3.2 Energy Flow and Nutrient Cycling
3 min read•august 9, 2024
Energy flow and nutrient cycling are vital processes that keep ecosystems running. They show how living things get and use energy, and how important elements move around in nature.
These processes are key to understanding how ecosystems work. They reveal the connections between living and non-living parts of the environment, and how energy and matter cycle through the natural world.
Energy Flow
Photosynthesis and Cellular Respiration
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- converts light energy into chemical energy stored in glucose
- Occurs in chloroplasts of plant cells and some bacteria
- Requires carbon dioxide, water, and sunlight as inputs
- Produces glucose and oxygen as outputs
- General equation: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
- breaks down glucose to release energy for cellular processes
- Takes place in mitochondria of all living cells
- Requires glucose and oxygen as inputs
- Produces carbon dioxide, water, and ATP as outputs
- General equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
Primary and Secondary Production
- refers to the creation of new organic matter by autotrophs
- (GPP) represents total energy fixed by photosynthesis
- (NPP) equals GPP minus energy used for respiration
- NPP available for consumption by heterotrophs
- involves the creation of biomass by heterotrophs
- Consumers convert a portion of consumed energy into their own tissues
- measures the transfer of energy between trophic levels
- Typically only 10% of energy transfers to the next trophic level
- Energy loss occurs through heat, movement, and undigested material
- illustrate energy transfer and biomass distribution (energy pyramids, biomass pyramids, numerical pyramids)
Nutrient Cycling
Biogeochemical Cycles Overview
- describe the movement of elements through ecosystems
- Involve biotic and abiotic components of the environment
- Cycles can be gaseous (carbon, nitrogen) or sedimentary (phosphorus)
- store elements for long periods (atmosphere, oceans, rocks)
- allow for rapid cycling of elements (soil, living organisms)
- represent the movement of elements between reservoirs and exchange pools
- Human activities often disrupt natural biogeochemical cycles
Carbon and Nitrogen Cycles
- moves carbon through atmosphere, biosphere, hydrosphere, and lithosphere
- Atmospheric carbon dioxide fixed by plants through photosynthesis
- Respiration and release carbon back into the atmosphere
- Fossil fuel combustion increases atmospheric carbon dioxide levels
- Ocean serves as a major , absorbing CO₂ from the atmosphere
- involves conversion of nitrogen gas to biologically available forms
- by bacteria converts N₂ to ammonia
- converts ammonia to nitrites and then nitrates
- returns nitrogen to the atmosphere as N₂
- Human activities like fertilizer use and fossil fuel combustion alter the nitrogen cycle
Phosphorus and Water Cycles
- primarily occurs in soil and water
- Weathering of rocks releases phosphorus into soil and water bodies
- Plants absorb phosphorus from soil through their roots
- Animals obtain phosphorus by consuming plants or other animals
- Decomposition returns phosphorus to soil or water
- Phosphorus can become limiting in aquatic ecosystems
- (hydrologic cycle) describes the continuous movement of water on Earth
- Processes include evaporation, transpiration, condensation, precipitation, and runoff
- Solar energy drives the water cycle
- Oceans contain 97% of Earth's water
- Freshwater resources crucial for terrestrial ecosystems and human use
- Climate change affects precipitation patterns and water availability globally
Key Terms to Review (24)
Biogeochemical cycles: Biogeochemical cycles refer to the natural processes that recycle nutrients in various chemical forms from the environment to organisms and back again. These cycles are essential for maintaining ecosystem balance and support life by ensuring the continuous availability of vital elements such as carbon, nitrogen, phosphorus, and water. Through interactions between living organisms and Earth's spheres—like the atmosphere, hydrosphere, lithosphere, and biosphere—these cycles illustrate how energy and matter flow within ecosystems.
Biomass pyramid: A biomass pyramid is a graphical representation that illustrates the distribution of biomass among different trophic levels in an ecosystem. It typically shows that the total biomass decreases as one moves up the pyramid from producers to primary consumers, secondary consumers, and so on. This pattern highlights the inefficiencies in energy transfer between trophic levels, where a significant amount of energy is lost at each stage, emphasizing the importance of producers in supporting the entire ecosystem.
Carbon cycle: The carbon cycle is the continuous movement of carbon among the Earth's atmosphere, oceans, soil, and living organisms. This cycle is crucial for regulating Earth's climate and supporting life by facilitating energy flow and nutrient cycling through various processes like photosynthesis, respiration, and decomposition. It connects to climate regulation by influencing the levels of carbon dioxide in the atmosphere, which in turn affects global temperatures and climate patterns.
Carbon sink: A carbon sink is a natural or artificial reservoir that absorbs and stores carbon dioxide (CO2) from the atmosphere, helping to mitigate climate change. Carbon sinks play a critical role in the global carbon cycle by sequestering carbon, which can be stored in various forms such as plant biomass, soils, and oceans. These systems not only remove CO2 from the air but also contribute to energy flow and nutrient cycling by influencing ecosystem productivity and health.
Cellular respiration: Cellular respiration is a metabolic process that converts biochemical energy from nutrients into adenosine triphosphate (ATP), and releases waste products. This process is essential for all living organisms, as it provides the energy needed for various cellular functions and plays a crucial role in the flow of energy and the cycling of nutrients within ecosystems.
Decomposition: Decomposition is the natural process through which organic matter, such as dead plants and animals, is broken down into simpler substances by decomposers like bacteria and fungi. This process is vital for recycling nutrients back into the ecosystem, allowing for energy flow and maintaining soil fertility, which plays a significant role in nutrient cycling.
Denitrification: Denitrification is the microbial process through which nitrates ($$NO_3^-$$) and nitrites ($$NO_2^-$$) are reduced to nitrogen gas ($$N_2$$) or, to a lesser extent, nitrous oxide ($$N_2O$$), returning nitrogen to the atmosphere. This process plays a crucial role in the nitrogen cycle by removing excess nitrogen from ecosystems, thus preventing pollution and contributing to nutrient cycling, especially in aquatic environments.
Ecological Pyramids: Ecological pyramids are graphical representations that illustrate the distribution of energy, biomass, or the number of organisms at different trophic levels in an ecosystem. They help visualize how energy flows through an ecosystem and how nutrients cycle among various organisms, highlighting the efficiency of energy transfer from one level to the next.
Energy pyramid: An energy pyramid is a graphical representation that shows the flow of energy through different trophic levels in an ecosystem. It illustrates how energy decreases as it moves from producers at the base to various levels of consumers at the top, emphasizing the efficiency of energy transfer and the limitations in supporting higher trophic levels due to energy loss.
Exchange pools: Exchange pools refer to the specific components within ecosystems where nutrients and energy are temporarily stored before being transferred between different biotic and abiotic elements. These pools play a crucial role in maintaining the balance of ecosystems by facilitating nutrient cycling and energy flow, ensuring that essential elements like carbon, nitrogen, and phosphorus are available for organisms to use in various metabolic processes.
Fluxes: Fluxes refer to the rates at which energy and nutrients move through ecosystems. They represent the dynamic processes of transfer and transformation that occur as energy and materials cycle through different components of an ecosystem, such as organisms, soil, and atmosphere. Understanding fluxes is crucial for grasping how ecosystems function and maintain balance.
Gross Primary Production: Gross primary production (GPP) refers to the total amount of organic matter produced by photosynthetic organisms, such as plants and phytoplankton, in a given area over a specified time period. This process is fundamental to energy flow and nutrient cycling, as it serves as the primary energy source for all organisms within an ecosystem. GPP represents the energy captured by autotrophs through photosynthesis, which is then available to support the food web and maintain ecological balance.
Net primary production: Net primary production (NPP) is the amount of organic matter or biomass produced by plants through photosynthesis, minus the energy used by them for respiration. NPP is a crucial concept as it represents the energy available for consumers in an ecosystem and is a key factor in understanding energy flow and nutrient cycling, showing how energy moves through ecosystems and how nutrients are recycled within them.
Nitrification: Nitrification is the biological process by which ammonia is converted into nitrites and then into nitrates, primarily by specialized bacteria in the soil. This process plays a crucial role in the nitrogen cycle, transforming nitrogen compounds into forms that plants can absorb and use for growth, thus linking the dynamics of energy flow and nutrient cycling in ecosystems.
Nitrogen cycle: The nitrogen cycle is the process through which nitrogen is converted between its various chemical forms in the environment, including the atmosphere, soil, and living organisms. This cycle plays a crucial role in maintaining ecosystem health by ensuring that nitrogen is available for plant growth and, subsequently, for the animals that rely on those plants as a food source. The cycle involves several key processes, including nitrogen fixation, nitrification, denitrification, and ammonification, all of which contribute to nutrient cycling in ecosystems.
Nitrogen fixation: Nitrogen fixation is the process of converting atmospheric nitrogen gas (N₂) into a form that plants can use, such as ammonia (NH₃). This transformation is essential for making nitrogen available to living organisms, as most cannot utilize atmospheric nitrogen directly. Nitrogen fixation plays a vital role in nutrient cycling and energy flow within ecosystems, linking the nitrogen cycle to plant growth and productivity.
Numerical pyramid: A numerical pyramid is a graphical representation that illustrates the number of individuals at each trophic level in an ecosystem. This pyramid helps to visualize how population sizes decrease as one moves up through the levels, indicating the balance of energy flow and nutrient cycling within an ecological community.
Phosphorus cycle: The phosphorus cycle is the series of processes by which phosphorus moves through the environment, including the soil, water, and living organisms. Unlike other cycles, phosphorus does not have a gaseous phase and primarily exists in solid forms, such as phosphates. This cycle is crucial for life as it is a key component of DNA, RNA, and ATP, connecting it to the essential flow of energy and nutrients within ecosystems.
Photosynthesis: Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose, using carbon dioxide and water. This process not only produces the organic compounds that serve as food for these organisms but also releases oxygen as a byproduct, playing a crucial role in maintaining atmospheric balance and supporting life on Earth.
Primary Production: Primary production is the process by which autotrophs, such as plants and phytoplankton, convert sunlight or inorganic chemicals into organic matter through photosynthesis or chemosynthesis. This process is crucial for energy flow and nutrient cycling within ecosystems, as it forms the base of the food web, supporting all other trophic levels and facilitating the transfer of energy and nutrients throughout the ecosystem.
Reservoirs: Reservoirs are natural or artificial storage locations where water, nutrients, or energy are held and cycled within ecosystems. They play a crucial role in the flow of energy and cycling of nutrients, acting as crucial hubs that facilitate interactions among different components of the environment, including biotic and abiotic factors. By holding and releasing materials, reservoirs help maintain balance in ecosystems, influencing the availability of resources for organisms.
Secondary production: Secondary production refers to the generation of biomass by heterotrophic organisms, such as animals and microbes, through the consumption of primary producers or organic matter. This process is vital for energy transfer within ecosystems, as it converts the energy stored in primary production into a form that can be utilized by higher trophic levels, playing a crucial role in energy flow and nutrient cycling.
Trophic efficiency: Trophic efficiency refers to the proportion of energy that is transferred from one trophic level to the next in an ecosystem. It highlights how much energy is available to organisms at higher levels in the food chain, emphasizing the loss of energy due to metabolic processes, growth, and waste. This concept is crucial for understanding energy flow and nutrient cycling within ecosystems, as it impacts species abundance and community structure.
Water cycle: The water cycle is the continuous process by which water moves through the environment, transitioning between different states: liquid, vapor, and solid. This cycle is vital for distributing energy and nutrients across ecosystems, impacting weather patterns and supporting all life forms on Earth.