to simultaneous operation of both control types in ecosystems.
Trophic Levels Influences
- Trophic levels depend on energy input through primary production.
- Disturbances, including diseases, influence population sustainability of higher predators.
- Ecosystem size affects biodiversity; larger areas may support more trophic levels due to larger populations.
Net Interaction Strength
- Describes the impact of one species on another’s population, capturing direct and indirect effects within food webs.
- Understanding interaction strengths aids in research and conservation efforts by clarifying key ecological links.
Food Web Complexity and Stability
- Complexity in food webs can enhance community stability, providing resilience against disturbances through interconnected species interactions.
Nutrification Processes
- Nitrification converts ammonia and ammonium to nitrate via nitrifying bacteria in aerobic conditions.
- Denitrification transforms nitrate back into nitrogen gas, facilitating nitrogen cycle completion under hypoxic conditions.
Nutrient Cycle Definition
- Nutrient cycles represent the exchange and movement of organic and inorganic matter, regulated by food webs and influenced by climate conditions.
- Nutrients vital for primary productivity cycle faster than those that are not limiting.
Nutrient Spiral in Aquatic Ecosystems
- Describes the upstream-downstream cycling of nutrients, characterized by repeated nutrient absorption and release along water flow.
Conservation Biology's Value Basis
- Conservation biology reflects human values and operates within societal contexts, requiring transparency about the values inherent in conservation practices.
Background Extinction Rate
- Refers to the natural rate of extinction over geological time, with current extinction rates greatly elevated compared to historical background levels.
Taxonomic Homogenization
- Describes the global decline in biodiversity from the spread of non-native species, leading to reduced native specialists and increased presence of generalists.
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Description
Explore key concepts in chapters 20 to 23 of BIOL 314, focusing on gross primary production (GPP) and net primary production (NPP). This quiz will help reinforce your understanding of energy capture in ecosystems and how various factors like latitude influence these processes.